Microprocessor
Supervisory Circuits
a
ADM8696/ADM8697
FUNCTIO NAL BLO CK D IAGRAMS
FEATURES
Upgrade for ADM696/ ADM697, MAX696/ MAX697
Specified Over Tem perature
BATT ON
V
Adjustable Low Line Voltage Monitor
Pow er OK/ Reset Tim e Delay
BATT
V
OUT
Reset Assertion Dow n to 1 V VCC
Watchdog Tim er—100 m s, 1.6 s, or Adjustable
Low Sw itch On Resistance
0.7 ⍀ Norm al, 7 ⍀ in Backup
400 nA Standby Current
Autom atic Battery Backup Sw itching (ADM8696)
Fast On-Board Gating of Chip Enable Signals (ADM8697)
Voltage Monitor for Pow er Fail or Low Battery Warning
Also Available in TSSOP Package
V
CC
LL
IN
LOW LINE
RESET
RESET GENERATOR
RESET
OSC IN
TIMEBASE FOR RESET
AND WATCHDOG
OSC SEL
WATCHDOG
OUTPUT (WDO)
WATCHDOG
TIMER
APPLICATIONS
Microprocessor System s
Com puters
Controllers
Intelligent Instrum ents
Autom otive System s
Critical P Pow er Monitoring
WATCHDOG
INPUT (WDI)
WATCHDOG
TRANSITION DETECTOR
ADM8696
POWER FAIL
INPUT (PFI)
POWER FAIL
OUTPUT (PFO)
1.3V
GENERAL D ESCRIP TIO N
CE
LL
IN
CE
T he ADM8696/ADM8697 supervisory circuits offer 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 warning.
OUT
IN
LOW LINE
RESET
RESET GENERATOR
RESET
T he ADM8696/ADM8697 are available in 16-pin DIP and small
outline packages (including T SSOP) and provide the following
functions:
OSC IN
TIMEBASE FOR RESET
AND WATCHDOG
OSC SEL
WATCHDOG
OUTPUT (WDO)
WATCHDOG
TIMER
1. Power-On Reset output during power-up, power-down and
brownout conditions. T he RESET voltage threshold is
adjustable using an external voltage divider. T he RESET out-
put remains operational with VCC as low as 1 V.
WATCHDOG
INPUT (WDI)
WATCHDOG
TRANSITION DETECTOR
ADM8697
POWER FAIL
INPUT (PFI)
POWER FAIL
OUTPUT (PFO)
2. A Reset pulse if the optional watchdog timer has not been
toggled within specified time.
1.3V
3. Separate watchdog timeout and low line status outputs.
4. Adjustable reset and watchdog timeout periods.
T he ADM8696/ADM8697 is fabricated using an advanced
epitaxial CMOS process combining low power consumption
(0.7 mW), extremely fast Chip Enable gating (2 ns) and high re-
liability. 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.
5. A 1.3 V threshold detector for power fail warning, low battery
detection or to monitor a power supply other than VCC
.
6. Battery backup switching for CMOS RAM, CMOS micro-
processor or other low power logic (ADM8696).
7. Write protection of CMOS RAM or EEPROM (ADM8697).
REV. 0
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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
otherwise under any patent or patent rights of Analog Devices.
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© Analog Devices, Inc., 1997