FOR INFORMATION PURPOSES ONLY FeaTures DescripTion

LT5503

15503fa

For more information www.linear.com/LT5503

Typical applicaTion

FeaTures DescripTion

1.2GHz to 2.7GHz Direct IQ Modulator and Mixer

The LT®5503 is a front-end transmitter IC designed for low voltage operation. The IC contains a high frequency quadrature modulator with a variable gain amplifier (VGA) and a balanced mixer. The modulator includes a precision 90° phase shifter which allows direct modulation of an RF signal by the baseband I and Q signals.

In a superheterodyne system, the mixer can be used to generate the high frequency RF input for the modulator by mixing the system’s 1st and 2nd local oscillators.

The LT5503 modulator output P 1dB is –3dBm at 2.5GHz. The VGA allows output power reduction in three steps up to 13dB with digital control. The baseband inputs are internally biased for maximum input voltage swing at low supply voltage. If needed, they can be driven with external bias voltages.

2.45GHz Transmitter Application, Carrier for Modulator Generated by Upmixer

applicaTions

n Single 1.8V to 5.25V Supply n Direct IQ Modulator with Integrated 90° Phase

Shifter* n 4-Step RF Power Control n 120MHz Modulation Bandwidth n Independent Double-Balanced Mixer n Modulation Accuracy Insensitive to Carrier Input

Power n Modulator I/Q Inputs Internally Biased n Available in 20-Lead FE Package

n IEEE 802.11 DSSS and FHSS n High Speed Wireless LAN (WLAN) n Wireless Local Loop (WLL) n PCS Wireless Data n MMDS

MODOUT0°

90°÷2

÷1

CONTROLLOGIC

GC1 GC2GND

MX– MX+

LO2

2.45GHzBPF

VCC12VVCC2

2V

2.45GHzMODULATED

RFOUTBI+ BI–

BQ+ BQ–

VCCMODVCCRFVCCLO1VCCLO2 MODIN

LT5503

VCCVGA

LO1

LO1IN (2075MHz)

LO2IN(750MHz)

DMODE

MIXEN

MODEN

MIXERENABLE

MODULATORENABLE

5503 TA01

VGA

I, Q DIFFERENTIAL INPUT VOLTAGE (VP-P)0.01

SSB

OUTP

UT P

OWER

(dBm

)

1

0

–5

–10

–15

–20

–25

–30

–35

–40

–45

5503 G04

0.1 10

5.25 VDC 3 VDC1.8 VDC

SSB Output Power vs I, Q Amplitude

L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Patents pending.

OBSOLETE:FOR INFORMATION PURPOSES ONLYContact Linear Technology for Potential Replacement

http://www.linear.com/LT5503


LT5503

25503fa


absoluTe MaxiMuM raTings

Supply Voltage ........................................................ 5.5VControl Voltages .......................... –0.3V to (VCC + 0.3V)Baseband Voltages (BI+ to BI– and BQ+ to BQ–) .......±2VBaseband Common Mode Voltage .....1V to (VCC – 0.3V)LO1 Input Power ....................................................4dBmLO2 Input Power ....................................................4dBmMODIN Input Power ...............................................4dBmOperating Temperature Range ................. –40°C to 85°CStorage Temperature Range .................. –65°C to 150°CLead Temperature (Soldering, 10 sec) ................... 300°C

(Note 1)

orDer inForMaTionLEAD FREE FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE

OBSOLETE PART

LT5503EFE#PBF LT5503EFE#TRPBF 5503 20-Lead Plastic TSSOP –40°C to 85°C

Consult LTC Marketing for parts specified with wider operating temperature ranges. Consult LTC Marketing for information on non-standard lead based finish parts.For more information on lead free part marking, go to: http://www.linear.com/leadfree/ For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/

pin conFiguraTion

1

2

3

4

5

6

7

8

9

10

TOP VIEW

20

19

18

17

16

15

14

13

12

11

BQ–

BQ+

GC1

MODIN

VCCMOD

VCCRF

LO1

VCCLO1

DMODE

MX+

BI–

BI+

GC2

MODOUT

VCCVGA

VCCLO2

LO2

MODEN

MIXEN

MX–

FE PACKAGE20-LEAD PLASTIC TSSOP

21

TJMAX = 150°C, θJA = 38°C/W

EXPOSED PAD IS GND (PIN 21)MUST BE SOLDERED TO PCB


LT5503

35503fa


elecTrical characTerisTics (I/Q Modulator) VCC1 = 3VDC, 2.4GHz matching, MODEN = High, GC1 = GC2 = Low, TA = 25°C, MODRFIN = 2.45GHz at –16dBm, [I – IB] and [Q – QB] = 100kHz CW signal at 1VP-P differential, Q leads I by 90°, unless otherwise noted. (Test circuit shown in Figure 2.) (Note 3)

PARAMETER CONDITIONS MIN TYP MAX UNITS

RF Carrier Input (MODRFIN)

Frequency Range2 Requires Appropriate Matching 1.2 to 2.7 GHz

Input VSWR ZO = 50Ω 1.3:1

Input Power –20 to –10 dBm

Baseband Inputs (BI+, BI–, BQ+, BQ–)

Frequency Bandwidth (3dB) 120 MHz

Differential Input Voltage for 1dB Compressed Output 1 VP-P

DC Common Mode Voltage Internally Biased 1.4 VDC

Differential Input Resistance 18 kΩ

Input Capacitance 0.8 pF

Gain Error ±0.2 dB

Phase Error ±1 DEG

Modulated RF Carrier Output (MODRFOUT)

Output Power, Max Gain –6 –3 dBm

Output VSWR ZO = 50Ω 1.5:1

Image Suppression –26 –34 dBc

Carrier Suppression –24 –32 dBc

Output 1dB Compression –3 dBm

Output 3rd Order Intercept f1 = 100kHz, fQ = 120kHz 2 dBm

Output 2rd Order Intercept f1 = 100kHz, fQ = 120kHz 16 dBm

Broadband Noise 20MHz Offset –142 dBm/Hz

VGA Control Logic (GC2, GC1)

