Power Supply Supervisor With Battery Backup Switch ASM690A ASM692

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Power Supply Supervisor With Battery Backup Switch ASM690A ASM692

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ASM690A/692A ASM802L/802M ASM805L
Power Supply Supervisor With Battery Backup Switch
ASM690A ASM692A ASM802L ASM802M ASM805L offers complete single chip solutions power supply monitoring control battery functions microprocessor systems. Each device implements four functions: Reset control, watchdog monitoring, batterybackup switching powerfailure monitoring. addition microprocessor reset under power-up power-down conditions, these devices provide battery-backup switching maintain control power loss brown-out situations. Additional monitoring capabilities provide early warning unregulated power supply loss before voltage regulator drops out. important features these four functions are: second watchdog timer keep microprocessor responsive 4.40V 4.65V threshold microprocessor reset power-up power-down SPDT (Single-pole, Double-throw) PMOS switch connects backup power fails 1.25V threshold detector power loss general purpose voltage monitoring These features pin-compatible with industry standard power-supply supervisors. Short-circuit thermal protection have also been added. ASM690A ASM802L ASM805L generate reset pulse when supply voltage drops below 4.65V ASM692A ASM802M generate reset below 4.40V. ASM802L ASM802M have power-fail accuracy ASM805L same ASM690A except that RESET provided instead RESET.
Short circuit protection thermal limiting Small 8-pin 8-pin PDIP packages external components Specified over full temperature range
Applications
Embedded control systems Portable/Battery operated systems Intelligent instruments Wireless instruments Wireless communication systems PDAs hand-held equipments power supply monitoring Safety system
Typical Operating Circuit
Block Diagram
Features
precision supply-voltage monitor options 4.65V (ASM690A ASM802L ASM805L) 4.40V (ASM692A ASM802M Battery-backup power switch on-chip Watchdog timer: second timeout Power failure battery detection
PulseCore Semiconductor Corporation 1715 Bascom Suite Campbell, 95008 Tel: 408-879-9077 Fax: 408-879-9018 www.pulsecoresemi.com
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April 2008 Configuration
ASM690A/692A ASM802L/802M ASM805L
Description
Number ASM690A/ ASM692A ASM802L/ ASM802M Voltage supply RAM. When above reset threshold, VOUT connects through P-Channel device. falls below VOUT reset threshold, this output will connected backup supply VBATT VCC, whichever higher) through switch provide continuous power CMOS RAM. power supply input. Ground Power failure monitor input. connected internal power fail comparator which referenced 1.25V. power fail output (PFO) active remains HIGH above 1.25V. this feature unused, should connected VOUT. Power-fail output. active whenever less than 1.25V. Watchdog input. input monitors microprocessor activity. internal timer reset with each transition input. held HIGH longer than watchdog timeout period, typically seconds, RESET RESET) asserted reset pulse width time, tRS, 140ms, minimum. Active-LOW reset output. When triggered falling below reset threshold watchdog timer timeout, RESET pulses reset pulse width tRS, typically 200ms. will remain below reset RESET threshold (4.65V ASM690A ASM802L 4.4V ASM692A ASM802L) remains 200ms after rises above reset threshold. RESET VBATT Active-HIGH reset output. inverse RESET. Auxiliary power backup-battery input. VBATT should connected function used. input about 40mV hysteresis prevent rapid toggling between VBATT. ASM805L Name Function
Power Supply Supervisor With Battery Backup Switch
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April 2008 Detailed Description
important initialize microprocessor known state response specific events that could create code execution errors "lock-up". reset output these supervisory circuits send reset pulse microprocessor response power-up, powerdown/power-loss watchdog time-out. RESET/RESET Timing Power-up reset occurs when rising reaches reset threshold, VRT, forcing reset condition which reset output asserted appropriate logic state duration tRS. reset pulse width, tRS, typically around 200ms ASM690A, ASM692A, ASM802 HIGH ASM805L. Figure shows reset timing. Power-loss "brown-out" reset occurs when dips below reset threshold resulting reset assertion duration tRS. reset signal remains asserted long between 1.1V, lowest which thesedevices provide guaranteed logic-low output. ensure logic inputs connected ASM690A ASM692A/ASM802 RESET known state when under 1.1V, 100k pull-down resistor RESET needed: logic-high ASM805L will need pull-up resistor VCC. Watchdog Timer Watchdog time-out reset occurs when logic logic continuously applied more than seconds. After duration reset interval, watchdog timer starts second timing interval; microprocessor must service watchdog input changing states floating before this interval finished. held either HIGH LOW, reset pulse will triggered every seconds (the second timing interval plus reset pulse width tRS).
