Pin-Selectable Watchdog Timers MAX6369-MAX6374 pin-selectable wat

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Pin-Selectable Watchdog Timers MAX6369-MAX6374 pin-selectable wat

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19-1676; 2/03
Pin-Selectable Watchdog Timers
MAX6369-MAX6374 pin-selectable watchdog timers that supervise microprocessor (µP) activity signal when system operating improperly. During normal operation, microprocessor should repeatedly toggle watchdog input (WDI) before selected watchdog timeout period elapses demonstrate that system processing code properly. does provide valid watchdog input transition before timeout period expires, supervisor asserts watchdog (WDO) output signal that system executing desired instructions within expected time frame. watchdog output pulse used reset interrupt system warn processing errors. MAX6369-MAX6374 flexible watchdog timer supervisors that increase system reliability through notification code execution errors. family offers several pin-selectable watchdog timing options match wide range system timing applications: Watchdog startup delay: provides initial delay before watchdog timer started. Watchdog timeout period: normal operating watchdog timeout period after initial startup delay. Watchdog output/timing options: open drain (100ms) push-pull (1ms). MAX6369-MAX6374 operate over +2.5V +5.5V supply range available miniature 8-pin SOT23 packages.
Features
Precision Watchdog Timer Critical Applications Pin-Selectable Watchdog Timeout Periods Pin-Selectable Watchdog Startup Delay Periods Ability Change Watchdog Timing Characteristics Without Power Cycling Open-Drain Push-Pull Pulsed Active-Low Watchdog Output Watchdog Timer Disable Feature +2.5V +5.5V Operating Voltage Supply Current External Components Required Miniature 8-Pin SOT23 Package
MAX6369-MAX6374
Ordering Information
PART MAX6369KA-T MAX6370KA-T MAX6371KA-T MAX6372KA-T MAX6373KA-T MAX6374KA-T TEMP RANGE -40°C +85°C -40°C +85°C -40°C +85°C -40°C +85°C -40°C +85°C -40°C +85°C PINPACKAGE SOT23-8 SOT23-8 SOT23-8 SOT23-8 SOT23-8 SOT23-8 MARKS AADC AADD AADE AADF AADG AADH
_Applications
Embedded Control Systems Industrial Controllers Critical Microcontroller (µC) Monitoring Automotive Telecommunications Networking
Note: devices available tape-and-reel only. Required order increment 2,500 pieces.
Configuration appears data sheet.
Selector Guide
PART MAX6369 MAX6370 MAX6371 MAX6372 MAX6373 MAX6374 OUTPUT Open Drain Push-Pull Open Drain Push-Pull Open Drain Push-Pull PULSE WIDTH (ms) MINIMUM STARTUP DELAY Selectable: Selectable: Selectable: 200µs first edge Selectable: 200µs first edge MINIMUM WATCHDOG TIMEOUT Selectable: Selectable: Selectable: Selectable: Selectable: 30µs Selectable: 30µs
Maxim Integrated Products
pricing, delivery, ordering information, please contact Maxim/Dallas Direct! 1-888-629-4642, visit Maxim's website www.maxim-ic.com.
Pin-Selectable Watchdog Timers MAX6369-MAX6374
ABSOLUTE MAXIMUM RATINGS
Terminal Voltage (with respect GND) .-0.3V WDI.-0.3V (Open Drain: MAX6369/71/73) .-0.3V (Push-Pull: MAX6370/72/74 .-0.3V (VCC 0.3V) SET0, SET1, SET2 .-0.3V (VCC 0.3V) Maximum Current, (input/output).20mA Continuous Power Dissipation +70°C) SOT23-8 (derate 8.75mW/°C above +70°C).700mW Operating Temperature Range .-40°C +85°C Storage Temperature Range .-65°C +150°C Junction Temperature .+150°C Lead Temperature (soldering, 10s) .+300°C Rise Fall Rate.0.05V/µs
Stresses beyond those listed under "Absolute Maximum Ratings" cause permanent damage device. These stress ratings only, functional operation device these other conditions beyond those indicated operational sections specifications implied. Exposure absolute maximum rating conditions extended periods affect device reliability.
