-
AIN_1P
AIN_1GND
AIN_2P
AIN_2GND
AIN_7P
AIN_7GND
AIN_8P
AIN_8GND
18-BitSARADC
2.5 VREF
REFGNDAGND
DVDDAVDD
ADS8598S
ADCDriver
REFIN/REFOUT
REFCAPB
REFSEL
Digital Filter
OS2
OS0
OS1
SAR Logic and
Digital ControlDB[15:0]
DOUTA
DOUTB
PAR/SER
RANGE
RD / SCLK
CS
RESET
CONVSTA, CONVSTB
FRSTDATA
STBY
REFCAPA
BUSY
1 M:Clamp
1 M:
3rd-OrderLPFClamp
PGA
ADCDriver
1 M:Clamp
1 M:
3rd-OrderLPFClamp
PGA
ADCDriver
1 M:Clamp
1 M:
3rd-OrderLPFClamp
PGA
ADCDriver
1 M:Clamp
1 M:
3rd-OrderLPFClamp
PGA
18-BitSARADC
18-BitSARADC
18-BitSARADC
SER/PAR Interface
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An IMPORTANT NOTICE at the end of this data sheet addresses
availability, warranty, changes, use in safety-critical
applications,intellectual property matters and other important
disclaimers. PRODUCTION DATA.
ADS8598SSBAS827 –SEPTEMBER 2017
ADS8598S 18-Bit, 200-kSPS, 8-Channel, Simultaneous-Sampling ADC
WithBipolar Inputs on a Single Supply
1
1 Features1• 18-Bit ADC With Integrated Analog Front-End•
Simultaneous Sampling: 8 Channels• Pin-Programmable Bipolar Inputs:
±10 V and ±5 V• High Input Impedance: 1 MΩ• 5-V Analog Supply:
2.3-V to 5-V I/O Supply• Overvoltage Input Clamp With 9-kV ESD•
Low-Drift, On-Chip Reference (2.5 V) and Buffer• Excellent
Performance:
– 200-kSPS Max Throughput on All Channels– DNL: ±0.5 LSB Typ;
INL: ±2.0 LSB Typ– SNR: 94 dB Typ; THD: −109 dB Typ
• Over Temperature Performance:– Max Offset Drift: 3 ppm/°C–
Gain Drift: 6 ppm/°C
• On-Chip Digital Filter for Oversampling• Flexible Parallel,
Byte, and Serial Interface• Temperature Range: –40°C to +125°C•
Package: LQFP-64
2 Applications• Monitoring and Control for Power Grids•
Protection Relays• Multi-Phase Motor Controls• Industrial
Automation and Controls• Multichannel Data Acquisition Systems
3 DescriptionThe ADS8598S device is an 8-channel, integrateddata
acquisition (DAQ) system based on a 18-bitsuccessive approximation
(SAR) analog-to-digitalconverter (ADC). All input channels
aresimultaneously sampled to achieve a maximumthroughput of 200
kSPS per channel. The devicefeatures a complete analog front-end
(AFE) for eachchannel, including a programmable gain amplifier(PGA)
with high input impedance of 1 MΩ, inputclamp, low-pass filter, and
an ADC input driver. Thedevice also features a low-drift, precision
referencewith a buffer to drive the ADC. A flexible
digitalinterface supporting serial, parallel, and parallel
bytecommunication enables the device to be used with avariety of
host controllers.
The ADS8598S can be configured to accept ±10-V or±5-V true
bipolar inputs using a single 5-V supply.The high input impedance
allows direct connectionwith sensors and transformers, thus
eliminating theneed for external driver circuits. The
highperformance and accuracy, along with zero-latencyconversions
offered by this device, also makes theADS8598S a great choice for
many industrialautomation and control applications.
Device Information(1)PART NUMBER PACKAGE BODY SIZE (NOM)ADS8598S
LQFP (64) 10.00 mm × 10.00 mm
(1) For all available packages, see the orderable addendum atthe
end of the datasheet.
Simplified Block Diagram
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Table of Contents1 Features
..................................................................
12 Applications
........................................................... 13
Description
............................................................. 14
Revision
History..................................................... 25 Pin
Configuration and Functions ......................... 36
Specifications.........................................................
5
6.1 Absolute Maximum Ratings
...................................... 56.2 ESD
Ratings..............................................................
56.3 Recommended Operating Conditions....................... 66.4
Thermal Information
.................................................. 66.5 Electrical
Characteristics........................................... 76.6
Timing Requirements: CONVST Control ................ 106.7 Timing
Requirements: Data Read Operation.......... 106.8 Timing
Requirements: Parallel Data Read Operation,
CS and RD Tied Together .......................................
106.9 Timing Requirements: Parallel Data Read Operation,
CS and RD Separate
............................................... 116.10 Timing
Requirements: Serial Data Read
Operation
.................................................................
116.11 Timing Requirements: Byte Mode Data Read
Operation
.................................................................
116.12 Timing Requirements: Oversampling Mode.......... 116.13
Timing Requirements: Exit Standby Mode............ 116.14 Timing
Requirements: Exit Shutdown Mode......... 126.15 Switching
Characteristics: CONVST Control ........ 126.16 Switching
Characteristics: Parallel Data Read
Operation, CS and RD Tied Together ..................... 126.17
Switching Characteristics: Parallel Data Read
Operation, CS and RD Separate .............................
136.18 Switching Characteristics: Serial Data Read
Operation
.................................................................
136.19 Switching Characteristics: Byte Mode Data Read
Operation
.................................................................
146.20 Typical Characteristics
.......................................... 18
7 Detailed Description
............................................ 257.1 Overview
.................................................................
257.2 Functional Block Diagram
....................................... 257.3 Feature
Description................................................. 267.4
Device Functional Modes........................................
35
8 Application and Implementation ........................ 488.1
Application Information............................................
488.2 Typical Applications
................................................ 48
9 Power Supply Recommendations ...................... 5310
Layout...................................................................
54
10.1 Layout Guidelines
................................................. 5410.2 Layout
Example .................................................... 54
11 Device and Documentation Support ................. 5611.1
Documentation Support ........................................
5611.2 Receiving Notification of Documentation Updates 5611.3
Community Resources..........................................
5611.4 Trademarks
........................................................... 5611.5
Electrostatic Discharge Caution............................ 5611.6
Glossary
................................................................
56
12 Mechanical, Packaging, and OrderableInformation
........................................................... 56
4 Revision History
DATE REVISION NOTESSeptember 2017 * Initial release.
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64A
IN_8
GN
D17
DB
1
1AVDD 48 AVDD
63A
IN_8
P18
DB
2
2AGND 47 AGND
62A
IN_7
GN
D19
DB
3
3OS0 46 REFGND
61A
IN_7
P20
DB
4
4OS1 45 REFCAPB
60A
IN_6
GN
D21
DB
5
5OS2 44 REFCAPA
59A
IN_6
P22
DB
6
6PAR/SER/BYTE_SEL 43 REFGND
58A
IN_5
GN
D23
DV
DD
7STBY 42 REFIN/REFOUT
57A
IN_5
P24
DB
7/D
OU
TA
8RANGE 41 AGND
56A
IN_4
GN
D25
DB
8/D
OU
TB
9CONVSTA 40 AGND
55A
IN_4
P26
AG
ND
10CONVSTB 39 REGCAP2
54A
IN_3
GN
D27
DB
9
11RESET 38 AVDD
53A
IN_3
P28
DB
10
12RD/SCLK 37 AVDD
52A
IN_2
GN
D29
DB
11
13CS 36 REGCAP1
51A
IN_2
P30
DB
12
14BUSY 35 AGND
50A
IN_1
GN
D31
DB
13
15FRSTDATA 34 REFSEL
49A
IN_1
P32
DB
14/H
BE
N
16DB0 33 DB15/BYTE_SEL
Not to scale
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Incorporated
5 Pin Configuration and Functions
PM Package64-Pin LQFP
Top View
Pin FunctionsPIN
TYPE DESCRIPTIONNAME NO.
AGND 2, 26, 35, 40,41, 47 P Analog ground pin.
AIN_1GND 50 AI Analog input channel 1: negative input.
AIN_1P 49 AI Analog input channel 1: positive input.
AIN_2GND 52 AI Analog input channel 2: negative input.
AIN_2P 51 AI Analog input channel 2: positive input.
AIN_3GND 54 AI Analog input channel 3: negative input.
AIN_3P 53 AI Analog input channel 3: positive input.
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Pin Functions (continued)PIN
TYPE DESCRIPTIONNAME NO.
AIN_4GND 56 AI Analog input channel 4: negative input.
AIN_4P 55 AI Analog input channel 4: positive input.
AIN_5GND 58 AI Analog input channel 5: negative input.
AIN_5P 57 AI Analog input channel 5: positive input.
AIN_6GND 60 AI Analog input channel 6: negative input.
AIN_6P 59 AI Analog input channel 6: positive input.
AIN_7GND 62 AI Analog input channel 7: negative input.
AIN_7P 61 AI Analog input channel 7: positive input.
AIN_8GND 64 AI Analog input channel 8: negative input.
AIN_8P 63 AI Analog input channel 8: positive input.
AVDD 1, 37, 38, 48 P Analog supply pin. Decouple this pin to the
closest AGND pins(see the Power Supply Recommendations
section).
BUSY 14 DO Active high digital output indicating ongoing
conversion(see the BUSY (Output) section).
CONVSTA 9 DI Active high logic input to control start of
conversion for first half count of device input channels (see
theCONVSTA, CONVSTB (Input) section).
CONVSTB 10 DI Active high logic input to control start of
conversion for second half count of device input channels (seethe
CONVSTA, CONVSTB (Input) section).
CS 13 DI Active low logic input chip-select signal (see the CS
(Input) section).