Switching Time 100 ns

Input Current 2 µA

Input Low Voltage 0.4 VDC

Input High Voltage 1.7 VDC

Output Power Attenuation GC2 = Low, GC1 = High 4.5 dB

Output Power Attenuation GC2 = High, GC1 = Low 9 dB

Output Power Attenuation GC2 = High, GC1 = High 13.5 dB

Modulator Enable (MODEN) Low = Off, High = On

Turn ON/OFF Time 1 µs

Input Current 105 µA

Enable VCC – 0.4 VDC

Disable 0.4 VDC

Modulator Power Supply Requirements

Supply Voltage 1.8 5.25 VDC

Modulator Supply Current MODEN = High 29 38 mA

Modulator Shutdown Current MODEN = Low 50 µA


LT5503

45503fa


elecTrical characTerisTics

VCC2 = 3VDC, 2.4GHz matching, MIXEN = High, DMODE = Low (LO2 ÷ 2 mode), TA = 25°C, LO2IN = 750MHz at –18dBm, LO1IN = 2075MHz at –12dBm. MIXRFOUT measured at 2450MHz, unless otherwise noted. (Test circuit shown in Figure 2.) (Note 3)

(Mixer)

PARAMETER CONDITIONS MIN TYP MAX UNITS

Mixer 2nd LO Input (LO2IN)

Frequency Range Internally Matched 50 to 1000 MHz


Input Power –20 to –12 dBm

Mixer 1st LO Input (LO1IN)

Frequency Range2 Requires Appropriate Matching 1400 to 2400 MHz


Input 3rd Order Intercept –30dBm/Tone, ∆f = 200kHz –12 dBm

Mixer RF Output (MIXRFOUT)

Frequency Range2 Requires Appropriate Matching 1700 to 2700 MHz

Output VSWR ZO = 50Ω 1.5:1

Small-Signal Conversion Gain PLO1 = –30dBm 5 dB

Output Power –14.7 –12.7 dBm

LO1 Suppression –22 –29 dBc

Output 1dB Compression –15 dBm

Broadband Noise 20MHz Offset –152 dBm/Hz

LO2 Divider Mode Control (DMODE) Low = fLO2 ÷ 2, High = fLO2 ÷ 1

Input Current 1 µA

Input Low Voltage (÷2) 0.4 VDC

Input High Voltage (÷1) VCC – 0.4 VDC

Mixer Enable (MIXEN) Low = Off, High = On

Turn ON/OFF Time 1 µs

Input Current 130 µA

Enable VCC – 0.4 VDC

Disable 0.4 VDC

Mixer Power Supply Requirements

Supply Voltage 1.8 5.25 VDC

Supply Current (÷2 mode) DMODE = Low, MIXEN = High 11.9 15.5 mA

Supply Current (÷1 mode) DMODE = High, MIXEN = High 10.8 mA

Shutdown Current MIXEN = Low 10 µA

Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and lifetime.

Note 2: External component values on the final test circuit shown in Figure 2 are optimized for operation in the 2.4GHz to 2.5GHz band.Note 3: Specifications over the –40°C to 85°C temperature range are assured by design, characterization and correlation with statistical process controls.


LT5503

55503fa


Typical perForMance characTerisTics

Modulator Supply Current vs Supply Voltage

Modulator Shutdown Current vs Supply Voltage

MODEN Current vs Enable Voltage

Baseband Frequency Response I/Q Amplitude = 1VP-P

Typical SSB Spectrum

MODRFIN and MODRFOUT Return Loss 2.4GHz Matching

VCC1 = 3VDC, 2.4GHz matching, MODEN = high, GC1 = GC2 = low (max gain), TA = 25°C, MODRFIN = 2.45GHz at –16dBm, (I–IB) and (Q–QB) = 100kHz sine at 1VP-P differential, Q leads I by 90°, unless otherwise noted. (Test circuit shown in Figure 2.)

(I/Q Modulator)

2.45GHz Modulated Output Power vs Supply Voltage

VCC1 SUPPLY VOLTAGE (V)1.8

SUPP

LY C

URRE

NT (m

A)

3.2 4.6 5.3

38

36

34

32

30

28

26

24

22

20

5503 G01

2.5 3.9

TA = 85°C

TA = 25°C

TA = –40°C


SHUT

DOW

N CU

RREN

T (µ

A)

3.2 4.6 5.3

100

10

1

0.1

5503 G02

2.5 3.9

TA = 85°C

TA = 25°C

TA = –40°C

MODEN = LOW

MODEN VOLTAGE (V)1.8

INPU

T CU

RREN

T (µ

A)

3.2 4.6 5.3

220

200

180

160

140

120

100

80

60

40

5503 G03

2.5 3.9

TA = 85°C

TA = –40°C

MODEN = VCC1

TA = 25°C

SUPPLY VOLTAGE (V)1.8

OUTP

UT P

OWER

(dBm

)

–2

–3

–4

–5

–62.4 3.0 3.6 4.2

5503 TA01b

4.8 5.4

PLO1 = –12dBmPLO2 = –18dBmBASEBAND = 1VP-PTA = 25°C

I, Q INPUT FREQUENCY (MHz)

OUT

PUT

POW

ER (d

Bm)

1

0

–5

–10

–15

–20

–25

–30

–35

–40

5503 G05

0.1 10

IMAGE

CARRIER

DESIREDSIDEBAND

FREQUENCY (MHz)2050

RETU

RN L

OSS

(dB)

–20

–10

2850

5503 G06

–30

–402250 2450 2650

0

MODRFOUT

MODRFIN

FREQUENCY (MHz)

0

–10

–20

–30

–40

–50

–60

–70

–80

–90

–100

P OUT

(dBm

)

5503 G07

2449.6 2449.8 2450.0 2450.2 2450.4 2450.6


LT5503

65503fa



SSB Output Power vs Input Power VCC1 = 1.8V

Carrier Suppression vs Input Power VCC1 = 1.8V

SSB Output Power vs Input Power VCC1 = 3V

Carrier Suppression vs Input Power VCC1 = 3V

Image Suppression vs Input Power VCC1 = 3V

SSB Output Power vs Input Power VCC1 = 5.25V

Carrier Suppression vs Input Power VCC1 = 5.25V

Image Suppression vs Input Power VCC1 = 5.25V

Image Suppression vs Input Power VCC1 = 1.8V

2.4GHz matching, MODEN = high, GC1 = GC2 = low (max gain), MODRFIN = 2.45GHz, (I–IB) and (Q–QB) = 100kHz sine at 1VP-P differential, Q leads I by 90°, unless otherwise noted. (Test circuit shown in Figure 2.)