ELECTRICAL CHARACTERISTICS
(VCC +2.5V +5.5V, SET_ GND, -40°C +85°C, unless otherwise noted. Typical values +25°C +3V.) (Note
PARAMETER Operating Voltage Range Supply Current Input High Voltage Input Voltage Logic Input Current (Note Output Voltage SYMBOL load WDI, SET0, SET1, SET2 WDI, SET0, SET1, SET2 SET_ ISINK 1.2mA, 2.7V, watchdog output asserted ISINK 6mA, 4.5V, watchdog output asserted +5.5V, output deasserted, MAX6369/MAX6371/MAX6373 ISOURCE 500µA, 2.7V, watchdog output deasserted ISOURCE 800µA, 4.5V, watchdog output deasserted SET2 SET1 SET0 SET2 SET1 SET0 SET2 SET1 VCC, SET0 SET2 SET1 VCC, SET0 Startup Delay Period tDELAY SET2 VCC, SET1 SET0 SET2 VCC, SET1 SET0 SET2 VCC, SET1 VCC, SET0 SET2 VCC, SET1 VCC, SET0 3.3V 2.5V CONDITIONS UNITS
Leakage Current
ILKG
Output High Voltage MAX6369/MAX6370
Watchdog Disabled
Pin-Selectable Watchdog Timers
ELECTRICAL CHARACTERISTICS (continued)
(VCC +2.5V +5.5V, SET_ GND, -40°C +85°C, unless otherwise noted. Typical values +25°C +3V.) (Note
PARAMETER SYMBOL CONDITIONS SET2 SET1 SET0 SET2 SET1 SET0 SET2 SET1 VCC, SET0 Watchdog Timeout Period SET2 SET1 VCC, SET0 SET2 VCC, SET1 SET0 SET2 VCC, SET1 SET0 SET2 VCC, SET1 VCC, SET0 SET2 VCC, SET1 VCC, SET0 MAX6371/MAX6372 Startup Delay Period tDELAY SET2 SET1 VCC, SET0 other SET_ conditions SET2 SET1 SET0 SET2 SET1 SET0 SET2 SET1 VCC, SET0 Watchdog Time-Out Period SET2 SET1 VCC, SET0 SET2 VCC, SET1 SET0 SET2 VCC, SET1 SET0 SET2 VCC, SET1 VCC, SET0 SET2 VCC, SET1 VCC, SET0 MAX6373/MAX6374 SET2 SET1 SET0 SET2 SET1 SET0 SET2 SET1 VCC, SET0 Startup Delay Period tDELAY SET2 SET1 VCC, SET0 SET2 VCC, SET1 SET0 SET2 VCC, SET1 SET0 SET2 VCC, SET1 VCC, SET0 SET2 VCC, SET1 VCC, SET0 SET2 SET1 SET0 SET2 SET1 SET0 SET2 SET1 VCC, SET0 Watchdog Timeout Period SET2 SET1 VCC, SET0 SET2 VCC, SET1 SET0 SET2 VCC, SET1 SET0 SET2 VCC, SET1 VCC, SET0 SET2 VCC, SET1 VCC, SET0 Watchdog Disabled UNITS
MAX6369-MAX6374
Watchdog Disabled
Watchdog Disabled
Watchdog Disabled First Edge (Note First Edge (Note
Watchdog Disabled
Pin-Selectable Watchdog Timers MAX6369-MAX6374
ELECTRICAL CHARACTERISTICS (continued)
(VCC +2.5V +5.5V, SET_ GND, -40°C +85°C, unless otherwise noted. Typical values +25°C +3V.) (Note
PARAMETER Watchdog Input Pulse Width (Note Watchdog Output Pulse Width Internal Setup Time (Note SYMBOL tWDI tWDO tSETUP CONDITIONS After deasserted MAX6369/MAX6371/MAX6373 MAX6370/MAX6372/MAX6374 After deasserted UNITS
Note Production tested +25°C. Guaranteed design over temperature limits. Note Guaranteed design. Note this setting watchdog timer inactive startup delay ends when sees first level transition. Selecting Device Timing more information. Note After power-up, setting change, there internal setup time during which ignored.
Typical Operating Characteristics
(Circuit Figure +25°C, unless otherwise noted.)