DB0 16 DO Data output DB0 (LSB) in parallel interface mode (see
the DB[6:0] section).
DB1 17 DO Data output DB1 in parallel interface mode (see the
DB[6:0] section).
DB2 18 DO Data output DB2 in parallel interface mode (see the
DB[6:0] section).
DB3 19 DO Data output DB3 in parallel interface mode (see the
DB[6:0] section).
DB4 20 DO Data output DB4 in parallel interface mode (see the
DB[6:0] section).
DB5 21 DO Data output DB5 in parallel interface mode (see the
DB[6:0] section).
DB6 22 DO Data output DB6 in parallel interface mode (see the
DB[6:0] section).
DB7/DOUTA 24 DOMulti-function logic output pin (see the
DB7/DOUTA section):this pin is data output DB7 in parallel and
parallel byte interface mode;this pin is a data output pin in
serial interface mode.
DB8/DOUTB 25 DOMulti-function logic output pin (see the
DB8/DOUTB section):this pin is data output DB8 in parallel
interface mode;this pin is a data output pin in serial interface
mode.
DB9 27 DO Data output DB9 in parallel interface mode (see the
DB[13:9] section).
DB10 28 DO Data output DB10 in parallel interface mode (see the
DB[13:9] section).
DB11 29 DO Data output DB11 in parallel interface mode (see the
DB[13:9] section).
DB12 30 DO Data output DB12 in parallel interface mode (see the
DB[13:9] section).
DB13 31 DO Data output DB13 in parallel interface mode (see the
DB[13:9] section).
DB14/HBEN 32 DIOMulti-function logic input or output pin (see
the DB14/HBEN section):this pin is data output DB14 in parallel
interface mode;this pin is a control input pin for byte selection
(high or low) in parallel byte interface mode.
DB15/BYTE SEL 33 DIOMulti-function logic input or output pin
(see the DB15/BYTE SEL section):this pin is data output DB15 (MSB)
in parallel interface mode;this pin is an active high control input
pin to enable parallel byte interface mode.
DVDD 23 P Digital supply pin; decouple with AGND on pin 26.
FRSTDATA 15 DO Active high digital output indicating data read
back from channel 1 of the device (see the FRSTDATA(Output)
section).
OS0 3 DI Oversampling mode control pin(see the Oversampling Mode
of Operation section).
OS1 4 DI Oversampling mode control pin(see the Oversampling Mode
of Operation section).
OS2 5 DI Oversampling mode control pin(see the Oversampling Mode
of Operation section).
PAR/SER/BYTE SEL 6 DI Logic input pin to select between
parallel, serial, or parallel byte interface mode (see the Data
ReadOperation section).
RANGE 8 DIMulti-function logic input pin (see the RANGE (Input)
section):when STBY pin is high, this pin selects the input range of
the device (±10 V or ±5 V); when the STBY pinis low, this pin
selects between the standby and shutdown modes.
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Incorporated
Pin Functions (continued)PIN
TYPE DESCRIPTIONNAME NO.
RD/SCLK 12 DIMulti-function logic input pin (see the RD/SCLK
(Input) section):this pin is an active-low ready input pin in
parallel and parallel byte interface;this pin is a clock input pin
in serial interface mode.
REFCAPA 44 AO Reference amplifier output pin. This pin must be
shorted to REFCAPB and decoupled to AGND using alow ESR, 10-µF
ceramic capacitor.
REFCAPB 45 AO Reference amplifier output pin. This pin must be
shorted to REFCAPA and decoupled to AGND using alow ESR, 10-µF
ceramic capacitor.
REFGND 43, 46 P Reference GND pin. This pin must be shorted to
the analog GND plane and decoupled withREFIN/REFOUT on pin 42 using
a 10-µF capacitor.
REFIN/REFOUT 42 AIOThis pin acts as an internal reference output
when REFSEL is high;this pin functions as input pin for the
external reference when REFSEL is low;decouple with REFGND on pin
43 using a 10-µF capacitor.
REFSEL 34 DI Active high logic input to enable the internal
reference(see the REFSEL (Input) section).
REGCAP1 36 AO Output pin 1 for the internal voltage regulator;
decouple separately to AGND using a 1-µF capacitor.
REGCAP2 39 AO Output pin 2 for the internal voltage regulator;
decouple separately to AGND using a 1-µF capacitor.
RESET 11 DI Active high logic input to reset the device digital
logic(see the RESET (Input) section).
STBY 7 DI Active low logic input to enter the device into one of
the two power-down modes: standby or shutdown(see the Power-Down
Modes section).
(1) Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. These are stress
ratingsonly, which do not imply functional operation of the device
at these or any other conditions beyond those indicated under
RecommendedOperating Conditions. Exposure to absolute-maximum-rated
conditions for extended periods may affect device reliability.
(2) Transient currents of up to 100 mA do not cause SCR
latch-up.
6 Specifications
6.1 Absolute Maximum Ratingsat TA = 25°C (unless otherwise
noted) (1)
MIN MAX UNITAVDD to AGND –0.3 7.0 VDVDD to AGND –0.3 7.0 VAnalog
input voltage to AGND (2) –15 15 VDigital input to AGND –0.3 DVDD +
0.3 VREFIN to AGND –0.3 AVDD + 0.3 VInput current to any pin except
supplies (2) –10 10 mA
TemperatureOperating –40 125
°CJunction, TJ 150Storage, Tstg –65 150
(1) JEDEC document JEP155 states that 500-V HBM allows safe
manufacturing with a standard ESD control process.(2) JEDEC
document JEP157 states that 250-V CDM allows safe manufacturing
with a standard ESD control process.
6.2 ESD RatingsVALUE UNIT
V(ESD) Electrostatic discharge
Human-body model (HBM),per ANSI/ESDA/JEDEC JS-001 (1)
All pins except analog inputs ±2000
VAnalog input pins only ±9000Charged-device model (CDM),per
JEDEC specification JESD22-C101 (2) ±500
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6.3 Recommended Operating Conditionsover operating free-air
temperature range (unless otherwise noted)
MIN NOM MAX UNITAVDD Analog supply voltage 4.75 5 5.25 VDVDD
Digital supply voltage 2.3 3.3 AVDD V
(1) For more information about traditional and new thermal
metrics, see the Semiconductor and IC Package Thermal Metrics
applicationreport.
6.4 Thermal Information
THERMAL METRIC (1)ADS8598S
UNITPM (LQFP)64 PINS
RθJA Junction-to-ambient thermal resistance 46.0 °C/WRθJC(top)
Junction-to-case (top) thermal resistance 7.8 °C/WRθJB
Junction-to-board thermal resistance 20.1 °C/WψJT Junction-to-top
characterization parameter 0.3 °C/WψJB Junction-to-board
characterization parameter 19.6 °C/WRθJC(bot) Junction-to-case
(bottom) thermal resistance N/A °C/W
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Incorporated
(1) Ideal input span, does not include gain or offset error.(2)
LSB = least significant bit.(3) This parameter is the endpoint INL,
not best-fit INL.(4) Gain error is calculated after adjusting for
offset error, which implies that positive full scale error =
negative full scale error = gain error ÷
2.
6.5 Electrical Characteristicsminimum and maximum specifications
are at TA = –40°C to +125°C, AVDD = 4.75 V to 5.25 V; typical
specifications are at TA= 25°C; AVDD = 5 V, DVDD = 3 V, VREF = 2.5
V (internal), and fSAMPLE = 200 kSPS (unless otherwise noted)
PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
ANALOG INPUTS
Full-scale input span (1)(AIN_nP to AIN_nGND)
RANGE pin = 1 –10 10V
RANGE pin = 0 –5 5
AIN_nP Operating input range,positive inputRANGE pin = 1 –10
10
VRANGE pin = 0 –5 5
AIN_nGND Operating input range,negative input All input ranges
–0.3 0 0.3 V
RIN Input impedance At TA = 25°C 0.85 1 1.15 MΩ
Input impedance drift All input ranges –25 ±7 25 ppm/°C
IIkg(in) Input leakage currentWith voltage at AIN_nP = VIN,all
input ranges (VIN – 2) / RIN µA
SYSTEM PERFORMANCE
Resolution 18 Bits
NMC No missing codes 18 Bits
DNL Differential nonlinearity All input ranges –0.9 ±0.5 0.9 LSB
(2)
INL Integral nonlinearity (3) All input ranges –5.5 ±2 5.5
LSB
EG Gain error (4)
All input ranges,externalreference
TA = –40°C to+85°C –256 ±10 256
LSBTA = –40°C to+125°C –256 ±10 300
All input ranges,internal reference ±10
Gain error matching(channel-to-channel)
Input range = ±10 V,external and internal reference 32 170
LSBInput range = ±5 V,external and internal reference 34 170
Gain error temperature drift
All input ranges,external reference –14 ±6 14
ppm/°CAll input ranges,internal reference ±10
EO Offset errorInput range = ±10 V –1.8 ±0.3 1.8
mVInput range = ±5 V –1.8 ±0.3 1.8
Offset error matching(channel-to-channel) All input ranges 0.5 5
mV
Offset error temperature drift All input ranges –3 ±0.3 3
ppm/°C
SAMPLING DYNAMICS
tACQ Acquisition time 1 µs
fSMaximum throughput rate per channelwithout latency All eight
channels included 200 kSPS
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Electrical Characteristics (continued)minimum and maximum
specifications are at TA = –40°C to +125°C, AVDD = 4.75 V to 5.25
V; typical specifications are at TA= 25°C; AVDD = 5 V, DVDD = 3 V,
VREF = 2.5 V (internal), and fSAMPLE = 200 kSPS (unless otherwise
noted)
PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
(5) Calculated on the first nine harmonics of the input
frequency.(6) Isolation crosstalk is measured by applying a
full-scale sinusoidal signal up to 160 kHz to a channel, not
selected in the multiplexing
sequence, and measuring the effect on the output of any selected
channel.(7) Does not include the variation in voltage resulting
from solder shift effects.(8) Recommended to use an X7R-grade,
0603-size ceramic capacitor for optimum performance (see the Layout
Guidelines section).
