Voltage Monitoring Supervisory Circuits ADM706P/R/S/T, ADM708R/S/T

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Voltage Monitoring Supervisory Circuits ADM706P/R/S/T, ADM708R/S/T

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FEATURES Precision Supply-Voltage Monitor +2.63 (ADM706P/R, ADM708R) +2.93 (ADM706S, ADM708S) +3.08 (ADM706T, ADM708T) Quiescent Current Reset Pulsewidth Debounced Manual Reset Input (MR) Independent Watchdog Timer-1.6 Timeout (ADM706x) Reset Output Active High (ADM706P) Active (ADM706R/S/T) Both Active High Active (ADM708R/S/T) Voltage Monitor Power-Fail Battery Warning Guaranteed RESET Valid with Superior Upgrade MAX706P/R/S/T, MAX708R/S/T APPLICATIONS Microprocessor Systems Computers Controllers Intelligent Instruments Critical Monitoring Automotive Systems Battery Operated Systems Portable Instruments GENERAL DESCRIPTION
Voltage Monitoring Supervisory Circuits ADM706P/R/S/T, ADM708R/S/T
WATCHDOG INPUT (WDI) WATCHDOG TRANSITION DETECTOR WATCHDOG TIMER WATCHDOG OUTPUT(WDO)
RESET WATCHDOG TIMEBASE
RESET GENERATOR
RESET, RESET)
VREF*
ADM706
POWER FAIL INPUT (PFI) 1.25V POWER FAIL OUTPUT (PFO)
*VOLTAGE REFERENCE 2.63V (P/R), 2.93V (S), 3.08V
RESET RESET GENERATOR RESET
VREF* POWER FAIL INPUT (PFI) 1.25V
ADM708
POWER FAIL OUTPUT (PFO)
ADM706P/R/S/T ADM708R/S/T microprocessor supervisory circuits suitable monitoring either power supplies. ADM706P/R/S/T provide following functions: Power-supply monitoring circuitry which generates Reset output during power-up, power-down brownout conditions. reset output remains operational with Independent watchdog monitoring circuitry which activated watchdog input been toggled within seconds. 1.25 threshold detector power fail warning, battery detection, monitor additional power supply. active debounced manual reset input (MR). ADM706R, ADM706S, ADM706T identical except reset threshold monitor levels which 2.63 2.93 3.08 respectively. ADM706P identical ADM706R that reset threshold 2.63 differs only that active high reset output. REV.
Information furnished Analog Devices believed accurate reliable. However, responsibility assumed Analog Devices use, infringements patents other rights third parties which result from use. license granted implication otherwise under patent patent rights Analog Devices.
*VOLTAGE REFERENCE 2.63V (R), 2.93V (S), 3.08V
ADM708R/S/T provide same functionality ADM706R/S/T only differ that: watchdog timer function available. active high reset output (RESET) addition active (RESET) output available. parts available 8-lead narrow SOIC packages.
Technology Way, P.O. 9106, Norwood, 02062-9106, U.S.A. Tel: 781/329-4700 World Wide Site: http://www.analog.com Fax: 781/326-8703 Analog Devices, Inc., 1999
ADM706P/R/S/T, ADM708R/S/T-SPECIFICATIONS
3.00 (ADM70_S), 3.15 (ADM70_T), TMIN TMAX unless otherwise noted.)
Parameter Operating Voltage Range Supply Current Reset Threshold (VRST) Reset Threshold Hysteresis Reset Pulsewidth 2.55 2.85 3.00 2.63 2.93 3.08 2.70 3.00 3.15 Units
2.70 (ADM70_P/R),
Test Conditions/Comments ADM70_P/R ADM70_S ADM70_T ADM70_P/R, ADM70_S/T, ADM70_R/S/T VRST (max) ISOURCE VRST (max) ISINK ISOURCE ISINK ISINK ADM706P VRST (max) ISOURCE VRST (max) ISINK ISOURCE ISINK ADM708_ VRST (max) ISOURCE VRST (max) ISINK ISOURCE ISINK ADM70_P/R; ADM70_S/T, (VCC) (0.8) VRST (max) ADM706_ VRST (max) VRST (max) VRST (max) ISOURCE VRST (max) ISINK ISOURCE ISINK VRST (max) VRST (max) VRST (max) VRST (max)
RESET Output Voltage RESET Output Voltage RESET Output Voltage Watchdog Timeout Period Pulsewidth
VCC-1.5 VCC-0.6 VCC-1.5 VCC-1.5 1.00 1.60 2.25
Input Threshold Input Current Output Voltage Pull Current Pulsewidth Input Threshold -1.0 VCC-1.5 0.02
REV.