(I/Q Modulator)

MODRFIN INPUT POWER (dBm)–24 –22 –20 –18 –16 –14 –12 –10

SSB

OUTP

UT P

OWER

(dBm

)

–2

–4

–6

–8

–10

–12

–14

–16

–18

–20

5503 G08

TA = 85°C

TA = 25°C

TA = –40°C


CARR

IER

SUPP

RESS

ION

(dBc

)

–20

–30

–40

–50

5503 G09

TA = 85°C

TA = 25°C

TA = –40°C


IMAG

E SU

PPRE

SSIO

N (d

Bc)

–20

–30

–40

–50

5503 G10

TA = 85°C

TA = 25°C

TA = –40°C


SSB

OUTP

UT P

OWER

(dBm

)

0

–2

–4

–6

–8

–10

–12

–14

–16

–18

5503 G11

TA = 85°C

TA = 25°C

TA = –40°C


CARR

IER

SUPP

RESS

ION

(dBc

)

–20

–30

–40

–50

5503 G12

TA = 85°C

TA = 25°C

TA = –40°C


IMAG

E SU

PPRE

SSIO

N (d

Bc)

–20

–30

–40

–50

5503 G13

TA = 85°C

TA = 25°CTA = –40°C


SSB

OUTP

UT P

OWER

(dBm

)

0

–2

–4

–6

–8

–10

–12

–14

–16

–18

5503 G14

TA = 85°C

TA = 25°C

TA = –40°C


CARR

IER

SUPP

RESS

ION

(dBc

)

–20

–30

–40

–50

5503 G15

TA = 85°C

TA = 25°C

TA = –40°C


IMAG

E SU

PPRE

SSIO

N (d

Bc)

–20

–30

–40

–50

5503 G16

TA = 85°C

TA = 25°C

TA = –40°C


LT5503

75503fa



Output Power vs Frequency 1.2GHz Matching

Carrier Feedthrough vs Frequency1.2GHz Matching

SSB Image vs Frequency1.2GHz Matching

Output Power vs Frequency1.9GHz Matching



Output Power vs Frequency2.4GHz Matching



VCC1 = 3VDC, MODEN = high, TA = 25°C, PMODRFIN = –16dBm, (I–IB) and (Q–QB) = 100kHz sine at 1VP-P differential, Q leads I by 90°, unless otherwise noted. (Test circuit shown in Figure 2.)

(I/Q Modulator)

MODRFIN FREQUENCY (MHz)1000 1100 1200 1300 1400

SSB

OUTP

UT P

OWER

(dBm

)

0

–2

–4

–6

–8

–10

–12

–14

–16

–18

–20

5503 G17

GC2, GC1 = 00

01

11

10


5503 G18

CARR

IER

(dBm

)

–30

–40

–50

–60

GC2, GC1 = 00

10

11

01


5503 G19

IMAG

E (d

Bm)

–30

–40

–50

–60

GC2, GC1 = 00

10

11

01


SSB

OUTP

UT P

OWER

(dBm

)

2

0

–2

–4

–6

–8

–10

–12

–14

–16

–18

5503 G20

GC2, GC1 = 00

01

10

11


5503 G21

CARR

IER

(dBm

)

–30

–40

–50

–60

GC2, GC1 = 00

10

11

01


5503 G22

IMAG

E (d

Bm)

–30

–40

–50

–60

GC2, GC1 = 00

10

11

01

MODRFIN FREQUENCY (MHz)2250 2350 2450 26502550

SSB

OUTP

UT P

OWER

(dBm

)

0

–2

–4

–6

–8

–10

–12

–14

–16

–18

5503 G23

GC2, GC1 = 00

01

10

11


5503 G24

GC2, GC1 = 00

01

10

11

CARR

IER

(dBm

)

–30

–40

–50

–60


5503 G25

GC2, GC1 = 00

10

11

IMAG

E (d

Bm)

–30

–40

–50

–60

01


LT5503

85503fa



Mixer Supply Current vs Supply Voltage (LO2 ÷ 2 Mode)

Mixer Supply Current vs Supply Voltage (LO2 ÷ 1 Mode)

Mixer Shutdown Current vs Supply Voltage

RF Output Power vs LO1 Input Power (VCC2 = 1.8V)

RF Output Power vs LO1 Input Power (VCC2 = 3V)

RF Output Power vs LO1 Input Power (VCC2 = 5.25V)

LO1 Feedthrough vs LO1 Input Power (VCC2 = 1.8V)

LO1 Feedthrough vs LO1 Input Power (VCC2 = 3V)

LO1 Feedthrough vs LO1 Input Power (VCC2 = 5.25V)

2.4GHz matching, MIXEN = high, DMODE = low (LO2 ÷ 2 mode), LO2IN = 750MHz at –18dBm, LO1IN = 2075MHz. MIXRFOUT measured at 2450MHz, unless otherwise noted. (Test circuit shown in Figure 2.)