DYNAMIC CHARACTERISTICS
SNRSignal-to-noise ratio,no oversampling(VIN – 0.5 dBFS at 1
kHz)
Input range = ±10 V 92 94dB
Input range = ±5 V 90.25 93.2
SNROSRSignal-to-noise ratio,oversampling = 16x(VIN – 0.5 dBFS at
130 Hz)
Input range = ±10 V 99.6 101.8dB
Input range = ±5 V 97.4 99.2
THD Total harmonic distortion(5)
(VIN – 0.5 dBFS at 1 kHz)All input ranges –109.2 –95 dB
SINADSignal-to-noise + distortion ratio,no oversampling(VIN –
0.5 dBFS at 1 kHz)
Input range = ±10 V 91.75 93.9dB
Input range = ±5 V 90 93.1
SINADOSRSignal-to-noise + distortion ratio,oversampling =
16x(VIN – 0.5 dBFS at 130 Hz)
Input range = ±10 V 98.5 101dB
Input range = ±5 V 96.6 98.9
SFDR Spurious-free dynamic range(VIN – 0.5 dBFS at 1 kHz)All
input ranges 109 dB
Crosstalk isolation (6) –95 dB
BW(–3 dB) Small-signal bandwidth, –3 dB
At TA = 25°C,input range = ±10 V 24
kHzAt TA = 25°C,input range = ±5 V 16
BW(–0.1 dB) Small-signal bandwidth, –0.1 dB
At TA = 25°C,input range = ±10 V 14
kHzAt TA = 25°C,input range = ±5 V 9.5
tGROUP Group delayInput range = ±10 V 13
µsInput range = ±5 V 19
INTERNAL REFERENCE OUTPUT (REFSEL = 1)
VREF(7)Voltage on the REFIN/REFOUT pin(configured as output) At
TA = 25°C 2.4975 2.5 2.5025 V
Internal reference temperature drift 7.5 ppm/°C
C(REFIN_ REFOUT)Decoupling capacitor on theREFIN/REFOUT pin (8)
10 µF
V(REFCAP)Reference voltage to the ADC(on the REFCAPA, REFCAPB
pin) At TA = 25°C 3.996 4.0 4.004 V
Reference buffer output impedance 0.5 1 Ω
Reference buffer output temperature drift 5 ppm/°C
C(REFCAP)Decoupling capacitor on REFCAPA,REFCAPB 10 µF
Turn-on time C(REFCAP) = 10 µF,C(REFIN_REFOUT) = 10 µF25 ms
EXTERNAL REFERENCE INPUT (REFSEL = 0)
VREFIO_EXTExternal reference voltage on REFIO(configured as
input) 2.475 2.5 2.525 V
Reference input impedance 100 MΩ
Reference input capacitance 10 pF
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Incorporated
Electrical Characteristics (continued)minimum and maximum
specifications are at TA = –40°C to +125°C, AVDD = 4.75 V to 5.25
V; typical specifications are at TA= 25°C; AVDD = 5 V, DVDD = 3 V,
VREF = 2.5 V (internal), and fSAMPLE = 200 kSPS (unless otherwise
noted)
PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
POWER-SUPPLY REQUIREMENTS
AVDD Analog power-supply voltage Analog supply 4.75 5 5.25 V
DVDD Digital power-supply voltage Digital supply range 2.3 3.3
AVDD V
IAVDD_DYNAnalog supply current(operational)
AVDD = 5 V,fS = 200 kSPS,internal reference
17.7 24
mAAVDD = 5 V,fS = 200 kSPS,external reference
17.1 24
IAVDD_STCAnalog supply current(static)
AVDD = 5 V, internal reference,device not converting 12.4 17
mAAVDD = 5 V, external reference,device not converting 12 17
IAVDD_STDBYAVDD supplySTANDBY current
At AVDD = 5 V, device in STDBYmode, internal reference 4.2
5.5
mAAt AVDD = 5 V, device in STDBYmode, external reference 3.8
5.0
IAVDD_PWR_ DNAVDD supplypower-down current
At AVDD = 5 V, device in PWR_DN,internal orexternal reference,TA
= –40°C to +85°C
0.2 6 µA
IDVDD_DYN Digital supply currentDVDD = 3.3 V,fS = 200 kSPS
0.15 0.3 mA
IDVDD_STDBY DVDD supply STANDBY currentAt AVDD = 5 V, device in
STDBYmode 0.05 1.5 µA
IDVDD_PWR-DN DVDD supply power-down currentAt AVDD = 5 V, device
in PWR_DNmode 0.05 1.5 µA
DIGITAL INPUTS (CMOS)
VIH Digital high input voltage logic level DVDD > 2.3 V 0.7 ×
DVDD DVDD + 0.3 V
VIL Digital low input voltage logic level DVDD > 2.3 V –0.3
0.3 × DVDD V
Input leakage current 100 nA
Input pin capacitance 5 pF
DIGITAL OUTPUTS (CMOS)
VOH Digital high output voltage logic level IO = 100-µA source
0.8 × DVDD DVDD V
VOL Digital low output voltage logic level IO = 100-µA sink 0
0.2 × DVDD V
Floating state leakage current Only for SDO 1 µA
Internal pin capacitance 5 pF
TEMPERATURE RANGE
TA Operating free-air temperature –40 125 °C
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6.6 Timing Requirements: CONVST Controlminimum and maximum
specifications are at TA = –40°C to +125°C, typical specifications
are at TA = 25°C; AVDD = 5 V,2.3 V ≤ DVDD ≤ 5.25 V, VREF = 2.5 V
(internal), BUSY load = 20 pF, VIL and VIH at specified limits, and
fSAMPLE = 200 kSPS(unless otherwise noted) (see Figure 1)
MIN NOM MAX UNIT
tACQAcquisition time:BUSY falling edge to rising edge of
trailing CONVSTA or CONVSTB 1 µs
tPH_CN CONVSTA, CONVSTB pulse high time 25 nstPL_CN CONVSTA,
CONVSTB pulse low time 25 nstSU_BSYCS Setup time: BUSY falling to
CS falling 0 nstSU_RSTCN Setup time: RESET falling to first rising
edge of CONVSTA or CONVSTB 25 nstPH_RST RESET pulse high time 50
nstD_CNAB Delay between rising edges of CONVSTA and CONVSTB 500
µs
6.7 Timing Requirements: Data Read Operationminimum and maximum
specifications are at TA = –40°C to +125°C, typical specifications
are at TA = 25°C; AVDD = 5 V,2.3 V ≤ DVDD ≤ 5.25 V, VREF = 2.5 V
(internal), BUSY load = 20 pF, VIL and VIH at specified limits, and
fSAMPLE = 200 kSPS(unless otherwise noted) (see Figure 2)
MIN NOM MAX UNIT
tDZ_CNCSDelay between CONVSTA, CONVSTB rising edge to CS falling
edge, start ofdata read operation during conversion 10 ns
tDZ_CSBSYDelay between CS rising edge to BUSY falling edge, end
of data readoperation during conversion 40 ns
tSU_BSYCSSetup time: BUSY falling edge to CS falling edge, start
of data read operationafter conversion 0 ns
tD_CSCNDelay between CS rising edge to CONVSTA, CONVSTB rising
edge, end ofdata read operation after conversion 10 ns
6.8 Timing Requirements: Parallel Data Read Operation, CS and RD
Tied Togetherminimum and maximum specifications are at TA = –40°C
to +125°C, typical specifications are at TA = 25°C; AVDD = 5 V,2.3
V ≤ DVDD ≤ 5.25 V, VREF = 2.5 V (internal), load on DB[15:0] and
FRSTDATA = 20 pF, VIL and VIH at specified limits, andfSAMPLE = 200
kSPS (unless otherwise noted) (see Figure 3)
MIN NOM MAX UNITtPH_CS,tPH_RD
CS and RD high time 15 ns
tPL_CS,tPL_RD
CS and RD low time 15 ns
tHT_RDDB,tHT_CSDB
Hold time: RD and CS rising edge to DB[15:0] invalid 2.5 ns
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6.9 Timing Requirements: Parallel Data Read Operation, CS and RD
Separateminimum and maximum specifications are at TA = –40°C to
+125°C, typical specifications are at TA = 25°C; AVDD = 5 V,2.3 V ≤
DVDD ≤ 5.25 V, VREF = 2.5 V (internal), load on DB[15:0] and
FRSTDATA = 20 pF, VIL and VIH at specified limits, andfSAMPLE = 200
kSPS (unless otherwise noted) (see Figure 4)
MIN NOM MAX UNITtSU_CSRD Set-up time: CS falling edge to RD
falling edge 0 nstHT_RDCS Hold time: RD rising edge to CS rising
edge 0 nstPL_RD RD low time 15 nstPH_RD RD high time 15 nstHT_CSDB
Hold time: CS rising edge to DB[15:0] becoming invalid 6 nstHT_RDDB
Hold time: RD rising edge to DB[15:0] becoming invalid 2.5 ns
6.10 Timing Requirements: Serial Data Read Operationminimum and
maximum specifications are at TA = –40°C to +125°C, typical
specifications are at TA = 25°C; AVDD = 5 V,2.3 V ≤ DVDD ≤ 5.25 V,
VREF = 2.5 V (internal), load on DOUTA, DOUTB, and FRSTDATA = 20
pF, VIL and VIH at specifiedlimits, and fSAMPLE = 200 kSPS (unless
otherwise noted) (see Figure 5)
MIN NOM MAX UNITtSCLK SCLK time period 50 nstPH_SCLK SCLK high
time 0.45 0.55 tSCLKtPL_SCLK SCLK low time 0.45 0.55 tSCLKtHT_CKDO
Hold time: SCLK rising edge to DOUTA, DOUTB invalid 7 nstSU_CSCK
Setup time: CS falling to first SCLK edge 8 nstHT_CKCS Hold time:
last SCLK active edge to CS high 10 ns
6.11 Timing Requirements: Byte Mode Data Read Operationminimum
and maximum specifications are at TA = –40°C to +125°C, typical
specifications are at TA = 25°C; AVDD = 5 V,2.3 V ≤ DVDD ≤ 5.25 V,
VREF = 2.5 V (internal), load on DB[7:0] and FRSTDATA = 20 pF, VIL
and VIH at specified limits, andfSAMPLE = 200 kSPS (unless
otherwise noted) (see Figure 6)
MIN NOM MAX UNITtSU_CSRD Setup time: CS falling edge to RD
falling edge 0 nstHT_RDCS Hold time: RD rising edge to CS rising
edge 0 nstPL_RD RD low time 15 nstPH_RD RD high time 15 nstHT_CSDB
Hold time: CS rising edge to DB[15:0] becoming invalid 6 nstHT_RDDB
Hold time: RD rising edge to DB[15:0] becoming invalid 2.5 ns
6.12 Timing Requirements: Oversampling Modeminimum and maximum
specifications are at TA = –40°C to +125°C, typical specifications
are at TA = 25°C; AVDD = 5 V,2.3 V ≤ DVDD ≤ 5.25 V, VREF = 2.5 V
(internal), VIL and VIH at specified limits, and fSAMPLE = 200 kSPS
(unless otherwisenoted) (see Figure 7)
MIN NOM MAX UNITtHT_OS Hold time: BUSY falling to OSx 20
nstSU_OS Setup time: BUSY falling to OSx 20 ns
(1) First conversion data must be discarded or RESET must be
issued if the maximum timing is exceeded.