SUPPLY CURRENT TEMPERATURE
MAX6369/74-01
WATCHDOG TIMEOUT PERIOD TEMPERATURE
NORMALIZED WATCHDOG TIMEOUT PERIOD
MAX6369/74-02
1.003 1.002 1.001 1.000 0.999 0.998 0.997
SUPPLY CURRENT (µA) +5.5V
+2.5V
TEMPERATURE (°C)
TEMPERATURE (°C)
Pin-Selectable Watchdog Timers
Description
NAME N.C. SET0 SET1 SET2 FUNCTION Watchdog Input. remains either high duration watchdog timeout period (tWD), triggers pulse. internal watchdog timer clears whenever asserted whenever sees rising falling edge. Ground Connected. make connection this pin. Zero. Logic input selecting startup delay watchdog timeout periods. Table timing details. One. Logic input selecting startup delay watchdog timeout periods. Table timing details. Two. Logic input selecting startup delay watchdog timeout periods. Table timing details. Watchdog Output. Pulses watchdog output pulse width, tWDO, when internal watchdog times out. MAX6369/MAX6371/MAX6373 have open-drain outputs require pull-up resistor. MAX6370/MAX6372/MAX6374 outputs push-pull. Supply Voltage (+2.5V +5.5V)
MAX6369-MAX6374
Table Minimum Timeout Settings
LOGIC INPUTS SET2 SET1 SET0 MAX6369/MAX6370 tDELAY, 10ms 30ms Disabled 100ms MAX6371/MAX6372 tDELAY 60s, 10ms Disabled 100ms 300ms MAX6373/MAX6374 tDELAY Disabled 200µs First Edge First Edge Disabled 30µs
Detailed Description
MAX6369-MAX6374 flexible watchdog circuits monitoring activity. During normal operation, internal timer cleared each time toggles with valid logic transition (low high high low) within selected timeout period (tWD). remains high long input strobed within selected timeout period. input strobed before timeout period expires, watchdog output asserted watchdog output pulse width (tWDO). device type state three logic control pins (SET0, SET1, SET2) determine watchdog timing characteristics. three basic timing variations watchdog startup delay normal
watchdog timeout period summarized below (see Table timeout characteristics devices family): Watchdog Startup Delay: Provides initial delay before watchdog timer started. Allows time system power initialize before assuming responsibility normal watchdog timer updates. Includes several fixed pin-selectable startup delay options from 200µs 60s, option wait first watchdog input transition before starting watchdog timer.
Pin-Selectable Watchdog Timers MAX6369-MAX6374
MAX6369-MAX6374
TRANSITION DETECTOR
CONTROL LOGIC ENABLE
CLEAR WATCHDOG TIMEOUT STARTUP DELAY WATCHDOG TIMER CIRCUITRY OUTPUT
Figure Functional Diagram
tSETUP
tDELAY
TRANSITIONS IGNORED DURING SETUP DELAY. TRANSITION(S) IGNORED DURING STARTUP DELAY PERIOD. WATCHDOG TIMER STARTS AFTER STARTUP DELAY DEASSERTED. TRANSITION OCCURS BEFORE WATCHDOG TIMEOUT PERIOD. WATCHDOG TIMER CLEARS STARTS TIMER AGAIN. WATCHDOG TIMES OUT, ASSERTS. TRANSITIONS IGNORED WHEN ASSERTED. WATCHDOG TIMER STARTS AFTER DEASSERTS. tWDO
Figure Watchdog Timing
Watchdog Timeout Period: Normal operating watchdog timeout period after initial startup delay. watchdog output pulse asserted valid watchdog input transition received before timeout period elapses. Eight pin-selectable timeout period options each device, from 30µs 60s. Pin-selectable watchdog timer disable feature.