ADM706P/R/S/T, ADM708R/S/T
Parameter Reset Output Delay Input Threshold Input Current Output Voltage VCC-1.5 1.25 0.01 Units VRST (max) ISOURCE VRST (max) ISINK ISOURCE ISINK Test Conditions/Comments VRST (max) ADM70_P/R; ADM70_S/T, falling
ORDERING GUIDE
ABSOLUTE MAXIMUM RATINGS*
+25°C unless otherwise noted)
Model ADM706PAN ADM706PAR ADM706RAN ADM706RAR ADM706SAN ADM706SAR ADM706TAN ADM706TAR ADM708RAN ADM708RAR ADM708SAN ADM708SAR ADM708TAN ADM708TAR
Temperature 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 -40°C +85°C -40°C +85°C -40°C +85°C -40°C +85°C -40°C +85°C -40°C +85°C -40°C +85°C -40°C +85°C
Package Options SO-8 SO-8 SO-8 SO-8 SO-8 SO-8 SO-8
-0.3 Other Inputs -0.3 Input Current Digital Output Current Power Dissipation, Thermal Impedance 135°C/W Power Dissipation, SO-8 SOIC Thermal Impedance 110°C/W Operating Temperature Range Industrial Version) -40°C +85°C Lead Temperature (Soldering, secs) +300°C Vapor Phase secs) +215°C Infrared secs) +220°C Storage Temperature Range -65°C +150°C Rating
*Stresses above those listed under Absolute Maximum Ratings cause permanent damage device. This stress rating only; functional operation device these other conditions above those listed operational sections this specification implied. Exposure absolute maximum ratings extended periods time affect device reliability.
REV.
ADM706P/R/S/T, ADM708R/S/T
FUNCTION DESCRIPTIONS
Mnemonic
ADM706
ADM708
Function Manual Reset Input. When taken below RESET generated. driven from TTL, CMOS logic from manual reset switch internally debounced. internal pull-up current holds input high when floating. Power Supply Input. Ground reference signals. Power Fail Input. noninverting input Power Fail Comparator. When less than 1.25 goes low. unused, should connected GND. Power Fail Output. output from Power Fail Comparator. goes when less than 1.25 Watchdog Input. three level input. remains either high longer than watchdog timeout period, watchdog output goes low. timer resets with each transition input. Either high-to-low low-to-high transition will clear counter. internal timer also cleared whenever reset asserted. Watchdog Timer disabled when left floating connected three-state buffer. Connect. Logic Output. RESET goes when triggered. triggered either being below reset threshold signal manual reset (MR) input. RESET will remain whenever below reset threshold. remains after goes above reset threshold goes from high. watchdog timeout will trigger RESET unless connected Logic Output. RESET active high output suitable systems which active high RESET logic. inverse RESET. Logic Output. Watchdog Output, WDO, goes internal watchdog timer times result inactivity input. remains until watchdog timer cleared. also goes during line conditions. Whenever below reset threshold, remains low. soon goes above reset threshold, goes high immediately.
CONFIGURATIONS
RESET
(R/S/T Only)
RESET
Only)
RESET
ADM706
RESET
ADM706 R/S/T
RESET
ADM708 R/S/T
RESET
VIEW (Not Scale)
VIEW (Not Scale)
VIEW (Not Scale)
CONNECT
REV.