6.13 Timing Requirements: Exit Standby Modeminimum and maximum
specifications are at TA = –40°C to +125°C, typical specifications
are at TA = 25°C, AVDD = 5 V,2.3 V ≤ DVDD ≤ 5.25 V, VREF = 2.5 V
(internal), VIL and VIH at specified limits, and fSAMPLE = 200 kSPS
(unless otherwisenoted) (see Figure 8)
MIN NOM MAX UNITtD_STBYCN Delay between STBY rising edge to
CONVSTA or CONVSTB rising edge (1) 100 µs
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(1) Excludes wake-up time for external reference device.
6.14 Timing Requirements: Exit Shutdown Modeminimum and maximum
specifications are at TA = –40°C to +125°C, typical specifications
are at TA = 25°C; AVDD = 5 V,2.3 V ≤ DVDD ≤ 5.25 V, VREF = 2.5 V
(internal), VIL and VIH at specified limits, and fSAMPLE = 200 kSPS
(unless otherwisenoted) (see Figure 9)
MIN NOM MAX UNIT
tD_SDRST Delay between STBY rising edge to RESET rising
edgeInternal reference mode 50
msExternal reference mode (1) 13
tPH_RST RESET high time 50 nstD_RSTCN Delay between RESET
falling edge to CONVSTA or CONVSTB rising edge 25 µs
6.15 Switching Characteristics: CONVST Controlminimum and
maximum specifications are at TA = –40°C to +125°C, typical
specifications are at TA = 25°C; AVDD = 5 V,2.3 V ≤ DVDD ≤ 5.25 V,
VREF = 2.5 V (internal), BUSY load = 20 pF, VIL and VIH at
specified limits, and fSAMPLE = 200 kSPS(unless otherwise noted)
(see Figure 1)
PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
tCYC ADC cycle time period
No oversampling, parallel read, serialread with both DOUTA and
DOUTBduring conversion
5
µsNo oversampling, serial read afterconversion with both DOUTA
andDOUTB
9.7
No oversampling, serial read afterconversion with only DOUTA
orDOUTB
15
tCONV Conversion time: BUSY high time
No oversampling 3.7 3.8 3.9
µs
Oversampling by 2 8.4 8.8Oversampling by 4 17 18Oversampling by
8 34 36Oversampling by 16 68 72Oversampling by 32 136
144Oversampling by 64 272 288
tD_CNBSYDelay between trailing rising edges ofCONVSTA or CONVSTB
and BUSYrising
15 ns
6.16 Switching Characteristics: Parallel Data Read Operation, CS
and RD Tied Togetherminimum and maximum specifications are at TA =
–40°C to +125°C, typical specifications are at TA = 25°C; AVDD = 5
V,2.3 V ≤ DVDD ≤ 5.25 V, VREF = 2.5 V (internal), load on DB[15:0]
and FRSTDATA = 20 pF, VIL and VIH at specified limits, andfSAMPLE =
200 kSPS (unless otherwise noted) (see Figure 3)
PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
tD_CSDB,tD_RDDB
Delay time: CS and RD falling edge toDB[15:0] becoming valid(out
of tri-state)
12 ns
tD_CSFD,tD_RDFD
Delay time: CS and RD falling edge toFRSTDATA going high or low
out of tri-state
10 ns
tDHZ_CSDB,tDHZ_RDDB
Delay time: CS and RD rising edge toDB[15:0] tri-state 12 ns
tDHZ_CSFD,tDHZ_RDFD
Delay time: CS and RD rising edge toFRSTDATA tri-state 10 ns
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6.17 Switching Characteristics: Parallel Data Read Operation, CS
and RD Separateminimum and maximum specifications are at TA = –40°C
to +125°C, typical specifications are at TA = 25°C; AVDD = 5 V,2.3
V ≤ DVDD ≤ 5.25 V, VREF = 2.5 V (internal), load on DB[15:0] and
FRSTDATA = 20 pF, VIL and VIH at specified limits, andfSAMPLE = 200
kSPS (unless otherwise noted) (see Figure 4)
PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
tD_CSDBDelay time: CS falling edge to DB[15:0]becoming valid(out
of tri-state)
12 ns
tD_RDDBDelay time: RD falling edge to new dataon DB[15:0] 17
ns
tDHZ_CSDBDelay time: CS rising edge to DB[15:0]becoming
tri-state 12 ns
tD_CSFDDelay time: CS falling edge toFRSTDATA going low out of
tri-state 15 ns
tDHZ_CSFDDelay time: CS rising edge toFRSTDATA going to
tri-state 10 ns
tD_RDFDDelay time: RD falling edge toFRSTDATA going high or low
15 ns
6.18 Switching Characteristics: Serial Data Read
Operationminimum and maximum specifications are at TA = –40°C to
+125°C, typical specifications are at TA = 25°C; AVDD = 5 V,2.3 V ≤
DVDD ≤ 5.25 V, VREF = 2.5 V (internal), load on DOUTA, DOUTB, and
FRSTDATA = 20 pF, VIL and VIH at specifiedlimits, and fSAMPLE = 200
kSPS (unless otherwise noted) (see Figure 5)
PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
tD_CSDODelay time: CS falling edge to DOUTA,DOUTB enable(out of
tri-state)
12 ns
tD_CKDODelay time: SCLK rising edge to validdata on DOUTA, DOUTB
15 ns
tDZ_CSDODelay time: CS rising edge to DOUTA,DOUTB going to
tri-state 12 ns
tD_CSFDDelay time: CS falling edge toFRSTDATA from tri-state to
high or low 10 ns
tDZ_CKFDDelay time: 18th SCLK falling edge toFRSTDATA falling
edge 15 ns
tDHZ_CSFDDelay time: CS rising edge toFRSTDATA going to
tri-state 10 ns
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CONVSTA
CONVSTB
BUSY tCONV
tD_CNAB
tD_CNBSY
tACQ
tCYC
tPH_CNtPL_CN
CS
tSU_BSYCS
RESET
tSU_RSTCN
tPH_RST
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6.19 Switching Characteristics: Byte Mode Data Read
Operationminimum and maximum specifications are at TA = –40°C to
+125°C, typical specifications are at TA = 25°C; AVDD = 5 V,2.3 V ≤
DVDD ≤ 5.25 V, VREF = 2.5 V (internal), load on DB[7:0] and
FRSTDATA = 20 pF, VIL and VIH at specified limits, andfSAMPLE = 200
kSPS (unless otherwise noted) (see Figure 6)
PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
tD_CSDBDelay time: CS falling edge toDB[7:0] becoming valid(out
of tri-state)
12 ns
tD_RDDBDelay time: RD falling edge tonew data on DB[7:0] 17
ns
tDHZ_CSDB
Delay time: CS rising edge toDB[7:0] becoming tri-state 12
ns
tD_CSFDDelay time: CS falling edge toFRSTDATA going low out of
tri-state
10 ns
tD_RDFDDelay time: RD falling edge toFRSTDATA going low or
highstate
15 ns
tDHZ_CSFDDelay time: CS rising edge toFRSTDATA going to
tri-state 10 ns
Figure 1. CONVST Control Timing Diagram
