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LTC692_09 Datasheet, PDF (1/20 Pages) Linear Technology – Microprocessor Supervisory Circuits | |||
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LTC692/LTC693
Microprocessor
Supervisory Circuits
FEATURES
n UL Recognized ®
n Guaranteed Reset Assertion at VCC = 1V
n 1.5mA Maximum Supply Current
n Fast (35ns Maximum) Onboard Gating of RAM Chip
Enable Signals
n 4.40V Precision Voltage Monitor
n Power OK/Reset Time Delay: 200ms or Adjustable
n Minimum External Component Count
n 1μA Maximum Standby Current
n Voltage Monitor for Power Fail or Low-Battery
Warning
n Thermal Limiting
n Performance Speciï¬ed Over Temperature
n Superior Upgrade for MAX690 Family
n SO8 and SO16 Packaging
APPLICATIONS
n Critical μP Power Monitoring
n Intelligent Instruments
n Battery-Powered Computers and Controllers
n Automotive Systems
DESCRIPTION
The LTC®692/LTC693 provide complete power supply
monitoring and battery control functions for microproces-
sor reset, battery backup, CMOS RAM write protection,
power failure warning and watchdog timing. A precise
internal voltage reference and comparator circuit monitor
the power supply line. When an out-of-tolerance condition
occurs, the reset outputs are forced to active states and the
chip enable output unconditionally write-protects external
memory. In addition, the RESET output is guaranteed to
remain logic low even with VCC as low as 1V.
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,
auxiliary power, connected to the battery input pin, powers
the RAMs in standby through an efï¬cient PMOS switch.
For an early warning of impending power failure, the
LTC692/LTC693 provide an internal comparator with a
user-deï¬ned 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
time-out period.
L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
VIN ⥠7.5V
+
10μF
LT1086-5
VIN
VOUT
ADJ
5V
+
100μF
51k
0.1μF
3V
VCC
VOUT
LTC692
LTC693
VBATT
RESET
PFO
PFI GND WDI
10k
MICROPROCESSOR RESET, BATTERY BACKUP, POWER FAILURE
WARNING AND WATCHDOG TIMING ARE ALL IN A SINGLE CHIP
FOR MICROPROCESSOR SYSTEMS
0.1μF
0.1μF
POWER TO μP
CMOS RAM POWER
μP
SYSTEM
μP RESET
μP NMI
I/O LINE
100Ω
692_3 ⢠TA01
RESET Output Voltage vs
Supply Voltage
5
TA = 25°C
EXTERNAL PULL-UP = 10μA
4 VBATT = 0V
3
2
1
0
0
1
2
3
4
5
SUPPLY VOLTAGE (V)
692_3 ⢠TA02
0692fa
1
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