MICROPROCESSOR ( µP) SUPERVISORY Low Power Voltage Detector Hi-Flex Adjustable Delay Time Reset IC Single Voltage Monitor Product Guide Micro processors require a reset pulse during power-on to initialize the internal registers and prevent unwanted code execution. Without a reset, the device could attempt to run even when the clock oscillator or V CC has not stabilized, thereby causing unpredictable operation. Why use a Microprocessor Reset? The fundamental application of a MPS (Microprocessor Supervisory) circuit is to keep the microprocessor of a system under control. Thus a system with a good µP Supervisory circuit can greatly enhance the quality and reliability of the product. A Microprocessor R/C Circuit vs. Reset IC In many cases, designers use R/C Circuit to perform System Reset function in their applications. However, R/C circuit have inherent defects in its design. For example, it is not able to provide reliable reset signals when the supply voltage fluctuates below the threshold voltage. It can also cause unpredictable system behaviors, for example, if the system is power cycled in short intervals, the capacitor can not completely discharge and, the circuit may not generate a reliable reset signal. If the system designer uses a Reset IC in their system, the IC can reliably generate a reset signal even if the supply voltage fluctuates below the threshold voltage, and additionally, if the system is powered cycled in short intervals. The Reset IC ensures that reliable reset signals are generated to guarantee reliable system power-up. Voltage Time Power Supply Microprocessor in Unknown state Power-on without reset Voltage Time RESET Power Supply Microprocessor initializes Correctly Power-on with reset Keep Your µP Under Control During Power-On Microprocessor Supervisory IC USB Power Switch Microprocessor Supervisory IC Microprocessor Supervisory IC Microprocessor Reset ........................... 1 Fixed Delay Time Reset IC .................... 2 Adjustable Delay Time Reset IC ............ 3 Watchdog Timers................................. 4 Contents Single Voltage Monitors ....................... 5 Multi-Voltage Monitors......................... 6 Selector Guide ................................. 7-9 Product Guide ..................................... 9 Microprocessor Reset ICs
10
Embed
Microprocessor Keep Your µP Under Control During Power-On … · 2015-04-17 · MICROPROCESSOR (®µ P) SUPERVISORY Low Power Hi-Flex Adjustable Delay Voltage Detector Time Reset
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
®MIC
RO
PR
OC
ESSO
R (
µP)
SUP
ERV
ISO
RY
Low PowerVoltage DetectorHi-Flex Adjustable Delay
Time Reset ICSingle
Voltage Monitor
®
Prod
uct G
uide
Micro processors require a reset pulse during power-on to initialize the internal registers and prevent unwanted code execution. Without a reset, the device could attempt to run even when the clock oscillator or VCC has not stabilized, thereby causing unpredictable operation.
Why use a Microprocessor Reset?The fundamental application of a MPS (Microprocessor Supervisory) circuit is to keep the microprocessor of a system under control. Thus a system with a good µP Supervisory circuit can greatly enhance the quality and reliability of the product.
A Microprocessor R/C Circuit vs. Reset ICIn many cases, designers use R/C Circuit to perform System Reset function in their applications. However, R/C circuit have inherent defects in its design. For example, it is not able to provide reliable reset signals when the supply voltage fluctuates below the threshold voltage. It can also cause unpredictable system behaviors, for example, if the system is power cycled in short intervals, the capacitor can not completely discharge and, the circuit may not generate a reliable reset signal.
If the system designer uses a Reset IC in their system, the IC can reliably generate a reset signal even if the supply voltage fluctuates below the threshold voltage, and additionally, if the system is powered cycled in short intervals. The Reset IC ensures that reliable reset signals are generated to guarantee reliable system power-up.
Volta
ge
Time
Power Supply
Microprocessor in Unknown state
Power-on without reset
Volta
ge
Time
RESET
Power Supply
Microprocessor initializes Correctly
Power-on with reset
Keep Your µP Under Control During Power-OnMicroprocessorSupervisory IC
All trademarks are property of their respective owners
Fixed Delay Time Reset ICsPericom’s Reset ICs families provide fixed delay time function. They can be used as delayed timing devices with delay settings in 200ms, 1570ms, 1.4ms, 1.5ms, 30ms, 26ms, 0.07ms and 1680ms etc. The Reset ICs families with Fixed Delay Time are listed in the table below.
Comparison of R/C Circuit and Reset IC Functionality
threshold
CPU
/RST
VDD
VCC
RC Reset
/RST
VCC
What are μP Supervisory Functions ?Pericom’s Supervisory ICs integrate functions such as a Manual-Reset (MR) input, Watchdog Timer, and Fixed Delay Timer or Adjustable Delay Timer. Devices such as, PT7M6118-6150 and PT7M6418-6450, provide ultra -small, 1.6mm x 1.6mm, DFN packages. These Reset ICs are perfect matches for applications with limited board space.
Hi-Flex Adjustable Delay Time Reset ICsPericom’s Hi-Flex Adjustable Reset IC families provide adjustable delay time function. These can be used in applications that require variable delay time. Some designs may require 2s delay time in one case and 0.x ms delay time in another. Our Adjustable Delay Time Reset ICs provide adjustable delay time setting with the flexibility for customer’s application.
Connect an external capacitor (CCdelay ) from Cd to GND delay period.
tdelay=Cd×4×106+40μs
There is a fixed short delay (40µs, typ) for the output deasserting when Vin falls below Vth.