ADM706P/R/S/T, ADM708R/S/T
Manual Reset
WATCHDOG INPUT (WDI) WATCHDOG TRANSITION DETECTOR WATCHDOG TIMER WATCHDOG OUTPUT(WDO)
RESET WATCHDOG TIMEBASE
manual reset input (MR) allows other reset sources such manual reset switch generate processor reset. input effectively debounced timeout period (200 typical). input TTL/CMOS compatible also driven logic reset output. unused, input tied high left floating.
RESET GENERATOR
RESET, RESET)
VREF* RESET
ADM706
POWER FAIL INPUT (PFI) 1.25V POWER FAIL OUTPUT (PFO) EXTERNALLY DRIVEN
*VOLTAGE REFERENCE 2.63V (P/R), 2.93V (S), 3.08V
Figure ADM706 Functional Block Diagram
RESET RESET GENERATOR RESET
NOTE: RESET COMPLEMENT RESET
Figure RESET, Timing
Watchdog Timer (ADM706)
VREF* POWER FAIL INPUT (PFI) 1.25V
ADM708
POWER FAIL OUTPUT (PFO)
*VOLTAGE REFERENCE 2.63V (R), 2.93V (S), 3.08V
Figure ADM708 Functional Block Diagram
CIRCUIT INFORMATION Power Fail Reset
watchdog timer circuit used monitor activity microprocessor order check that stalled indefinite loop. output line processor used toggle Watchdog Input (WDI) line. this line toggled within timeout period (1.6 sec), watchdog output (WDO) driven low. output connected nonmaskable interrupt (NMI) processor. Therefore, watchdog timer times out, interrupt generated. interrupt service routine should then used rectify problem. watchdog timer cleared either high-to-low low-to-high transition WDI. Pulses narrow detected. timer also cleared RESET/RESET going active. Therefore watchdog timeout period begins after reset goes inactive. When falls below reset threshold, forced whether watchdog timer timed out. Normally this would generate interrupt overridden RESET/ RESET going active. watchdog monitor deactivated floating Watchdog Input (WDI). output used line output since will only when falls below reset threshold.
reset output provides reset (RESET RESET) output signal Microprocessor whenever input below reset threshold. actual reset threshold voltage dependent whether P/R, suffix device used. internal timer holds reset output active after voltage rises above threshold. This intended power-on reset signal microprocessor. allows time both power supply microprocessor stabilize after powerup. power supply brownout interruption occurs, reset line similarly activated remains active after supply recovers. another interruption occurs during active reset period, then reset timeout period continues additional reset output guaranteed remain valid with This ensures that microprocessor held stable shutdown condition power supply starts ADM706P provides active high reset (RESET) signal; ADM706R/S/T provides active (RESET) signal; while ADM708R/S/T provides both RESET RESET.
RESET
RESET EXTERNALLY TRIGGERED
Figure Watchdog Timing
REV.
ADM706P/R/S/T, ADM708R/S/T
Power-Fail Comparator
power-fail comparator independent comparator which used monitor input power supply. comparator's inverting input internally connected 1.25 reference voltage. noninverting input available input. This input used monitor input power supply resistive divider network. When voltage input drops below 1.25 comparator output (PFO) goes indicating power failure. early warning power failure comparator used monitor preregulator input simply choosing appropriate resistive divider network. output used interrupt processor that shutdown procedure implemented before power lost.
INPUT POWER
1.25 1.25 1.25 1.25
Valid RESET Below
ADM70x family products guaranteed provide valid reset level with Please refer Typical Performance Characteristics. drops below internal transistor will have sufficient drive hold voltage RESET will longer held pulldown resistor shown Figure connected externally hold line required.
1.25V
POWER-FAIL OUTPUT
ADM70x
RESET
POWER-FAIL INPUT
ADM70x
Figure Power-Fail Comparator
Adding Hysteresis Power-Fail Comparator
Figure RESET Valid Below
increased noise immunity, hysteresis added power-fail comparator. Since comparator circuit noninverting, hysteresis added simply connecting resistor between output input shown Figure When low, resistor sinks current from summing junction pin. When high, resistor sources current into summing junction. This results differing trip levels comparator. Further noise immunity achieved connecting capacitor between GND.