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CS
DB[15:0]
FRSTDATA
RD
tD_CSDB
tD_CSFD
AIN_1[17:2]
AIN_1[1:0]
AIN_2[17:2]
AIN_2[1:0]
AIN_3[17:2]
AIN_8[17:2]
AIN_8[1:0]
tPH_RD
tHT_CSDBtDHZ_CSDB
tDHZ_CSFD
tSU_CSRDtPL_RD
Invalid
tHT_RDDBtD_RDDB
tHT_RDCS
tD_RDFD
DB[15:0]
FRSTDATA
tD_CSDB
tD_CSFD
AIN_1[17:2]
AIN_1[1:0]
tPH_RD
tDHZ_CSDB
tDHZ_CSFD
AIN_2[17:2]
AIN_2[1:0]
AIN_7[17:2]
AIN_7[1:0]
AIN_8[17:2]
AIN_8[1:0]
tD_RDDB
tPH_CS
tD_RDFD
tDHZ_RDDB
tDHZ_RDFD
tPL_RDtPL_CS
tHT_RDDBtHT_CSDB
CS RD,
CONVSTACONVSTB
BUSY
tDZ_CNCS
CS
tDZ_CSBSY
tSU_BSYCS tD_CSCN
Read During Conversion Read After Conversion
RESET tPH_RST
tSU_RSTCN
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Figure 2. Data Read Operation Timing Diagram
Figure 3. Parallel Data Read Operation, CS and RD Tied
Together
Figure 4. Parallel Data Read Operation, CS and RD Separate
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CONVSTACONVSTB
BUSY
OSR x
OSR latched for Conversion (N+1)
tHT_OS
Conversion N
Conversion N+1
tSU_OS
CS
DB[7:0]
FRSTDATA
RDtD_CSDB
tD_CSFD
High Byte AIN_1
Mid Byte AIN_1
Low Byte AIN_1
High Byte AIN_2
Mid Byte AIN_8
Low Byte AIN_8
tPH_RD
tHT_CSDBtDHZ_CSDB
tDHZ_CSFD
tSU_CSRDtPL_RD
Invalid
tD_RDFD
tHT_RDDB tD_RDDB
tHT_RDCS
FRSTDATA
tDHZ_CSFD
CS
SCLK
DB17 DB16 DB15 DB1 DB0DOUTADOUTB
tPH_SCLKtPL_SCLK
tSCLK
tSU_CSCK
tD_CSDOtHT_CKDO tD_CKDO
tDZ_CKFD
tDZ_CSDO
tHT_CKCS
tD_CSFD
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Figure 5. Serial Data Read Operation Timing Diagram
Figure 6. Byte Mode Data Read Operation Timing Diagram
Figure 7. Oversampling Mode Timing Diagram
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STBY
tD_SDRST
RANGE
RESET
CONVSTACONVSTB
tPH_RST
tD_RSTCN
STBY
tD_STBYCN
RANGE
CONVSTACONVSTB
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Figure 8. Exit Standby Mode Timing Diagram
Figure 9. Exit Shutdown Mode Timing Diagram
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Output Codes
Num
ber
of H
its
0
100
200
300
400
500
600
700
800
-6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10 11
D010Codes (LSB) 2's Complement
Diff
eren
tial N
onlin
earit
y (L
SB
)
-131072 -65536 0 65536 131071-1.5
-1
-0.5
0
0.5
1
1.5
D011
Free-Air Temperature (qC)
Inpu
t Im
peda
nce
(M:
)
-40 -7 26 59 92 1250.95
0.97
0.99
1.01
1.03
1.05
D004
± 10 V± 5 V
Output Codes
Num
ber
of H
its
0
100
200
300
400
500
600
700
-9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10
D009
Input Voltage (V)
Ana
log
Inpu
t Cur
rent
(uA
)
-10 -6 -2 2 6 10-15
-9
-3
3
9
15
D002
25 C-40 C125 C
Input Voltage (V)
Ana
log
Inpu
t Cur
rent
(uA
)
-5 -3 -1 1 3 5-9
-6
-3
0
3
6
9
D003
25 C-40 C125 C
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6.20 Typical Characteristicsat TA = 25°C, AVDD = 5 V, DVDD = 3
V, internal reference VREF = 2.5 V, and fS = 200 kSPS per channel
(unless otherwisenoted)
Figure 10. Analog Input Current vs Input Voltage andTemperature
(±10 V)
Figure 11. Analog Input Current vs Input Voltage andTemperature
(±5 V)
Figure 12. Input Impedance vs Free-Air Temperature
Mean = 0.71, sigma = 1.83, number of hits = 4096, VIN = 0 V
Figure 13. DC Histogram of Codes (±10 V)
Mean = 0.86, sigma = 2.1, number of hits = 4096, VIN = 0 V
Figure 14. DC Histogram of Codes (±5 V) Figure 15. DNL for All
Codes
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Free-Air Temperature (qC)
Inte
gral
Non
linea
rity
(LS
B)
-40 -7 26 59 92 125-10
-6
-2
2
6
10
D016
MaximumMinimum
Free-Air Temperature (qC)
Offs
et E
rror
(m
V)
-40 -7 26 59 92 125-1.8
-1.08
-0.36
0.36
1.08
1.8
D017
± 10 V± 5 V
Codes (LSB) 2's Complement
Inte
gral
Non
linea
rity
(LS
B)
-131072 -65536 0 65536 131071-5
-3
-1
1
3
5
D014 Free-Air Temperature (qC)
Inte
gral
Non
linea
rity
(LS
B)
-40 -7 26 59 92 125-10
-6
-2
2
6
10
D015
MaximumMinimum
Free-Air Temperature (qC)
Diff
eren
tial N
onlin
earit
y (L
SB
)
-40 -7 26 59 92 125-1.5
-0.75
0
0.75
1.5
D012
MaximumMinimum
Codes (LSB) 2's Complement
Inte
gral
Non
linea
rity
(LS
B)
-131072 -65536 0 65536 131071-5
-3
-1
1
3
5
D013
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Typical Characteristics (continued)at TA = 25°C, AVDD = 5 V,
DVDD = 3 V, internal reference VREF = 2.5 V, and fS = 200 kSPS per
channel (unless otherwisenoted)
Figure 16. DNL vs Free-Air Temperature Figure 17. INL vs All
Codes (±10 V)
Figure 18. INL vs All Codes (±5 V) Figure 19. INL vs Free-Air
Temperature (±10 V)
Figure 20. INL vs Free-Air Temperature (±5 V) Figure 21. Offset
Error vs Free-Air Temperature
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Free-Air Temperature (qC)
Gai
n E
rror
(LS
B)
-40 -7 26 59 92 125-200
-100
0
100
200
D022
± 10 V± 5 V
Gain Drift (ppm/qC)
Num
ber
of H
its
0
10
20
30
40
50
60
70
80
0 1.76 4.21 5.595 6.98 8.365 9.75 11.13512.52 14
D023
Free-Air Temperature (qC)
Offs
et E
rror
(m
V)
-40 -7 26 59 92 125-1.8
-1.08
-0.36
0.36
1.08
1.8
D021
Channel 1Channel 2Channel 3
Channel 4Channel 5Channel 6
Channel 7Channel 8
Offset Drift (ppm/qC)
Num
ber
of H
its
0
10
20
30
40
50
60
70
80
90
100
110
120
130
0 0.22 0.49 0.76 1.03 1.3 1.57 1.84 2.11 2.38 2.65 3
D020
Free-Air Temperature (qC)
Offs
et E
rror
(m
V)
-40 -7 26 59 92 125-1.8
-1.08
-0.36
0.36
1.08
1.8
D019
Channel 1Channel 2Channel 3
Channel 4Channel 5Channel 6
Channel 7Channel 8
Offset Drift (ppm/qC)
Num
ber
of H
its
0
10
20
30
40
50
60
70
80
90
100
110
120
130
0 0.355 0.76 1.165 1.57 1.975 2.38 2.785 3
D018
20
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Typical Characteristics (continued)at TA = 25°C, AVDD = 5 V,
DVDD = 3 V, internal reference VREF = 2.5 V, and fS = 200 kSPS per
channel (unless otherwisenoted)
Figure 22. Offset Drift Histogram Distribution (±10 V) Figure
23. Offset Error Across Channels vs Free-AirTemperature (±10 V)
Figure 24. Offset Drift Histogram Distribution (±5 V) Figure 25.