(Mixer)


SUPP

LY C

URRE

NT (m

A)

14

13

12

11

10

9

82.5 3.2 4.63.9

5503 G26

5.3

TA = 85°C

TA = 25°C

TA = –40°C


SUPP

LY C

URRE

NT (m

A)

14

13

12

11

10

9

82.5 3.2 4.63.9

5503 G27

5.3

TA = 85°C

TA = 25°C

TA = –40°C

DMODE = HIGH


SHUT

DOW

N CU

RREN

T (µ

A)

100

10

1

0.12.5 3.2 4.63.9

5503 G28

5.3

TA = 85°C

TA = 25°C TA = –40°C

MIXEN = LOW

LO1IN POWER (dBm)–30

MIX

RFOU

T PO

WER

(dBm

)

–6

1195 G29

–24 –18 –12 –9–27 –21 –15

–12

–14

–16

–18

–20

–22

–24

–26

–28

TA = 85°C

TA = –40°C

TA = 25°C


MIX

RFOU

T PO

WER

(dBm

)

–6

1195 G30

–24 –18 –12 –9–27 –21 –15

–12

–14

–16

–18

–20

–22

–24

–26

–28

TA = 85°C

TA = –40°C

TA = 25°C


MIX

RFOU

T PO

WER

(dBm

)

–6

1195 G31

–24 –18 –12 –9–27 –21 –15

–12

–14

–16

–18

–20

–22

–24

–26

–28

TA = 85°C

TA = –40°C

TA = 25°C


LO1

FEED

THRO

UGH

(dBc

)

–6

1195 G32

–24 –18 –12 –9–27 –21 –15

–20

–25

–30

–35

–40

TA = 85°C

TA = –40°C

TA = 25°C


LO1

FEED

THRO

UGH

(dBc

)

–6

1195 G33

–24 –18 –12 –9–27 –21 –15

–20

–25

–30

–35

–40

TA = 85°C

TA = –40°CTA = 25°C


LO1

FEED

THRO

UGH

(dBc

)

–6

1195 G34

–24 –18 –12 –9–27 –21 –15

–20

–25

–30

–35

–40

TA = 85°C

TA = –40°C

TA = 25°C


LT5503

95503fa



RF Output Power and LO1 Feedthrough 1.9GHz Matching

Small-Signal Conversion Gain and IIP3 1.9GHz Matching

LO1IN and MIXRFOUT Return Loss 1.9GHz Matching

RF Output Power and LO1 Feedthrough 2.4GHz Matching

Small-Signal Conversion Gain and IIP3 2.4GHz Matching

LO1 and MIXRFOUT Return Loss 2.4GHz Matching

MIXEN Input Current vs Enable Voltage (MIXEN = VCC2)

VCC2 = 3VDC, MIXEN = high, DMODE = low (LO2 ÷ 2mode), TA = 25°C, unless otherwise noted. (Test circuit shown in Figure 2.)(Mixer)

RF OUTPUT FREQUENCY (MHz)1650

RF O

UTPU

T (d

Bm)

–12

–14

–16

–18

–20

–22

0

–10

–20

–30

–40

–502050

5503 G35

1750 1850 1950 2150

OUTPUTPOWER

LO1FEEDTHROUGH

LO2IN = 480MHz AT –18dBmLO1IN = fRF –240MHz AT –12dBm

LO1 (dBc)


CONV

ERSI

ON G

AIN

(dB)

6

4

2

0

–2

–4

–3

–6

–9

–12

–15

–182050

5503 G36

1750 1850 1950 2150

IIP3

SMALL-SIGNALCONVERSIONGAIN

LO2IN = 480MHz AT –18dBmLO1IN = fRF –240MHz AT –30dBm/TONE

IIP3 (dBm)

FREQUENCY (MHz)1100

RETU

RN L

OSS

(dB)

0

–5

–10

–15

–20

–25

–301700 2100

5503 G37

1300 1500 1900 2300 2500

LO1IN

MIXRFOUT


RF O

UTPU

T (d

Bm)

–12

–14

–16

–18

–20

–22

0

–10

–20

–30

–40

–502650

5503 G38

2350 2450 2550

LO1FEEDTHROUGH

OUTPUT POWER

LO2IN = 750MHz AT –18dBmLO1IN = fRF –375MHz AT –12dBm

LO1 (dBc)


CONV

ERSI

ON G

AIN

(dB)

6

4

2

0

–2

–4

–3

–6

–9

–12

–15

–182650

5503 G39

2350 2450 2550

IIP3

SMALL-SIGNALCONVERSIONGAIN

LO2IN = 750MHz AT –18dBmLO1IN = fRF –375MHz AT –30dBm/TONE

IIP3 (dBm)

FREQUENCY (MHz)1450

RETU

RN L

OSS

(dB)

0

–5

–10

–15

–20

–25

–302050 2450

5503 G40

1650 1850 2250 2650 2850

LO1

MIXRFOUT

MIXEN VOLTAGE (V)1.8

INPU

T CU

RREN

T (µ

A)

3.2 4.6 5.3

300

270

240

210

180

150

120

90

60

30

5503 G41

2.5 3.9

TA = 85°C

TA = –40°C

TA = 25°C


LT5503

105503fa


pin FuncTionsBQ– (Pin 1): Negative Baseband Input Pin of the Modulator Q-Channel. This pin is internally biased to 1.4V, but can also be overdriven with an external DC voltage greater than 1.4V, but less than VCC – 0.4V.

BQ+ (Pin 2): Positive Baseband Input Pin of Modulator Q-Channel. This pin is internally biased to 1.4V, but can also be overdriven with an external DC voltage greater than 1.4V, but less than VCC – 0.4V.

GC1 (Pin 3): Gain Control Pin. This pin is the least signifi-cant bit of the 4-step modulator gain control.

MODIN (Pin 4): Modulator Carrier Input Pin. This pin is internally biased and should be AC-coupled. An external matching network is required for a 50Ω source.

VCCMOD (Pin 5): Power Supply Pin for the I/Q Modulator. This pin should be externally connected to the other VCC pins and decoupled with 1000pF and 0.1µF capacitors.

VCCRF (Pin 6): Power Supply Pin for the I/Q Modulator Input RF Buffer and Phase Shifter. This pin should be externally connected to the other VCC pins and decoupled with 1000pF and 0.1µF capacitors.

LO1 (Pin 7): Mixer 1st LO Input Pin. This pin is internally biased and should be AC-coupled. An external matching network is required for a 50Ω source.