ADM663A INPUT POWER 1.25V +3.3V
Typical Performance Characteristics
RESET
ADM70x
400ms/DIV
Figure ADM706/ADM708 RESET Output Voltage Supply Voltage
3.3V
Figure Adding Hysteresis Power-Fail Comparator
1.25
RESET
400ms/DIV
Figure RESET Output Voltage Supply Voltage
REV.
ADM706P/R/S/T, ADM708R/S/T
1.3V +1.2V RESET RESET
500ns/DIV
100ns/DIV
Figure Assertion Response Time
Figure RESET, RESET Deassertion
+1.3V
1.2V RESET
500ns/DIV
s/DIV
Figure Deassertion Response Time
Figure ADM706/ADM708 RESET Response Time
APPLICATIONS
RESET RESET
typical operating Circuit shown Figure unregulated input supply monitored using input resistive divider network. Resistors should selected such that when supply voltage drops below desired level (e.g., voltage drops below 1.25 threshold thereby generating interrupt Monitoring preregulator input gives additional time execute orderly shutdown procedure before power lost.
ADM666A
+3.3V
UNREGULATED 100ns/DIV
Figure RESET, RESET Assertion
RESET
RESET LINE
ADM706
MANUAL RESET
INTERRUPT
Figure Typical Application Circuit
REV.
ADM706P/R/S/T, ADM708R/S/T
Microprocessor activity monitored using input. This driven using output line from processor. software routines should toggle this line least once every seconds. problem occurs this line toggled, then goes nonmaskable interrupt generated. This interrupt routine used clear problem. event inactivity line, system reset required, then output should connected input shown Figure
RESET RESET +3V/+3.3V RESET RESET
ADM706
Figure Monitoring V/3.3 Additional Supply,
ADM706
LINE
with Bidirectional RESET
Figure RESET from
Monitoring Additional Supply Levels
order prevent contention microprocessors with bidirectional reset line, current limiting resistor should inserted between ADM70x RESET output reset pin. This will limit current safe level there conflicting output reset levels. suitable resistor value reset output required other uses, then should buffered shown Figure
+3V/+3.3V BUFFERED RESET
possible power-fail comparator monitor second supply shown Figure sensing resistors selected such that voltage drops below 1.25 minimum acceptable input supply. output connected input that RESET generated when supply drops tolerance. this case either supply drops tolerance, RESET will generated.
ADM70x
RESET RESET
Figure Bidirectional RESET
OUTLINE DIMENSIONS
Dimensions shown inches (mm).
8-Lead Plastic (N-8)
0.430 (10.92) 0.348 (8.84)
8-Lead SOIC (SO-8)
0.1968 (5.00) 0.1890 (4.80)
0.280 (7.11) 0.240 (6.10) 0.325 (8.25) 0.300 (7.62) 0.060 (1.52) 0.015 (0.38) 0.130 (3.30) 0.015 (0.381) 0.008 (0.204) 0.195 (4.95) 0.115 (2.93)
0.1574 (4.00) 0.1497 (3.80)
0.2440 (6.20) 0.2284 (5.80)
0.100 (2.54)
0.160 (4.06) 0.115 (2.93)
SEATING PLANE
0.0192 (0.49) 0.0138 (0.35)
0.0098 (0.25) 0.0075 (0.19)
0.0500 (1.27) 0.0160 (0.41)
0.022 (0.558) 0.070 (1.77) SEATING 0.014 (0.356) 0.045 (1.15) PLANE
REV.
PRINTED U.S.A.
0.210 (5.33)
0.0500 (1.27) 0.0098 (0.25) 0.0040 (0.10) 0.0688 (1.75) 0.0532 (1.35)
0.0196 (0.50) 0.0099 (0.25)
C1998a-0-12/99

Voltage Monitoring Supervisory Circuits ADM706P/R/S/T, ADM708R/S/T

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