Offset Error Across Channels vs Free-AirTemperature (±5 V)
External reference
Figure 26. Gain Error vs Temperature
External reference
Figure 27. Gain Error Drift Histogram Distribution (±10 V)
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-
Frequency (kHz)
Am
plitu
de (
dB)
0 25 50 75 100-200
-150
-100
-50
0
D028Frequency (kHz)
Am
plitu
de (
dB)
0 25 50 75 100-200
-150
-100
-50
0
D029
Free-Air Temperature (qC)
Gai
n E
rror
(LS
B)
-40 -7 26 59 92 125-250
-150
-50
50
150
250
D026
Channel 1Channel 2Channel 3Channel 4Channel 5Channel 6Channel
7Channel 8
Source Resistance (k:)
Gai
n E
rror
(%
FS
)
0 50 100 150 200-20
0
20
40
60
80
100
D027
± 10 V± 5 V
Free-Air Temperature (qC)
Gai
n E
rror
(LS
B)
-40 -7 26 59 92 125-500
-350
-200
-50
100
250
400
D024
Channel 1Channel 2Channel 3Channel 4Channel 5Channel 6Channel
7Channel 8
Gain Drift (ppm/qC)
Num
ber
of H
its
0
10
20
30
40
50
60
70
80
0 1.76 4.21 5.595 6.98 8.365 9.75 11.13512.52 14
D025
21
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Incorporated
Typical Characteristics (continued)at TA = 25°C, AVDD = 5 V,
DVDD = 3 V, internal reference VREF = 2.5 V, and fS = 200 kSPS per
channel (unless otherwisenoted)
External reference
Figure 28. Gain Error Across Channels vs Free-AirTemperature
(±10 V)
External reference
Figure 29. Gain Error Drift Histogram Distribution (±5 V)
External reference
Figure 30. Gain Error Across Channels vs Free-AirTemperature (±5
V)
Figure 31. Gain Error as a Function of External
SourceResistance
Number of points = 256k, SNR = 93.77 dB,SINAD = 93.52 dB, THD =
–105.93, SFDR = 106.98 dB
Figure 32. Typical FFT Plot (±10 V)
Number of points = 256k, SNR = 92.45 dB,SINAD = 92.26 dB, THD =
–105.85 dB, SFDR = 107.12 dB
Figure 33. Typical FFT Plot (±5 V)
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-
Input Frequency (Hz)
Sig
nal-t
o-N
oise
Rat
io (
dB)
85
89
93
97
101
105
10 100 1k 10k 100k
D034
OSR-0OSR-2OSR-4OSR-8
OSR-16OSR-32OSR-64
Input Frequency (Hz)
Sig
nal-t
o-N
oise
Rat
io (
dB)
88
91
94
97
100
103
10 100 1k 10k 100k
D035
OSR-0OSR-2OSR-4OSR-8OSR-16OSR-32OSR-64
Input Frequency (Hz)
Sig
nal-t
o-N
oise
Rat
io (
dB)
89
90
91
92
93
94
95
100 1k 10k 100k
D032
± 10 V± 5 V
Free-Air Temperature q(C)
Sig
nal-t
o-N
oise
Rat
io (
dB)
-40 -7 26 59 92 12590
91
92
93
94
95
D033
± 10 V± 5 V
Frequency (kHz)
Am
plitu
de (
dB)
0 1.25 2.5 3.75 5 6.25-200
-150
-100
-50
0
D030Frequency (kHz)
Am
plitu
de (
dB)
0 1.25 2.5 3.75 5 6.25-200
-150
-100
-50
0
D031
22
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Typical Characteristics (continued)at TA = 25°C, AVDD = 5 V,
DVDD = 3 V, internal reference VREF = 2.5 V, and fS = 200 kSPS per
channel (unless otherwisenoted)
Number of points = 256k, SNR = 100.48 dB,SINAD = 99.9 dB, THD =
–105.93 dB, SFDR = 106.21 dB
Figure 34. Typical FFT Plot for OSR 16x (±10 V)
Number of points = 256k, SNR = 99.26 dB,SINAD = 98.63 dB, THD =
–105.84 dB, SFDR = 105.94 dB
Figure 35. Typical FFT Plot for OSR 16x (±5 V)
OSR = 0
Figure 36. SNR vs Input Frequency for Different InputRanges
OSR = 0
Figure 37. SNR vs Free-Air Temperature for Different
InputRanges
Figure 38. SNR vs Input Frequency for Different OSR(±10 V)
Figure 39. SNR vs Input Frequency for Different OSR(±5 V)
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-
Input Frequency (Hz)
Tot
al H
arm
onic
Dis
tort
ion
(dB
)
-120
-110
-100
-90
-80
-70
-60
1k 10k 100k
D040
0 k:10 k:20 k:30 k:40 k:50 k:61 k:68.1 k:82.5 k:90.9 k:100
k:
Input Frequency (Hz)
Tot
al H
arm
onic
Dis
tort
ion
(dB
)
-120
-110
-100
-90
-80
-70
-60
1k 10k 100k
D041
0 k:10 k:20 k:30 k:40 k:50 k:61 k:68.1 k:82.5 k:90.9 k:100
k:
Input Frequency (Hz)
Tot
al H
arm
onic
Dis
tort
ion
(dB
)
-130
-125
-120
-115
-110
-105
-100
-95
-90
-85
-80
100 1k 10k 100k
D038
± 10 V± 5 V
Free-Air Temperature (qC)
Tot
al H
arm
onic
Dis
tort
ion
(dB
)
-40 -7 26 59 92 125-120
-115
-110
-105
-100
D039
± 10 V± 5 V
Input Frequency (Hz)
Sig
nal-t
o-N
oise
+ D
isto
rtio
n R
atio
(dB
)
89
90
91
92
93
94
95
100 1k 10k 100k
D036
± 10 V± 5 V
Free-Air Temperature (qC)
Sig
nal-t
o-N
oise
+ D
isto
rtio
n R
atio
(dB
)
-40 -7 26 59 92 12590
91
92
93
94
95
D037
± 10 V± 5 V
23
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Incorporated
Typical Characteristics (continued)at TA = 25°C, AVDD = 5 V,
DVDD = 3 V, internal reference VREF = 2.5 V, and fS = 200 kSPS per
channel (unless otherwisenoted)
OSR = 0
Figure 40. SINAD vs Input Frequency for Different
InputRanges
OSR = 0
Figure 41. SINAD vs Free-Air Temperature for Different
InputRanges
Figure 42. THD vs Input Frequency for Different InputRanges
Figure 43. THD vs Free-Air Temperature for Different
InputRanges
Figure 44. THD vs Input Frequency for Different SourceImpedances
(±10 V)
Figure 45. THD vs Input Frequency for Different SourceImpedances
(±5 V)
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-
Free-Air Temperature (qC)
Ana
log
Sup
ply
Cur
rent
(P
A)
-40 -7 26 59 92 125-1
0
1
2
3
4
5
6
D057Free-Air Temperature (qC)
Ana
log
Sup
ply
Cur
rent
(m
A)
-40 -7 26 59 92 1254.12
4.14
4.16
4.18
4.2
4.22
4.24
4.26
D056
Free-Air Temperature (qC)
Ana
log
Sup
ply
Cur
rent
(m
A)
-40 -7 26 59 92 12516.5
17
17.5
18
18.5
19
19.5
D053
± 10 V± 5 V
Free-Air Temperature (qC)
Ana
log
Sup
ply
Cur
rent
(m
A)
-40 -7 26 59 92 12512.2
12.4
12.6
12.8
13
13.2
13.4
13.6
D055
± 10 V± 5 V
Frequency (kHz)
Isol
atio
n C
ross
talk
(dB
)
-140
-130
-120
-110
-100
-90
100m 1 10 100
D042
±5 V±10 V
Frequency (kHz)
Isol
atio
n C
ross
talk
(dB
)
-150
-140
-130
-120
-110
-100
-90
100m 1 10 100D043
± 5 V± 10 V
24
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Typical Characteristics (continued)at TA = 25°C, AVDD = 5 V,
DVDD = 3 V, internal reference VREF = 2.5 V, and fS = 200 kSPS per
channel (unless otherwisenoted)
Figure 46. Isolation Crosstalk vs Frequency(Inputs Within
Range)
Figure 47. Isolation Crosstalk vs Frequency
(SaturatedInputs)
Figure 48. Analog Supply Current (Operational) vs
Free-AirTemperature
Figure 49. Analog Supply Current (Static) vs Free-AirTemperature
(Sampling)
Figure 50. Analog Supply Current vs Free-Air
Temperature(Standby)
Figure 51. Analog Supply Current vs Free-Air
Temperature(Shutdown)
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-
18-bitSAR ADC
2.5 V VREF
REFGNDAGND
DVDDAVDD
ADS8598S
ADCDriver
REFIN / REFOUT
REFCAPB
REFSEL
Digital Filter OS1
OS0
OS2
SARLogic and
Digital Control DB[15:0]
DOUTA
DOUTB
RANGE
CS
RESET
CONVSTA/B
FRSTDATA
REFCAPA
BUSY1 M�
Clamp3rd -Order
LPFClampPGA
ADCDriver
Clamp
ClampPGA
ADCDriver
Clamp
ClampPGA
Clamp
ClampPGA
Clamp
ClampPGA
Clamp
ClampPGA
Clamp
ClampPGA
Clamp
ClampPGA
AIN_1P
AIN_1GND
AIN_2P
AIN_2GND
AIN_3P
AIN_3GND
AIN_4P
AIN_4GND
AIN_5P
AIN_5GND
AIN_6P
AIN_6GND
AIN_7P
AIN_7GND
AIN_8P
AIN_8GND
PAR/ SER
RD/SCLK
STBY
SER / PARInterface
ADCDriver
ADCDriver
ADCDriver
ADCDriver
ADCDriver
18-bitSAR ADC
18-bitSAR ADC
18-bitSAR ADC
18-bitSAR ADC
18-bitSAR ADC
18-bitSAR ADC
18-bitSAR ADC
1 M�
1 M�
1 M�
1 M�
1 M�
1 M�
1 M�
1 M�
1 M�
1 M�
1 M�
1 M�
1 M�
1 M�
1 M�
Copyright © 2017, Texas Instruments Incorporated
3rd -OrderLPF
3rd -OrderLPF
3rd -OrderLPF
3rd -OrderLPF
3rd -OrderLPF
3rd -OrderLPF
3rd -OrderLPF
25
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Incorporated
7 Detailed Description
7.1 OverviewThe ADS8598S is an 18-bit data acquisition (DAQ)
system with 8-channel analog inputs. Each analog inputchannel
consists of an input clamp protection circuit, a programmable gain
amplifier (PGA), a third-order, low-pass filter, and a
track-and-hold circuit that facilitates simultaneous sampling of
the signals on all input channels.The sampled signal is digitized
using an 18-bit analog-to-digital converter (ADC), based on the
successiveapproximation register (SAR) architecture. This overall
system can achieve a maximum throughput of 200 kSPSfor each
channel. The device features a 2.5-V internal reference with a
fast-settling buffer, a programmabledigital averaging filter to
improve noise performance, and high speed serial and parallel
interfaces forcommunication with a wide variety of digital
hosts.
The device operates from a single 5-V analog supply and can
accommodate true bipolar input signals of ±10 Vand ±5 V. The input
clamp protection circuitry can tolerate voltages up to ±15 V. The
device offers a constant1-MΩ resistive input impedance irrespective
of the sampling frequency or the selected input range.
Theintegration of multiple, simultaneously sampling precision ADC
inputs and analog front-end circuits with highinput impedance
operating from a single 5-V supply offers a simplified end solution
without requiring externalhigh-voltage bipolar supplies and
complicated driver circuits.