VCCLO1 (Pin 8): Power Supply Pin for the Mixer LO1 Cir-cuits. This pin should be externally connected to the other VCC pins and decoupled with 1000pF and 0.1µF capacitors.

DMODE (Pin 9): Mixer 2nd LO Divider Mode Control Pin. Low = divide-by-2, High = divide-by-1.

MX+ (Pin 10): Mixer Positive RF Output Pin. This pin must be connected to VCC through an external matching network.

MX– (Pin 11): Mixer Negative RF Output Pin. This pin must be connected to VCC through an external matching network.

MIXEN (Pin 12): Mixer Enable Pin. When the input volt-age is higher than VCC – 0.4V, the mixer circuits supplied through pins 8, 10, 11 and 15 are enabled. When the input voltage is less than 0.4V, these circuits are disabled.

MODEN (Pin 13): Modulator Enable Pin. When the input voltage is higher than VCC – 0.4V, the modulator circuits supplied through pins 5, 6, 16 and 17 are enabled. When the input voltage is less than 0.4V, these circuits are disabled.

LO2 (Pin 14): Mixer 2nd LO Input Pin. This pin is internally biased and should be AC-coupled. An external matching network is not required, but can be used for improved matching to a 50Ω source.

VCCLO2 (Pin 15): Power Supply Pin for the Mixer LO2 Circuits. This pin should be externally connected to the other VCC pins and decoupled with 1000pF and 0.1µF capacitors.

VCCVGA (Pin 16): Power Supply Pin for the Modulator Variable Gain Amplifier. This pin should be externally connected to the other VCC pins through a 47Ω resistor and decoupled with a good high frequency capacitor (2pF typical) placed close to the pin.

MODOUT (Pin 17): Modulator RF Output Pin. This pin must be externally biased to VCC through a bias choke. An external matching network is required to match to 50Ω.

GC2 (Pin 18): Gain Control Pin. This pin is the most sig-nificant bit of the 4-step modulator gain control.

BI+ (Pin 19): Positive Baseband Input Pin of the Modulator I-Channel. This pin is internally biased to 1.4V, but can also be overdriven with an external DC voltage greater than 1.4V, but less than VCC – 0.4V.

BI– (Pin 20): Negative Baseband Input Pin of the Modulator I-Channel. This pin is internally biased to 1.4V, but can also be overdriven with an external DC voltage greater than 1.4V, but less than VCC – 0.4V.

Exposed Pad (Pin 21): Circuit Ground Return for the En-tire IC. This must be soldered to the printed circuit board ground plane.


LT5503

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block DiagraM

0°90°

5503 BD

MIXER BIAS CIRCUITS

MODULATOR BIAS CIRCUITS

LO1BUFFER

RFBUFFER

CONTROLLOCIC

VGA

V-I V-I

÷2LIM LIM÷1

21 10 11 9

7

8

4

5

2 1 20 19

16

17

18

3

13

12

15

14

6

BQ+ BI+BQ–

MX+ MX– DMODEGND(BACKSIDE)

BI–

VCCMOD

VCCVGA

MODOUT

GC2

GC1

MODEN

MIXEN

VCCLO2

LO2

VCCRF

MODIN

VCCLO1

LO1


LT5503

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TesT circuiT

20

19

18

17

16

15

14

13

12

11

LO1IN

LO2IN

1

2

3

4

5

6

7

8

9

10

LT5503

5503 F01

1

2 34

5C9

C138.2pF

C438.2pF

MIXRFOUT

T1

BQ–

BQ+

GC1

MODIN

VCCMOD

VCCRF

LO1

VCCLO1

DMODE

MX+

BI–

BI+

GC2

MODOUT

VCCVGA

VCCLO2

LO2

MODEN

MIXEN

MX–

C5 C6

C10

C201000pF

C161µF

C181µF

L6L5

MODEN

MIXEN

C151µF

C171µF

C221000pF

C12.2pF C7

C2

C190.01µF

C23

C14100pF

C3

GC1 GC2

MODRFINMODRFOUT

C11

C121000pF

C210.01µF

C4

VCC2

VCC1

VCC1

QB

Q

IB

I

L3

L4

DMODE

R247Ω

R1L1

L2

NOTE: VCC1 AND VCC2 POWER THE MODULATOR AND UPMIXER SECTIONS RESPECTIVELY.

GND

21 (BACKSIDE)

Application Dependent Component Values1.2GHz Matching (Modulator Only) 1.9GHz Matching 2.4GHz Matching

L1 33nH 22nH 18nHL2 12nH 5.6nH 2.7nHL3 12nH 4.7nH 2.7nHC2, C3, C7 39pF 15pF 8.2pFC10 2.7pF 1.8pF 1.2pFC23 n/a 1.5pF 1.5pFR1 240Ω 390Ω 390ΩC4 n/a 15pF 8.2pFC5, C6 n/a 1.8pF 2.2pFC9 n/a 15pF 2.7pFC11 n/a 2.2pF 1.2pFL4 n/a 6.8nH 4.7nHL5,L6 n/a 5.6nH 2.2nHT1 n/a LDB211G9010C-001 LDB212G4005C-001 Figure 1. Test Schematic for 1.2GHz, 1.9GHz and 2.4GHz Applications

TesT circuiT


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applicaTions inForMaTionThe LT5503 consists of a direct quadrature modulator and a mixer. The mixer operates over the range of 1.7GHz to 2.7GHz, and the modulator operates with an output range of 1.2GHz to 2.7GHz. The LT5503 is designed specifically for high accuracy digital modulation with supply voltages as low as 1.8V. It is suitable for IEEE 802.11b wireless local area network (WLAN), MMDS and wireless local loop (WLL) transmitters.