ASM690A/692A ASM802L/802M ASM805L
Application Information
Microprocessor Interface ASM690 logic-LOW RESET output while ASM805 inverted logic-HIGH RESET output. Microprocessors with bidirectional reset pins pose problem when supervisory circuit microprocessor output pins attempt opposite logic states. problem resolved placing 4.7k resistor between RESET output microprocessor reset pin. This shown Figure Since series resistor limits drive capabilities, reset signal other devices should buffered.
Power Supply Supervisor With Battery Backup Switch
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Watchdog Input discussed Reset section, Watchdog input used monitor microprocessor activity. used insure that microprocessor continually responsive state requiring that toggled every second. toggled within second window (minimum tRS), reset pulse will asserted return microprocessor initial start-up state. Pulses short 50ns applied pin. this feature used, should open circuited logic placed into highimpedance state allow float. Backup-Battery Switchover power loss made less severe system contents preserved. This achieved ASM690/692/ 802/805 switching from failed alternate power source connected VBATT when less than reset threshold voltage (VCC VRT), less than VBATT. VOUT normally connected through PMOS switch brown-out loss will cause switchover VBATT means PMOS switch. Although both conditions (VCC <VBATT) must occur switchover VBATT occur, VOUT will switched back when exceeds irrespective voltage VBATT. should noted that internal device diode Figure will forward biased VBATT exceeds more than diode drop when switched VOUT. Because this recommended that VBATT greater than +0.6V. Condition Reset Threshold Reset Threshold VBATT Reset Threshold VBATT SW1/SW2 Open Open Closed SW3/SW4 Closed Closed Open VOUT VBATT RESET
ASM690A/692A ASM802L/802M ASM805L
Table Connections Battery Backup Mode Connection Connected VBATT through internal PMOS switch Connected VOUT Disabled Logic-LOW Logic-LOW (except ASM805 where HIGH) Watchdog timer disabled
During backup power mode, internal circuitry supervisory circuit draws power from battery supply. While still alive, comparator circuits remain alive current drawn device typically 35µA. When drops more than 1.1V below VBATT, internal switchover comparator, comparator comparator will shut off, reducing quiescent current drawn less than 1µA. Backup Power Sources Batteries Battery voltage selection important insure that battery does discharge through parasitic device diode (see Figure when less than VBATT >VRT.
ASM690A/802A/805L Reset Threshold 4.65V ASM692A /ASM802M Reset Threshold 4.4V
Power Supply Supervisor With Battery Backup Switch
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ASM690A/692A ASM802L/802M ASM805L
ASM692A/802M within ±10%
Table Maximum Battery Voltages
ASM690A/802L/805L insure that storage capacitor does achieve over voltage state. Note: SuperCapis trademark Baknor Industries
Part Number ASM690A ASM802L ASM805L ASM692A ASM802M
MAXIMUM Battery Voltage 4.80 4.80 4.80 4.55 4.55
Although most batteries that meet requirements Table2 acceptable, lithium batteries very effective backup source their high-energy density very selfdischarge rates. Battery replacement while Powered Batteries replaced even when device powered state long remains above reset threshold voltage VRT. devices, floating VBATT will cause powersupply switchover occur some other supervisory circuits. VBATT used, should grounded. Backup Power Sources SuperCapCapacitor storage, with very high values capacitance, used back-up power source instead batteries. SuperCapare capacitors with capacities fractional farad range. farad SuperCapwould provide useful backup power source. Like battery supply, important that capacitor voltage remain below maximum voltages shown Table Although circuit Figure shows most simple connect SuperCapTM, this circuit cannot insure that over voltage condition will occur since capacitor will ultimately charge VCC. insure that over voltage condition does occur, circuit Figure preferred. this circuit configuration, diode-resistor pair clamps capacitor voltage diode drop below VCC. itself should regulated within Operation without Backup Power Source When operating without back-up power source, VBATT should connected VOUT should connected VCC, since power source switchover will occur. Connecting VOUT eliminates voltage drop ON-resistance PMOS switch.
Power Supply Supervisor With Battery Backup Switch
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Power-Fail Comparator Power Fail feature independent voltage monitoring function that used number monitoring activities. function provide early sensing power supply failure sensing voltage unregulated ahead regulated supply sensing seen backup-battery switchover circuitry. compared 1.25V internal reference. voltage less than this reference voltage, goes low. sensing voltage power supply, microprocessor system prepare imminent power-loss, especially battery backup supply enabled. input voltage results from simple resistor voltage divider shown Figure
ASM690A/692A ASM802L/802M ASM805L
reasonable should larger than avoid excessive loading pin. calculations correct values resistors hysteresis thresholds given Figure capacitor added offer additional noise rejection low-pass filtering.
