LTC692/LTC693
Microprocessor
Supervisory Circuits
FEATURES
DESCRIPTION
The LTC®692/LTC693 provide complete power supply
monitoringandbatterycontrolfunctionsformicroproces-
sor reset, battery backup, CMOS RAM write protection,
power failure warning and watchdog timing. A precise
internal voltage reference and comparator circuit monitor
thepowersupplyline. Whenanout-of-tolerancecondition
occurs,theresetoutputsareforcedtoactivestatesandthe
chipenableoutputunconditionallywrite-protectsexternal
memory. In addition, the RESET output is guaranteed to
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Guaranteed Reset Assertion at V = 1V
CC
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1.5mA Maximum Supply Current
Fast (35ns Maximum) Onboard Gating of RAM Chip
Enable Signals
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4.40V Precision Voltage Monitor
Power OK/Reset Time Delay: 200ms or Adjustable
Minimum External Component Count
1μA Maximum Standby Current
Voltage Monitor for Power-Fail or Low Battery
Warning
remain logic low even with V as low as 1V.
CC
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Thermal Limiting
The LTC692/LTC693 power the active CMOS RAMs with a
charge-pumped NMOS power switch to achieve low drop-
out and low supply current. When primary power is lost,
auxiliarypower, connectedtothebatteryinputpin, powers
the RAMs in standby through an efficient PMOS switch.
Performance Specified Over Temperature
Superior Upgrade for MAX690 Family
SO8 and SO16 Packaging
APPLICATIONS
For an early warning of impending power failure, the
LTC692/LTC693 provide an internal comparator with a
user-defined threshold. An internal watchdog timer is
also available, which forces the reset pins to active states
when the watchdog input is not toggled prior to a preset
timeout period.
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Critical μP Power Monitoring
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Intelligent Instruments
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Battery-Powered Computers and Controllers
Automotive Systems
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L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners..
TYPICAL APPLICATION
RESET Output Voltage vs
Supply Voltage
5
T
= 25°C
A
EXTERNAL PULL-UP = 10μA
= 0V
LT1086-5
V
≥ 7.5V
IN
5V
V
BATT
4
3
POWER TO
μP
V
V
V
CC
V
IN
OUT
OUT
+
+
CMOS RAM POWER
0.1μF
3V
0.1μF
LTC692
LTC693
100μF
10μF
ADJ
μP
SYSTEM
V
BATT
μP RESET
μP NMI
RESET
PFO
2
1
0
51k
10k
I/O LINE
PFI
WDI
GND
692_3 • TA01
0.1μF
100Ω
MICROPROCESSOR RESET, BATTERY BACKUP, POWER FAILURE
WARNING AND WATCHDOG TIMING ARE ALL IN A SINGLE CHIP
FOR MICROPROCESSOR SYSTEMS
0
1
2
3
4
5
SUPPLY VOLTAGE (V)
692_3 • TA02
0692fb
1