Watchdog Output/Timing Options: Open drain, active with 100ms minimum watchdog output pulse (MAX6369/MAX6371/MAX6373). Push-pull, active with minimum watchdog output pulse (MAX6370/MAX6372/MAX6374). Each device watchdog startup delay that initiated when supervisor first powered after user modifies logic control inputs. watchdog timer does begin count down until
Pin-Selectable Watchdog Timers
completion startup delay period, watchdog output pulses asserted during startup delay. When startup delay expires, watchdog begins counting normal watchdog timeout period waiting transitions. startup delay allows time system power fully initialize before assuming responsibility normal watchdog timer updates. Startup delay periods vary between different devices altered logic control pins. ensure that system generates undesired watchdog outputs, routine watchdog input transitions should begin before selected minimum startup delay period expired. normal watchdog timeout period countdown initiated when startup delay complete. valid logic transition recognized before watchdog timeout period expired, supervisor asserts watchdog output. Watchdog timeout periods vary between different devices altered logic control pins. ensure that system generates undesired watchdog outputs, watchdog input transitions should occur before selected minimum watchdog timeout period expired. startup delay watchdog timeout period determined states SET0, SET1, SET2 pins, particular device within family. MAX6369 MAX6370, startup delay equal watchdog timeout period. startup watchdog timeout periods selectable from (minimum). MAX6371 MAX6372, startup delay fixed watchdog timeout period selectable from (minimum). MAX6373/MAX6374 provide timing variations startup delay normal watchdog timeout. Five pin-selectable modes provide startup delays from 200µs minimum, watchdog timeout delays from minimum. selectable modes initiate watchdog timer until device receives first valid watchdog input transition (there fixed period which first input must received). These extended startup delay modes useful applications requiring more than system initialization. MAX6369-MAX6374 devices disabled with proper logic control setting (Table
MAX6369-MAX6374
Applications Information
Input Signal Considerations
Watchdog timing measured from last rising falling edge associated with pulse least 100ns width. transitions ignored when asserted, during startup delay period (Figure Watchdog input transitions also ignored setup period, tSETUP, 300µs after power-up setting change (Figure
Selecting Device Timing
SET2, SET1, SET0 program startup delay watchdog timeout periods (Table Timeout settings hard wired, they controlled with logic gates modified during operation. ensure smooth transitions, system should strobe immediately before timing settings changed. This minimizes risk initializing setting change late timer countdown period generating undesired watchdog outputs. After changing timing settings, outcomes possible based WDO. change made while asserted, previous setting allowed finish, characteristics setting assumed, startup phase entered after 300µs setup time (tSETUP) elapses. change made while asserted, setting initiated immediately, startup phase entered after 300µs setup time elapses.
SET_ tSETUP *IGNORED EDGE tDELAY tSETUP tDELAY
Figure Setting Change Timing
Pin-Selectable Watchdog Timers MAX6369-MAX6374
register logic high while supplying input current leakage paths connected line. pullup sufficient most applications. MAX6370/ MAX6372/MAX6374 have push-pull outputs that provide active-low watchdog output pulse 1ms. When deasserts, timing begins again beginning watchdog timeout period (Figure
START
HIGH PROGRAM CODE
Usage Noisy Environments
using watchdog timer electrically noisy environment, bypass capacitor 0.1µF should connected between close device possible, further away than inches.
SUBROUTINE PROGRAM LOOP
POSSIBLE INFINITE LOOP PATH
_Watchdog Software Considerations
help watchdog timer monitor software execution more closely, reset watchdog input different points program, rather than pulsing watchdog input high-low-high low-high-low. This technique avoids stuck loop, which watchdog timer would continue reset inside loop, keeping watchdog from timing out. Figure shows example flow diagram where driving watchdog input high beginning program, every subroutine loop, then high again when program returns beginning. program should hang subroutine, problem would quickly corrected, since continually watchdog timer allowed time out, causing pulse.
RETURN
Figure Watchdog Flow Diagram
Selecting (SET2 SET1 SET0 disables watchdog timer function devices family. Operation reenabled without powering down changing inputs desired setting. device assumes selected timing characteristics enter startup phase after 300µs setup time elapses (Figure MAX6373/MAX6374 offer first-edge feature. first-edge mode (settings 110, Table internal timer does control startup delay period. Instead, startup terminates when sees transition. changing first-edge mode while device operating, disable mode must entered first. then safe select first-edge mode. Entering disable mode first ensures output unasserted when selecting firstedge mode removes danger being masked out.
Configuration
VIEW
N.C. SET2 SET1
Output
MAX6369/MAX6371/MAX6373 have active-low, open-drain output that provides watchdog output pulse 100ms. This output structure sinks current when asserted. Connect pullup resistor from supply voltage +5.5V. Select resistor value large enough register logic (see Electrical Characteristics), small enough
SET0
MAX6369 MAX6370 MAX6371 MAX6372 MAX6373 MAX6374 SOT23-8
Chip Information
TRANSISTOR COUNT: 1500 PROCESS: BiCMOS
Maxim cannot assume responsibility circuitry other than circuitry entirely embodied Maxim product. circuit patent licenses implied. Maxim reserves right change circuitry specifications without notice time.
_Maxim Integrated Products, Gabriel Drive, Sunnyvale, 94086 408-737-7600 2003 Maxim Integrated Products Printed registered trademark Maxim Integrated Products.

Pin-Selectable Watchdog Timers MAX6369-MAX6374 pin-selectable wat

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