7.2 Functional Block Diagram
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-
AIN_nP
AIN_nGNDADCDriver
1 M:Clamp
1 M:
ClampPGA
18-bitSARADC
3rd-OrderLPF
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7.3 Feature Description
7.3.1 Analog InputsThe ADS8598S has 8 analog input channels,
such that the positive inputs AIN_nP (n = 1 to 8) are the
single-ended analog inputs and the negative inputs AIN_nGND are
tied to GND. Figure 52 shows the simplified circuitschematic for
each analog input channel, including the input clamp protection
circuit, PGA, low-pass filter, high-speed ADC driver, and a
precision 18-bit SAR ADC.
Figure 52. Front-End Circuit Schematic for Each Analog Input
Channel
The device can support two bipolar, single-ended input voltage
ranges based on the logic level of the RANGEinput pin. As explained
in the RANGE (Input) section, the input voltage range for all
analog channels can beconfigured to bipolar ±10 V or ±5 V. The
device samples the voltage difference (AIN_nP – AIN_nGND)
betweenthe selected analog input channel and the AIN_nGND pin. The
device allows a ±0.3-V range on the AIN_nGNDpin for all analog
input channels. Use this feature in modular systems where the
sensor or signal conditioningblock is further away from the ADC on
the board and when a difference in the ground potential of the
sensor orsignal conditioner from the ADC ground is possible. In
such cases, running separate wires from the AIN_nGNDpin of the
device to the sensor or signal conditioning ground is
recommended.
7.3.2 Analog Input ImpedanceEach analog input channel in the
device presents a constant resistive impedance of 1 MΩ. The input
impedancefor each channel is independent of either the input signal
frequency, the configured range of the ADC, or theoversampling
mode. The primary advantage of such high-impedance inputs is the
ease of driving the ADC inputswithout requiring driving amplifiers
with low output impedance. Bipolar, high-voltage power supplies are
notrequired in the system because this ADC does not require any
high-voltage, front-end drivers. In mostapplications, the signal
sources or sensor outputs can be directly connected to the ADC
input, thus significantlysimplifying the design of the signal
chain.
In order to maintain the dc accuracy of the system, matching the
external source impedance on the AIN_nP inputpin with an equivalent
resistance on the AIN_nGND pin is recommended (see Figure 54). This
matching helps tocancel any additional offset error contributed by
the external resistance.
7.3.3 Input Clamp Protection CircuitAs illustrated in Figure 52,
the ADS8598S features an internal clamp protection circuit on each
of the 8 analoginput channels. Use of external protection circuits
is recommended as a secondary protection scheme to protectthe
device. Using external protection devices helps with protection
against surges, electrostatic discharge (ESD),and electrical fast
transient (EFT) conditions.
The input clamp protection circuit on the ADS8598S allows each
analog input to swing up to a maximum voltageof ±15 V. Beyond an
input voltage of ±15 V, the input clamp circuit turns on, still
operating off the single 5-Vsupply. Figure 53 illustrates a typical
current versus voltage characteristic curve for the input clamp.
There is nocurrent flow in the clamp circuit for input voltages up
to ±15 V. Beyond this voltage, the input clamp circuit turnson.
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-
REXTAIN_nP
AIN_nGNDREXT
Input Signal
C
1 M
Clamp
1 M
Clamp
PGA
Input Voltage (V)
Inpu
t Cla
mp
Cur
rent
(m
A)
-20 -15 -10 -5 0 5 10 15 20-50
-40
-30
-20
-10
0
10
20
30
40
50
D007
27
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Incorporated
Feature Description (continued)
Figure 53. I-V Curve for an Input Clamp Protection Circuit (AVDD
= 5 V)
For input voltages above the clamp threshold, make sure that
input current never exceeds the absolutemaximum rating (see the
Absolute Maximum Ratings table) of ±10 mA to prevent any damage to
the device.Figure 54 shows that a small series resistor placed in
series with the analog inputs is an effective way to limit theinput
current. In addition to limiting the input current, this resistor
can also provide an antialiasing, low-pass filterwhen coupled with
a capacitor. In order to maintain the dc accuracy of the system,
matching the external sourceimpedance on the AIN_nP input pin with
an equivalent resistance on the AIN_nGND pin is recommended.
Thismatching helps to cancel any additional offset error
contributed by the external resistance.
Figure 54. Matching Input Resistors on the Analog Inputs of
Device
The input overvoltage protection clamp on the ADS8598S is
intended to control transient excursions on the inputpins. Leaving
the device in a state such that the clamp circuit is activated for
extended periods of time in normalor power-down mode is not
recommended because this fault condition can degrade device
performance andreliability.
7.3.4 Programmable Gain Amplifier (PGA)The device offers a
programmable gain amplifier (PGA) at each individual analog input
channel that converts theoriginal single-ended input signal into a
fully-differential signal to drive the internal 18-bit SAR ADC. The
PGAalso adjusts the common-mode level of the input signal before
being fed into the ADC to ensure maximum usageof the ADC input
dynamic range. Depending on the range of the input signal, the PGA
gain can be accordinglyadjusted by configuring the RANGE pin of the
ADC (see the RANGE (Input) section).
The PGA uses a very highly matched network of resistors for
programmable gain configurations. Matchingbetween these resistors
and the amplifiers across all channels is accurately trimmed to
keep the overall gainerror low across all channels and input
ranges.
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-
Input Frequency (Hz)
Mag
nitu
de (
dB)
-10
-8
-6
-4
-2
0
100 1k 10k 100k
D046
± 5 V± 10 V
Input Frequency (Hz)G
roup
Del
ay (P
s)0
5
10
15
20
25
30
1 10 100 1k 10k 100k
D047
± 5 V± 10 V
28
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Feature Description (continued)7.3.5 Third-Order, Low-Pass
Filter (LPF)In order to mitigate the noise of the front-end
amplifiers and gain resistors of the PGA, each analog input
channelof the ADS8598S features a third-order, Butterworth
antialiasing, low-pass filter (LPF) at the output of the PGA.Figure
55 and Figure 56 (respectively) show the magnitude and phase
response of the analog antialiasing filter.For maximum performance,
the –3-dB cutoff frequency for the antialiasing filter is designed
to be equal to 24 kHzfor the ±10-V range and 16 kHz for the ±5-V
range.
Figure 55. Third-Order LPF Magnitude Response Figure 56.
Third-Order LPF Phase Response
7.3.6 ADC DriverIn order to meet the performance of an 18-bit,
SAR ADC at the maximum sampling rate (200 kSPS per channel),the
capacitors at the input of the ADC must be successfully charged and
discharged during the acquisition timewindow. The inputs of the ADC
must settle to better than 18-bit accuracy before any sampled
analog voltagegets converted. This drive requirement at the inputs
of the ADC necessitates the use of a high-bandwidth, low-noise, and
stable amplifier buffer. The ADS8598S features an integrated input
driver as part of the signal chainfor each analog input. This
integrated input driver eliminates the need for any external
amplifier, thus simplifyingthe signal chain design.
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-
29
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Incorporated
Feature Description (continued)7.3.7 Digital Filter and NoiseThe
ADS8598S features an optional digital averaging filter that can be
used in slower throughput applicationsrequiring lower noise and
higher dynamic range. As explained in Table 1, the oversampling
ratio of the digitalfilter is determined by the configuration of
the OS[2:0] pins. The overall throughput of the ADC
decreasesproportionally with increase in the oversampling
ratio.
Table 1. Oversampling Bit Decoding
OS[2:0] OSRATIOSNR
±10-V INPUT(dB)
SNR±5-V INPUT
(dB)
3-dB BANDWIDTH±10-V INPUT
(kHz)
3-dB BANDWIDTH±5-V INPUT
(kHz)
MAX THROUGHPUTPER CHANNEL
(kSPS)000 No OS 94.04 93.25 24 16 200001 2 95.95 94.91 23 15.7
100010 4 96.93 95.7 19.2 14.5 50011 8 99.04 97.35 11.2 10.6 25100
16 101.41 99.03 5.6 5.6 12.5101 32 103.5 100.76 2.8 2.8 6.25110 64
104.53 101.76 1.4 1.4 3.125111 Invalid — — — — —
In oversampling mode (see the Oversampling Mode of Operation
section), the ADC takes the first sample foreach channel at the
rising edge of the CONVSTA, CONVSTB signals. After converting the
first sample, thesubsequent samples are taken by an internally
generated sampling control signal. The samples are thenaveraged to
reduce the noise of the signal chain as well as to improve the SNR
of the ADC. The final output isalso decimated to provide a 18-bit
output for each channel. Table 1 lists the typical SNR performance
for boththe ±10-V and ±5-V input ranges, including the –3-dB
bandwidth and proportional maximum throughput perchannel. When the
oversampling ratio increases, there is a proportional improvement
in the SNR performanceand decrease in the bandwidth of the input
filter.
7.3.8 ReferenceThe ADS8598S can operate with either an internal
voltage reference or an external voltage reference using aninternal
gain amplifier. The internal or external reference selection is
determined by an external REFSEL pin, asexplained in the REFSEL
(Input) section. The REFIN/REFOUT pin outputs the internal band-gap
voltage (ininternal reference mode) or functions as an input for
the external reference voltage (in external reference mode).In both
cases, the on-chip amplifier is always enabled. Use this internal
amplifier to gain the reference voltageand drive the actual
reference input of the internal ADC core for maximizing
performance. The REFCAPA (pin45) and REFCAPB (pin 44) pins must be
shorted together externally and a ceramic capacitor of 10 µF
(minimum)must be connected between this node and REFGND (pin 43) to
ensure that the internal reference buffer isoperating as closed
loop. Place this capacitor as close as possible to the device to
achieve rated performance.
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-
REFIO Initial Acuuracy (mV)
Num
ber
of H
its
050
100150200250300350400450500550600650700
-2.5 -2.2 -1.6 -1 -0.4 0.2 0.8 1.4 2 2.5
D048
ADC
2.5-V VREF
REFCAPB
REFIN/REFOUT
AGND
10 PFREFGND
10 PF
REFSEL
AVDD
REFCAPA
DVDD
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7.3.8.1 Internal ReferenceThe device has an internal 2.5-V
(nominal value) band-gap reference. In order to select the internal
reference,the REFSEL pin must be tied high or connected to DVDD.