A dual-conversion RF system requires two local oscillators to convert signals between the baseband and RF domains (see Figure 2). The LT5503’s double-balanced mixer can be used to generate the LT5503 modulator’s high frequency carrier input (MODRFIN) by mixing the systems 1st and 2nd local oscillators (LO1 and LO2). In this case, a band-pass filter is required to select the desired mixer output for the modulator input. The mixer’s RF differential output produces –12dBm typically at 2.45GHz and the modula-tor MODIN pin requires ≥ –16dBm, driven single-ended. This allows approximately 4dB margin for bandpass filter

loss. The balanced output from the modulator is applied to a variable gain amplifier (VGA) that provides a single-ended output. Note that the modulator can also be used independently of the mixer, freeing the mixer to be used anywhere in the system. In this case, MODRFIN will be driven from an external frequency source.

Modulator Baseband

The baseband I and Q inputs (BI+/BI– and BQ+/BQ–) are internally biased to 1.4V to maximize the input signal range at low supply voltage. This bias voltage is stable over temperature, and increases by approximately 50mV at the maximum supply voltage. The modulator I and Q inputs have very wide bandwidth (120MHz typical), making the LT5503 suitable for even the most wideband modulation applications. For best carrier suppression and lowest distortion, differential input drive should be used. Single-ended drive is possible too, with the unused inputs AC-coupled to ground.

5503 F02

90°0°

0°

90°

÷2÷1

÷2

1ST LO 2ND LO

D/A

D/A

A/D

A/D

LT5502LT5506

LT5500

LT5503

LNA

I

I

Q

Q

VGA

Figure 2. Example System Block Diagram for a Dual Conversion System


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applicaTions inForMaTionAC-Coupled Baseband. Figure 3 shows the simplified circuit schematic of a high-pass AC-coupled baseband interface.

5505 F03

18k

18k

0.8pF

0.8pF

0.8pF

0.8pF

BQ+

BQ–

BI+

BI–

CCPL

CCPL

CCPL

CCPL

Q

QB

I

IB

LT5503

Figure 3. AC-Coupled Baseband Interface

Figure 4. DC-Coupled Baseband Interface

With approximately 18k of differential input resistance, the suggested minimum AC-coupling capacitor can be determined using the following equation:

CCPL =

1(18 •103 • π • fC)

where fC is the 3dB cut-off frequency of the baseband input signal.

A larger capacitor may be used where the settling time of charging and discharging the AC-coupling capacitor is not critical.

DC-Coupled Baseband. The baseband inputs’ internal bias voltage can be overdriven with an external bias circuit. This facilitates direct interfacing to a D/A converter for faster transient response. In this case, the LT5503’s baseband inputs are DC biased by the converter. The optimal VBIAS is 1.4V, independent of VCC. In general, the maximum VBIAS should be less than VCC – 0.4V. The DC load on each converter output can be approximated using the following equation where IINPUT is the current flowing into a modulator input:

IINPUT =

VBIAS −1.4V9kΩ

Figure 4 shows a simplified circuit schematic for in-terfacing the LT5503’s baseband inputs to the outputs of a D/A converter. OIP and OIN are the positive and negative baseband outputs, respectively, of the converter’s I-channel. Similarly, OQP and OQN are the positive and negative baseband outputs, respectively, of the converter’s Q-channel.

5505 F04

18k

18k

0.8pF

0.8pF

0.8pF

0.8pF

BQ+

BQ–

BI+

BI–

LT5503IINPUT

IINPUT

IINPUT

IINPUT

OIP

OIN

OQP

OQN

D/A

Modulator RF Input (MODRFIN)

The modulator RF input buffer is driven single ended. An internal active balun circuit produces balanced signals to drive the integrated phase shifter. Limiters following the phase shifter output accommodate a wide range of MODRFIN power, resulting in minimal degradation of modulation gain/phase accuracy performance or carrier feedthrough. This pin is easily matched to a 50Ω source with the simple lowpass network shown in Figure 1. This pin is internally biased, therefore an AC-coupling capaci-tor is required.

Modulator VGA (Variable Gain Amp)

The VGA has two digital selection lines to provide a nominal 0dB, 4.5dB, 9dB and 13.5dB attenuation from the maximum modulator output power setting. The logic table is shown below:

ATTENUATION

GC2

LOW HIGH

GC1 Low 0dB 9dB

High 4.5dB 13.5dB


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applicaTions inForMaTionPin 16 should be connected externally to VCC through a low value series resistor (47Ω typical). To assure proper output power control, a good, local high frequency AC ground for Pin 16 is essential. The MODOUT port of the VGA is an open collector configuration. An inductor with high self resonance frequency is required to connect Pin 17 to VCC as a DC return path, and as a part of the output matching network. Additional matching components are required to drive a 50Ω load as shown in Figure 1. The amplifier is designed to operate in Class A for low distor-tion performance. The typical output 1dB compression point (P1dB) is –3dBm at 2.45GHz. When the differential baseband input voltages are higher than 1VP-P, the VGA operates in Class AB mode, and the distortion performance of the modulator is degraded. The logic control inputs do not draw current when they are low. They draw about 2µA each when high.

Mixer LO1 Port

The mixer LO1 input port is the linear input to the mixer. It consists of an active balun amplifier designed to operate over the 1.4GHz to 2.4GHz frequency range. There is a lin-ear relationship between LO1 input power and MIXRFOUT power for LO1 input levels up to approximately – 20dBm. After that, the mixer output begins to compress. When operated in the recommended –14dBm to –8dBm input power range, the mixer is well compressed, which in turn creates a stable output level for the modulator input. As shown in Figure 1, a simple lowpass matching network is required to match this pin to 50Ω. This pin is internally biased, therefore an AC-coupling capacitor is required.

Mixer LO2 Port

The mixer LO2 port is designed to operate in the 50MHz to 1000MHz range. The first stage is a limiting amplifier. This stage produces the correct output levels to drive the internal divider circuit reliably, with LO2 input levels down to –20dBm. The output of the divider then drives another stage, which in turn switches the nonlinear inputs of the double-balanced mixer. Note that the mixer output will produce broadband noise if the LO2 signal level is too low. The input amplifier is designed for a good match over the entire frequency range. The only requirement (Figure 1) is an external AC-coupling capacitor.