Power Fail Hysteresis noise margin added simple monitoring circuit Figure adding positive feedback from pin. circuit Figure adds this positive "latching" effect means additional resistor connected between which helps pulling direction eliminating indecision trip point. Resistor normally about times higher resistance than keep hysteresis band Monitoring Capabilities Power-fail Input: Although designed power supply failure monitoring, used monitoring voltage condition that scaled means resistive divider. example negative power supply monitor configured Figure this case good negative supply will hold below 1.25V
Power Supply Supervisor With Battery Backup Switch
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will logic "0". negative voltage declines, voltage will rise until exceeds 1.25V will logic "1".
ASM690A/692A ASM802L/802M ASM805L
Power Supply Supervisor With Battery Backup Switch
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Absolute Maximum Ratings Parameter Terminal Voltage with Respect Ground
VBATT other inputs1 Input Current Input Current VBATT Input Current Output Current VOUT other inputs Rate Rise: VBATT Continuous Power Dissipation Plastic (derate 9mW/°C above 70°C) (derate 5.9mW/°C above 70°C) Operating Temperature Range Devices) Operating Temperature Range Devices) Storage Temperature Range Lead Temperature (Soldering, sec) -0.3 -0.3 -0.3
ASM690A/692A ASM802L/802M ASM805L
Unit
Short circuit protected V/µs
rating
input voltage limits exceeded current limited less than 10mA Note: These stress ratings only functional operation implied. Exposure absolute maximum ratings prolonged time periods affect device reliability.
Power Supply Supervisor With Battery Backup Switch
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April 2008 Electrical Characteristics
ASM690A/692A ASM802L/802M ASM805L
Unless other wise noted, 4.75V 5.5V ASM690A ASM802L ASM805L 4.5V 5.5V ASM692A ASM802M;VBATT 2.8V; TMIN TMAX.
Parameter
VCC, VBATT Voltage Range (Note Supply Current Excluding IOUT ISUPPLY Battery Backup Mode (Excluding IOUT) VBATT Standby Current (Note VOUT Output VOUT Battery Backup Mode Battery Switch Threshold, VBATT Battery Switch over Hysteresis Reset Threshold Reset Threshold Hysteresis Reset Pulse Width
SYMBOL
Conditions
Unit
25°C VBATT 2.8V =TMIN TMAX 5.5V>VCC>VBATT 0.2V IOUT IOUT 50mA IOUT=250µA, VBATT 0.2V Power Power Down 25°C =TMIN TMAX -0.1 -1.0 VCC-0.025 VCC-0.25 VBATT-
0.02 0.02 VCC0.010 VCC0.10 VBATT 0.001
4.75 4.50 4.70 4.45
ASM690A/802L/805L ASM692A, ASM802M ASM802L, 25°C, falling ASM802M, TA=25°C, falling
4.50 4.25 4.55 4.30
4.65 4.40
ISOURCE 800µA ISINK 3.2mA ASM805LC, ISOURCE=4µA, 1.1V ASM805LE, ISOURCE=4µA, 1.2V ASM805L, ISOURCE=800µA ASM805L, ISINK=3.2mA 0.4V, 0.8VCC Logic Logic HIGH
Reset Output Voltage
1.00 -150 1.60 2.25
Watchdog Timeout Pulse Width Input Current Input Threshold (Note
Power Supply Supervisor With Battery Backup Switch
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Parameter
Input Threshold Input Current Output Voltage ISOURCE 800µA ISINK 3.2mA
ASM690A/692A ASM802L/802M ASM805L
SYMBOL Conditions
ASM69_A, ASM805L, ASM802_C/E,
1.20 1.225
1.25 1.250 0.01
1.30 1.275
Unit
Notes: VBATT other must greater than 2.0V. Battery charging-current "-". Battery discharge current "+". guaranteed intermediate level state floating within operating voltage range. input impedance biased 0.3VCC.