PT7M65xx Features
ÎÎ Operates from VCC of 1.2V to 5.5V
ÎÎ Capacitor-Adjustable Delay
ÎÎ Active-High/-Low Output Options
ÎÎ Open-Drain /Push-Pull Output Options
ÎÎ Low Supply Current (2µA, Typ.)
ÎÎ Operating Temperature Range: -40°C to +85°C
ÎÎ Ultra-Small 4-Pin DFN Package or SOT23 Package or SC70-4 package
Microprocessor
Input
Reset Output Reset
Rup
GNDGND
3
2
1
4VDD
VDD
CDCDPT7M65xxNL
Series
3
®
PT7A75xx: Watchdog TimersMany microprocessors integrate a watchdog timer as a low cost means for ensuring that the processor executes within proper code boundaries. However, the watchdog operates from the same supply voltage and clock inputs as the processor, it is often subject to the same transient errors. These designs are also vulnerable to software errors such as runaway code, which can disable the built-in timer.
Designers should use an external watchdog timer to guarantee proper inputs to the processor each and every time. Pericom’s PT7A75xx series can offer µP Supervisors IC with watchdog function and Manual Reset function.
PT7A75xx FeaturesThe PT7A751X/752X/753X family of microprocessor (µP) Supervisory circuits are targeted to improve reliability and accuracy of power-supply circuitry in µP’s systems. These devices reduce the complexity and number of components required to monitor power-supply and battery functions.
Application Circuit: Networking Segment/Digital Media Application.
DSP
PT7M3808G12 PT7M3808G33
1.2V 3.3V
GPIO
GND
VIO VCORESENSE
RESET
GNDCT
VDD SENSE
GND
MRRESET
VDD
CT
Selecting the RESET Delay TimeThe PT7M3808 has three options for setting the RESET delay time:
1. A fixed 300ms typical delay time by tying CT to VDD through a resistor from 40kΩ to 200kΩ.
2. A fixed 20ms delay time by leaving the CT pin open.
3. A ground referenced capacitor connected to CT for a user-defined program time between 1.25ms and 10s. The capacitor CT should be ≥ 100pF nominal value in order for the PT7M3808xxx to recognize that the capacitor is present. The capacitor value for a given delay time can be calculated using the following equation:
(xx) refers to voltage range, 1.8V to 5.0V. For example, PT7M6418, thres- hold voltage is1.8V.
PT7M64xxCH# - - √ - - 200ms
PT7M64xxNL# - √ - - - 200ms
µP SUPERVISORY PRODUCT SELECTION GUIDEPericom offers a diverse range of accurate, low cost µP Supervisory solutions for handheld & embedded applications
CONTINUED.. 7
®
µP SUPERVISORY PRODUCT SELECTION GUIDE (cont..)SINGLE VOLTAGE MONITOR (No Delay Time)
PT7M6709AU 5 3.3 2.5 Adj* 10 MSOP-10 *Adjustable voltage based on 0.62V internal threshold. External threshold voltage can be set using an external resistor-divider.
PT7M6709BU 5 3.3 2.5 Adj* 5 MSOP-10
PT7M6709CU 5 3.3 1.8 Adj* 10 MSOP-10
PT7M6709DU 5 3.3 1.8 Adj* 5 MSOP-10
PT7M6709EU Adj* 3.3 2.5 1.8 10 MSOP-10
PT7M6709FU Adj* 3.3 2.5 1.8 5 MSOP-10
PT7M6709GU 5 3.3 Adj* Adj* 10 MSOP-10
PT7M6709HU 5 3.3 Adj* Adj* 5 MSOP-10
PT7M6709IU Adj* 3.3 2.5 Adj* 10 MSOP-10
PT7M6709JU Adj* 3.3 2.5 Adj* 5 MSOP-10
PT7M6709KU Adj* 3.3 1.8 Adj* 10 MSOP-10
PT7M6709LU Adj* 3.3 1.8 Adj* 5 MSOP-10
PT7M6709MU Adj* 3 Adj* Adj* 10 MSOP-10
PT7M6709NU Adj* 3 Adj* Adj* 5 MSOP-10
PT7M6709OU Adj* Adj* Adj* Adj* N/A MSOP-10
8
®
MULTI-VOLTAGE MONITOR (Quad Voltage)
Part Number Nominal Input VoltageSupply Tolerance(%) Package Remark
PT7M6832-PT7M6837: (x) refers to voltage range, W:1.665v, V:1.575v, I:1.388v, H:1.313v, G:1.11v, F:1.050v PT7M6838-PT7M6840: Adjustable voltage based on 0.444V internal threshold
PT7M6835xDx# - - - √
PT7M6838Dx# - - - √
PT7M6833xDx# - - √ -
PT7M6836xDx# - - √ -
PT7M6839Dx# - - √ -
PT7M6834xDx# - √ - -
PT7M6837xDx# - √ - -
PT7M6840Dx# - √ - -
SINGLE VOLTAGE MONITOR (with 4 Fixed Different Delay Time)
Part Number Reset Output
Reset Time Package RemarkOpen-Drain Push-Pull
Active high Active low Active high Active low
PT7M6314USxxDx# - √ - - Suffix Dx refers to Reset Time D1:1.4ms,D2:26ms D3:200ms,D4:1570ms
#=TB:SOT143-4 (xx) refers to voltage range, 2.5V to 5.0V. For example, PT7M6315US25, threshold voltage is 2.5V.