Mixer Output Ports (MX+/MX–)

The mixer output is a differential open collector configura-tion. Bias current is supplied to these two pins through the center tap of a balun as shown in Figure 1. Simple lowpass matching is used to transform each leg of the mixer output to 25Ω for the balun’s 50Ω input impedance.

The balun approach provides the highest output power and best LO1 suppression, but is not absolutely neces-sary. It is also possible to match each output to 50Ω and couple power from one output. The unused output should be terminated in the same characteristic impedance. In this case, output power is approximately 2dB lower and LO1 suppression degrades to approximately 15dBc. A schematic for this approach is shown in Figure 6 where inductors LB+ and LB– supply bias current to the mixer’s differential outputs, and resistor RTERM terminates the unused output.

Figure 5. 50Ω Mixer Output Matching Without a Balun

1.9GHz 2.4GHz

L5,L6 5.6nH 2.7nH

C5, C6 1.8pF 0.68pF

C9 15pF 8.2pF

5503 F05

10 11

RTERM51Ω

LB+

MX+ MX–

LB–VCC

L5

C5C9

CBYPASS

C6

L6

MIXRFOUT


LT5503

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applicaTions inForMaTionEVALUATION BOARD

Figure 6 shows the circuit schematic of the evaluation board. The MODRFIN, MODRFOUT and MIXRFOUT ports are matched to 50Ω at 2.45GHz. The LO1IN port is matched to 50Ω at 2.1GHz and the LO2IN port is internally matched.

A 390Ω resistor is used to reduce the quality factor (Q) of the modulator output and deliver an output power of –3dBm typically. A lower value resistor may be used if the desired output power is lower. For example, the output power will be 3dB lower if a 200Ω resistor is used.

Inductors with high self-resonance frequency should be used for L1 to L6.

For simpler evaluation in a lab environment, the evaluation board includes op amps to convert single-ended I and Q input signals to differential . The op amp configuration has a voltage gain of two; therefore the peak baseband input voltage should be halved to maintain the same RF output power. The op amp configuration shown will maintain acceptable differential balance up to 10MHz typically. It is also possible to bypass the op amps and drive the modulator’s differential inputs directly by connecting to the four oversized vias on the board (V1, V2, V3 and V4).

Figure 6 also shows a table of matching network values for designs centered at 1.9GHz and 1.2GHz.

Figure 7 shows the evaluation board with connectors and ICs. Figure 8 shows the test set-up with the upconverting mixer and IQ modulator connected in a transmit configura-tion. Refer to the demo board DC365A Quick Start Guide for detailed testing information.

RF Layout Tips:

• Use 50Ω impedance transmission lines up to the matching networks, use of a ground plane is a must.

• Keep the matching networks as close to the pins as possible.

• Surface mount 0402 outline (or smaller) parts are recommended to minimize parasitic inductances and capacitances.

• Isolate the MODOUT pin from the LO2 input by putting the LO2 transmission line on the bottom side of the board.

• The only ground connection is through the exposed pad on the bottom of the package. This exposed pad must be soldered to the board in such a way to get complete RF contact.

• Low impedance RF ground connections are essential and can only be obtained by one or more vias tying directly into the ground plane.

• VCC lines must be decoupled with low impedance, broadband capacitors to prevent instability.

• Separate power supply lines should be used to isolate the MODIN signal and other stray signals from the MODOUT line. If possible, power planes should be used.

• Avoid use of long traces whenever possible. Long RF traces in particular can lead to signal radiation and degraded isolation, as well as higher losses.


LT5503

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applicaTions inForMaTion

Figure 6. Evaluation Circuit Schematic for 1.2GHz, 1.9GHz and 2.4GHz Applications

1

2

3

4

5

6

7

8

9

10

123456

121110987

20

19

18

17

16

15

14

13

12

11

LO1IN LO2IN

5503 F06

1

2 34

5*C9MIXER

OUTT1

BQ–

BQ+

GC1

MODIN

VCCMOD

VCCRF

LO1

VCCLO1

DMODE

MX+

BI–

BI+

GC2

MODOUT

VCCVGA

VCCLO2

LO2

MODEN

MIXEN

MX–

*C5 *C6

*C10

C201000pF

C181µF

*L6*L5

C411µFOPT

C421µFOPT

C394.7µF

C171µF

C334.7µF

C270.01µF

C324.7µF

C221000pF

C12.2pF

*C7 C190.01µF

*C23

*C2

C14100pF

*C3

MODRFIN

MODRFOUT

*C11

C121000pF

C210.01µF

C138.2pF

*C4

VCC2

VCC3

VCC2

VCC2

VCC1

VCC4

VCC4

VCC4

VCC4

VCC1

*L3

*L4

R247Ω

*R1*L1

*L2

21

C450.1µF

C244.7µF

C438.2pF

R42.7k

R82.7k

R720k

R620k

R520k

V1

E1

E4

E3

E2

V2 V4

V3

GND

J2

J7

J1 J4

J5

J6J3

LT5503

–

+

–

+

–

+

–

+

R356Ω1%

R2549.9Ω

R2110k1%

R2310k1%

R13510Ω1%

C344.7µF

R1256Ω1%

R16510Ω

1%

R15510Ω

1%

R14510Ω1%

5

6

5

6

7 7

8 8

U2-1LT1807

U2-2LT1807

U3-1LT1807

U3-2LT1807

4 4

2 2

3 3

1 1

C35, 39pF C36, 39pF

C38, 1pFC37, 1pF

R19510Ω1%

R2649.9Ω

R2749.9Ω

R17510Ω1%

C404.7µF

C151µF

C161µF R28

49.9Ω

R18510Ω1%

R20510Ω1% R22

10k1%

C290.01µF

C284.7µF

R2410k1%

SW1

Q-IN

R2910Ω

I-IN

*Application Dependent Component Values 1.2GHz Matching (Modulator Only) 1.9GHz Matching 2.4GHz MatchingL1 33nH 22nH 18nHL2 12nH 5.6nH 2.7nHL3 12nH 4.7nH 2.7nHC2, C3, C7 39pF 15pF 8.2pFC10 2.7pF 1.8pF 1.2pFC23 n/a 1.5pF 1.5pFR1 240 390 390C4 n/a 15pF 8.2pFC5, C6 n/a 1.8pF 2.2pFC9 n/a 15pF 2.7pFC11 n/a 2.2pF 1.2pFL4 n/a 6.8nH 4.7nHL5,L6 n/a 5.6nH 2.2nHT1 n/a LDB211G9010C-001 LDB212G4005C-001