When the internal reference is used, REFIN/REFOUT(pin 42) becomes
an output pin with the internal reference value. A 10-μF (minimum)
decoupling capacitor, asshown in Figure 57, is recommended to be
placed between the REFIN/REFOUT pin and REFGND (pin 43).
Thecapacitor must be placed as close to the REFIN/REFOUT pin as
possible. The output impedance of the internalband-gap creates a
low-pass filter with this capacitor to band-limit the noise of the
band-gap output. The use of asmaller capacitor increases the
reference noise in the system, thus degrading SNR and SINAD
performance. Donot use the REFIN/REFOUT pin to drive external ac or
dc loads because of the limited current output capabilityof the
pin. The REFIN/REFOUT pin can be used as a reference source if
followed by a suitable op amp buffer.
Figure 57. Device Connections for Using an Internal 2.5-V
Reference
The device internal reference is factory trimmed to a maximum
initial accuracy of ±2.5 mV. The histogram inFigure 58 shows the
distribution of the internal voltage reference output taken from
more than 2100 devices.
Figure 58. Internal Reference Accuracy at Room Temperature
Histogram
The initial accuracy specification for the internal reference
can be degraded if the die is exposed to anymechanical, thermal, or
environmental stress (such as humidity). Heating the device when
being soldered to aprinted circuit board (PCB) and any subsequent
solder reflow is a primary cause for shifts in the VREF value.
Themain cause of thermal hysteresis is a change in die stress and
therefore is a function of the package, die-attachmaterial, and
molding compound, as well as the layout of the device itself.
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-
Free-Air Temperature (qC)
RE
FIO
Vol
tage
(V
)
-40 -7 26 59 92 1252.495
2.497
2.499
2.501
2.503
2.505
D049
AVDD = 4.75 VAVDD = 5 VAVDD = 5.25 V
0
5
10
15
20
25
30
-4 -3 -2 -1 0 1
Num
ber
of D
evic
es
Error in REFIO Voltage (mV) C065
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In order to illustrate this effect, 80 devices were soldered
using lead-free solder paste with the suggestedmanufacturer reflow
profile, as explained in the AN-2029 Handling & Process
Recommendations applicationreport. The internal voltage reference
output is measured before and after the reflow process and Figure
59shows the typical shift in value. Although all tested units
exhibit a positive shift in the output voltages, negativeshifts are
also possible. The histogram in Figure 59 shows the typical shift
for exposure to a single reflow profile.Exposure to multiple
reflows, which is common on PCBs with surface-mount components on
both sides, causesadditional shifts in the output voltage. If the
PCB is to be exposed to multiple reflows, solder the ADS8598S inthe
last pass to minimize device exposure to thermal stress.
Figure 59. Solder Heat Shift Distribution Histogram
The internal reference is also temperature compensated to
provide excellent temperature drift over an extendedindustrial
temperature range of –40°C to +125°C. Figure 60 shows the variation
of the internal reference voltageacross temperature for different
values of the AVDD supply voltage. The typical specified value of
the referencevoltage drift over temperature is 7.5 ppm/°C.
Figure 60. Variation of Internal Reference Output (REFIN/REFOUT)
vs Free-Air Temperature and Supply
7.3.8.2 External ReferenceFor applications that require a
reference voltage with lower temperature drift or a common
reference voltage formultiple devices, the ADS8598S offers a
provision to use an external reference, using the internal buffer
to drivethe ADC reference pin. In order to select the external
reference mode, either tie the REFSEL pin low or connectthis pin to
AGND. In this mode, an external 2.5-V reference must be applied at
REFIN/REFOUT (pin 42), whichbecomes a high-impedance input pin. Any
low-drift, small-size external reference can be used in this
modebecause the internal buffer is optimally designed to handle the
dynamic loading on the ADC reference input. Theoutput of the
external reference must be filtered to minimize the resulting
effect of the reference noise on systemperformance. Figure 61
illustrates a typical connection diagram for this mode.
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-
Free-Air Temperature (qC)
RE
FC
AP
Vol
tage
(V
)
-40 -7 26 59 92 1253.99
3.995
4
4.005
4.01
D051
AVDD = 4.75 VAVDD = 5 VAVDD = 5.25 V
REFCAP Drift (ppm/qC)
Num
ber
of h
its
0
1
2
3
4
5
6
7
8
0 0.665 1.325 1.985 2.645 3.305 4
D052
ADC
2.5-V VREF
REFCAPB
REFIN/REFOUT
AGND
10 PF
REFGND
CREF
REFSEL
AVDD
REF5025(Refer to Device
Datasheet for Detailed Pin Configuration)
AVDD
OUT
REFCAPA
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Figure 61. Device Connections for Using an External 2.5-V
Reference
For closed-loop operation of the internal reference buffer, the
REFCAPA and REFCAPB pins must be externallyshorted together. The
output of the internal reference buffer appears at the REFCAP pin.
A minimumcapacitance of 10 µF must be placed between the REFCAPA,
REFCAPB pins and REFGND (pin 43). Place thiscapacitor as close as
possible to the REFCAPA and REFCAPB pins. Do not use this internal
reference buffer todrive external ac or dc loads because of the
limited current output capability.
Figure 62 shows that the performance of the internal buffer
output is very stable across the entire operatingtemperature range
of –40°C to +125°C. Figure 63 shows that the typical specified
value of the reference bufferdrift over temperature is 5
ppm/°C.
Figure 62. Variation of Reference Buffer Output(REFCAPA,
REFCAPB) vs Free-Air Temperature and
Supply
Number of samples = 30
Figure 63. Reference Buffer Temperature Drift Histogram
7.3.8.3 Supplying One VREF to Multiple DevicesFor applications
that require multiple ADS8598S devices, using the same reference
voltage source for all ADCshelps eliminate any potential errors in
the system resulting from mismatch between multiple reference
sources.
Figure 64 illustrates the recommended connection diagram for an
application that uses one device in internalreference mode and
provides the reference source for other devices. The device used as
source of the voltagereference is bypassed by a 10-µF capacitor on
the REFIN/REFOUT pin, whereas the other devices are bypassedwith a
100-nF capacitor.
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-
REFSEL
REFIN / REFOUT
100 nF
ADS8598S
REFSEL
REFIN / REFOUT
100 nF
ADS8598S
REFSEL
REFIN / REFOUT
100 nF
ADS8598S
REFGND REFGND REFGND
CREF
REF5025(Refer to Device
Datasheet for Detailed Pin Configuration)
AVDD
OUT
Copyright © 2016, Texas Instruments Incorporated
REFSEL
DVDD
REFIN / REFOUT
10PF
ADS8598S
REFSEL
REFIN / REFOUT
100nF
ADS8598S
REFSEL
REFIN / REFOUT
100nF
ADS8598S
REFGND REFGND REFGND
Configured as Output Configured as Input Configured as Input
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Figure 64. Multiple Devices Connected With an Internal Reference
From one Device
Figure 65 shows the recommended connection diagram for an
application that uses an external voltagereference (such as the
REF5025) to provide the reference source for multiple devices.
Figure 65. Multiple Devices Connected Using an External
Reference
7.3.9 ADC Transfer FunctionThe ADS8598S is a multichannel device
that supports two single-ended, bipolar input ranges of ±10 V and
±5 Von all input channels. The device outputs 18 bits of conversion
data in binary two's complement format for bothbipolar input
ranges. The format for the output codes is the same across all
analog channels.
Figure 66 depicts the ideal transfer characteristic for each ADC
channel for all input ranges. The full-scale range(FSR) for each
input signal is equal to the difference between the positive
full-scale (PFS) input voltage and thenegative full-scale (NFS)
input voltage. The LSB size is equal to FSR / 218 = FSR / 262144
because theresolution of the ADC is 18 bits. Table 2 lists the LSB
values corresponding to the different input ranges.
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-
1000 «�«�0000(20000h)
0111 «�«�1111(1FFFFh)
0000 «�«�0000(00000h)
PFS ± 1.5LSB
0V-0.5LSBNFS+0.5LSB
AD
C O
utpu
t Cod
e
Analog Input (AIN_nP t AIN_nGND)
NFS PFS
FSR = PFS - NFS
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Figure 66. 18-Bit ADC Transfer Function (Two's Complement Binary
Format)
Table 2. ADC LSB Values for Different Input Ranges
INPUT RANGE (V) POSITIVE FULL-SCALE(V)NEGATIVE FULL-SCALE
(V) FULL-SCALE RANGE (V) LSB (µV)
±10 10 –10 20 76.295±5 5 –5 10 38.1475
7.3.10 ADS8598S Device Family ComparisonThe ADS8598S belongs to
a family of pin-compatible devices. Table 3 lists the devices from
this family alongwith their features.
Table 3. Device Family ComparisonPRODUCT RESOLUTION (Bits)
CHANNELS SAMPLE RATE (kSPS)ADS8598H 18 8, single-ended 500ADS8588H
16 8, single-ended 500ADS8588S 16 8, single-ended 200ADS8586S 16 6,
single-ended 250ADS8584S 16 4, single-ended 330ADS8578S 14 8,
single-ended 200
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7.4 Device Functional Modes
7.4.1 Device Interface: Pin Description
7.4.1.1 REFSEL (Input)The REFSEL pin is a digital input pin that
enables selection between the internal and external reference mode
ofoperation for the device. If the REFSEL pin is set to logic high,
then the internal reference is enabled andselected. If this pin is
set to logic low, then the internal band-gap reference circuit is
disabled and powered down.In this mode, an extern