Power Supply Supervisor With Battery Backup Switch
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April 2008 Package Dimensions 8-lead PDIP Package
ASM690A/692A ASM802L/802M ASM805L
Power Supply Supervisor With Battery Backup Switch
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April 2008 8-lead (150-mil) SOIC Package
ASM690A/692A ASM802L/802M ASM805L
Power Supply Supervisor With Battery Backup Switch
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April 2008 Ordering Information Lead Devices
Part Number
ASM690A ASM690ACPA ASM690ACSA ASM690AEPA ASM690AESA ASM692A ASM692ACPA ASM692ACSA ASM692AEPA ASM692AESA ASM802L ASM802LCPA ASM802LCSA ASM802LEPA ASM802LESA ASM802M ASM802MCPA ASM802MCSA ASM802MEPA ASM802MESA ASM805L ASM805LCPA ASM805LCSA ASM805LEPA ASM805LESA 4.75 4.75 4.75 4.75 4.25 4.50 4.25 4.50 4.25 4.50 4.25 4.50 4.75 4.75 4.75 4.75 4.25 4.50 4.25 4.50 4.25 4.50 4.25 4.50 4.75 4.75 4.75 4.75 Reset Threshold Temperature (°C)
ASM690A/692A ASM802L/802M ASM805L
Pins-Package 8-Plastic 8-SO 8-Plastic 8-SO 8-Plastic 8-SO 8-Plastic 8-SO 8-Plastic 8-SO 8-Plastic 8-SO 8-Plastic 8-SO 8-Plastic 8-SO 8-Plastic 8-SO 8-Plastic 8-SO
Package Marking
ASM690ACPA ASM690ACSA ASM690AEPA ASM690AESA ASM692ACPA ASM692ACSA ASM692AEPA ASM692AESA ASM802LCPA ASM802LCSA ASM802LEPA ASM802LESA ASM802MCPA ASM802MCSA ASM802MEPA ASM802MESA ASM805LCPA ASM805LCSA ASM805LEPA ASM805LESA
Power Supply Supervisor With Battery Backup Switch
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April 2008 Ordering Information Lead Free Devices
Part Number
ASM690A ASM690ACPAF ASM690ACSAF ASM690AEPAF ASM690AESAF ASM692A ASM692ACPAF ASM692ACSAF ASM692AEPAF ASM692AESAF ASM802L ASM802LCPAF ASM802LCSAF ASM802LEPAF ASM802LESAF ASM802M ASM802MCPAF ASM802MCSAF ASM802MEPAF ASM802MESAF ASM805L ASM805LCPAF ASM805LCSAF ASM805LEPAF ASM805LESAF 4.75 4.75 4.75 4.75 4.25 4.50 4.25 4.50 4.25 4.50 4.25 4.50 4.75 4.75 4.75 4.75 4.25 4.50 4.25 4.50 4.25 4.50 4.25 4.50 4.75 4.75 4.75 4.75 Reset Threshold(V) Temperature(°C)
ASM690A/692A ASM802L/802M ASM805L
Pins-Package 8-Plastic 8-SO 8-Plastic 8-SO 8-Plastic 8-SO 8-Plastic 8-SO 8-Plastic 8-SO 8-Plastic 8-SO 8-Plastic 8-SO 8-Plastic 8-SO 8-Plastic 8-SO 8-Plastic 8-SO
Package Marking
ASM690ACPAF ASM690ACSAF ASM690AEPAF ASM690AESAF ASM692ACPAF ASM692ACSAF ASM692AEPAF ASM692AESAF ASM802LCPAF ASM802LCSAF ASM802LEPAF ASM802LESAF ASM802MCPAF ASM802MCSAF ASM802MEPAF ASM802MESAF ASM805LCPAF ASM805LCSAF ASM805LEPAF ASM805LESAF
Notes: parts packed Tape Reel, "-T" part number. PulseCore Semiconductor's lead free parts RoHS compliant.
Power Supply Supervisor With Battery Backup Switch
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ASM690A/692A ASM802L/802M ASM805L
PulseCore Semiconductor Corporation 1715 Bascom Suite Campbell, 95008 Tel: 408-879-9077 Fax: 408-879-9018 www.pulsecoresemi.com
Copyright PulseCore Semiconductor Rights Reserved Part Number: ASM690A 692A ASM802L 802M ASM805L Document Version:
Copyright 2006 PulseCore Semiconductor Corporation. rights reserved. logo name trademarks registered trademarks PulseCore Semiconductor. other brand product names trademarks their respective companies. PulseCore reserves right make changes this document products time without notice. PulseCore assumes responsibility errors that appear this document. data contained herein represents PulseCore's best data and/or estimates time issuance. PulseCore reserves right change correct this data time, without notice. product described herein under development, significant changes these specifications possible. information this product data sheet intended general descriptive information potential customers users, intended operate provide, guarantee warrantee user customer. PulseCore does assume responsibility liability arising application product described herein, disclaims express implied warranties related sale and/or PulseCore products including liability warranties related fitness particular purpose, merchantability, infringement intellectual property rights, except express agreed PulseCore's Terms Conditions Sale (which available from PulseCore). sales PulseCore products made exclusively according PulseCore's Terms Conditions Sale. purchase products from PulseCore does convey license under patent rights, copyrights; mask works rights, trademarks, other intellectual property rights PulseCore third parties. PulseCore does authorize products critical components life-supporting systems where malfunction failure reasonably expected result significant injury user, inclusion PulseCore products such life-supporting systems implies that manufacturer assumes risk such agrees indemnify PulseCore against claims arising from such use.
Power Supply Supervisor With Battery Backup Switch
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Power Supply Supervisor With Battery Backup Switch ASM690A ASM692

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