LT5503

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QIN IIN

GND

GND

VCC4

VCC2 VCC3

VCC1

V2V1

V3 V4

LT1807 LT1807

LT5503IC

MODRFIN

LO1IN

MODRFOUT

LO2IN

MIXRFOUT

5503 F07

123456


Figure 7. LT5503 Evaluation Board Layout


LT5503

195503fa



QIN IIN

GND

GND VCC2 VCC3

VCC4

V2V1

V3 V4

LT1807 LT1807

LT5503IC

MODRFIN

LO1IN

MODRFOUT

LO2IN

MIXRFOUT

5503 F08

–

+

–

+

–

+

–

+

90°

0°DUAL SIGNALGENERATOR

SIGNALGENERATOR 1

SIGNALGENERATOR 1

123456

POWER SUPPLY 2

POWER SUPPLY 3

POWER SUPPLY 1

POWER SUPPLY 4

SPECTRUMANALYZER

EXTERNAL 3dBATTENUATOR PAD,OR 2.45GHz BPF

Figure 8. Test Set-Up for Upconverting Mixer and I/Q Modulator Transmit Chain Measurements.


LT5503

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package DescripTion

FE Package20-Lead Plastic TSSOP (4.4mm)

(Reference LTC DWG # 05-08-1663 Rev K)Exposed Pad Variation CB

Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings.

FE20 (CB) TSSOP REV K 0913

0.09 – 0.20(.0035 – .0079)

0° – 8°

0.25REF

RECOMMENDED SOLDER PAD LAYOUT

0.50 – 0.75(.020 – .030)

4.30 – 4.50*(.169 – .177)

1 3 4 5 6 7 8 9 10

DETAIL A

DETAIL A IS THE PART OFTHE LEAD FRAME FEATURE

FOR REFERENCE ONLYNO MEASUREMENT PURPOSE

111214 13

6.40 – 6.60*(.252 – .260)

3.86(.152)

2.74(.108)

20 1918 17 16 15

1.20(.047)MAX

0.05 – 0.15(.002 – .006)

0.65(.0256)

BSC0.195 – 0.30

(.0077 – .0118)TYP

2

2.74(.108)

0.45 ±0.05

0.65 BSC

4.50 ±0.10

6.60 ±0.10

1.05 ±0.10

3.86(.152)

MILLIMETERS(INCHES) *DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH

SHALL NOT EXCEED 0.150mm (.006") PER SIDE

NOTE:1. CONTROLLING DIMENSION: MILLIMETERS

2. DIMENSIONS ARE IN

3. DRAWING NOT TO SCALE

SEE NOTE 4

4. RECOMMENDED MINIMUM PCB METAL SIZE FOR EXPOSED PAD ATTACHMENT

6.40(.252)BSC

FE Package20-Lead Plastic TSSOP (4.4mm)

(Reference LTC DWG # 05-08-1663 Rev K)Exposed Pad Variation CB

DETAIL A

0.60(.024)REF0.28

(.011)REF


http://www.linear.com/designtools/packaging/

LT5503

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Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa-tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.

revision hisToryREV DATE DESCRIPTION PAGE NUMBER

A 10/15 Obsolete Product 1, 2


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For more information www.linear.com/LT5503 LINEAR TECHNOLOGY CORPORATION 2001

LT 1015 REV A • PRINTED IN USALinear Technology Corporation1630 McCarthy Blvd., Milpitas, CA 95035-7417(408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com/LT5503

relaTeD parTsPART NUMBER DESCRIPTION COMMENTS

LT5500 RF Front End Dual LNA Gain Setting +13.5dB/–14dB at 2.5GHz, Double-Balanced Mixer, 1.8V ≤ VSUPPLY ≤ 5.25V

LT5502 400MHz Quadrature Demodulator with RSSI 1.8V to 5.25V Supply, 70MHz to 400MHz IF, 84dB Limiting Gain, 90dB RSSI Range

LT5504 800MHz to 2.7GHz RF Measuring Receiver 80dB Dynamic Range, Temperature Compensated, 2.7V to 5.5V Supply

LTC5505 300MHz to 3.5GHz RF Power Detector >40dB Dynamic Range, Temperature Compensated, 2.7V to 6V Supply

LT5506 500MHz Quadrature IF Demodulator with VGA 1.8V to 5.25V Supply, 40MHz to 500MHz IF, –4dB to 57dB Linear Power Gain

LTC®5507 100kHz to 1GHz RF Power Detector 48dB Dynamic Range, Temperature Compensated, 2.7V to 6V Supply

LTC5508 300MHz to 7GHz RF Power Detector SC70 Package

LTC5509 300MHz to 3GHz RF Power Detector 36dB Dynamic Range, SC70 Package

LT5511 High Signal Level Up Converting Mixer RF Output to 3GHz, 17dBm IIP3, Integrated LO Buffer

LT5512 High Signal Level Down Converting Mixer DC-3GHz, 20dBm IIP3, Integrated LO Buffer

LT5515 1.5GHz to 2.5GHz Direct Conversion Demodulator 20dBm IIP3, Integrated LO Quadrature Generator

LT5516 0.8GHz to 1.5GHz Direct Conversion Quadrature Demodulator

21.5dBm IIP3, Integrated LO Quadrature Generator

LT5522 600MHz to 2.7GHz High Signal Level Mixer 25dBm IIP3 at 900MHz, 21.5dBm IIP3 at 1.9GHz, Matched 50Ω RF and LO Ports, Integrated LO Buffer

LTC5532 300MHz to 7GHz Precision RF Power Detector Precision VOUT Offset Control, Adjustable Gain and Offset Voltage






http://www.linear.com/LTC5505











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