Microprocessor
Supervisory Circuits
a
ADM690–ADM695
FEATURES
FUNCTIO NAL BLO CK D IAGRAMS
Superior Upgrade for MAX690–MAX695
Specified Over Tem perature
VBATT
Low Pow er Consum ption (5 m W)
Precision Voltage Monitor
Reset Assertion Dow n to 1 V VCC
Low Sw itch On-Resistance 1.5 ⍀ Norm al,
20 ⍀ in Backup
VOUT
VCC
RESET
4.65V1
GENERATOR2
RESET
High Current Drive (100 m A)
Watchdog Tim er—100 m s, 1.6 s, or Adjustable
600 nA Standby Current
Autom atic Battery Backup Pow er Sw itching
Extrem ely Fast Gating of Chip Enable Signals (5 ns)
Voltage Monitor for Pow er Fail
WATCHDOG
TRANSITION DETECTOR
(1.6s)
WATCHDOG
INPUT (WDI)
ADM690
ADM692
ADM694
POWER FAIL
INPUT (PFI)
POWER FAIL
OUTPUT (PFO)
APPLICATIONS
1.3V
Microprocessor System s
Com puters
1VOLTAGE DETECTOR = 4.65V (ADM690, ADM694)
4.40V (ADM692)
Controllers
Intelligent Instrum ents
Autom otive System s
2RESET PULSE WIDTH = 50ms (ADM690, ADM692)
200ms (ADM694)
BATT ON
VBATT
GENERAL D ESCRIP TIO N
T he ADM690–ADM695 family of supervisory circuits offers
complete single chip solutions for power supply monitoring and
battery control functions in microprocessor systems. T hese
functions include µP reset, backup battery switchover, watchdog
timer, CMOS RAM write protection, and power failure warn-
ing. T he complete family provides a variety of configurations to
satisfy most microprocessor system requirements.
VOUT
ADM691
ADM693
ADM695
VCC
CEIN
CEOUT
LOW LINE
4.65V1
RESET
RESET
T he ADM690, ADM692 and ADM694 are available in 8-pin
DIP packages and provide:
RESET &
RESET
OSC IN
WATCHDOG
GENERATOR
OSC SEL
TIMEBASE
1. Power-on reset output during power-up, power-down and
brownout conditions. T he RESET output remains opera-
tional with VCC as low as 1 V.
WATCHDOG
TIMER
WATCHDOG
WATCHDOG
INPUT (WDI)
WATCHDOG
OUTPUT (WDO)
TRANSITION DETECTOR
2. Battery backup switching for CMOS RAM, CMOS
microprocessor or other low power logic.
POWER FAIL
INPUT (PFI)
POWER FAIL
OUTPUT (PFO)
3. A reset pulse if the optional watchdog timer has not been
toggled within a specified time.
1.3V
1VOLTAGE DETECTOR = 4.65V (ADM691, ADM695)
4.40V (ADM693)
4. A 1.3 V threshold detector for power fail warning, low battery
detection, or to monitor a power supply other than +5 V.
T he ADM690–ADM695 family is fabricated using an advanced
epitaxial CMOS process combining low power consumption
(5 mW), extremely fast Chip Enable gating (5 ns) and high reli-
ability. RESET assertion is guaranteed with VCC as low as 1 V.
In addition, the power switching circuitry is designed for mini-
mal voltage drop thereby permitting increased output current
drive of up to 100 mA without the need for an external pass
transistor.
T he ADM691, ADM693 and ADM695 are available in 16-pin
DIP and small outline packages and provide three additional
functions.
1. Write protection of CMOS RAM or EEPROM.
2. Adjustable reset and watchdog timeout periods.
3. Separate watchdog timeout, backup battery switchover, and
low VCC status outputs.
REV. A
© Analog Devices, Inc., 1996
Inform ation furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assum ed by Analog Devices for its
use, nor for any infringem ents of patents or other rights of third parties
which m ay result from its use. No license is granted by im plication or
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