LTC692 Datasheet, PDF (1/16 Pages) Linear Technology – Microprocessor Supervisory Circuits

FEATURES
s _{UL Recognized ®®}
s _{Guaranteed Reset Assertion at VCC = 1V}
s _{1.5mA Maximum Supply Current}
s _{Fast (35ns Max.) On-Board Gating of RAM Chip}
Enable Signals
s _{SO8 and SO16 Packaging}
s _{4.40V Precision Voltage Monitor}
s _{Power OK/Reset Time Delay:}
200ms or Adjustable
s _{Minimum External Component Count}
s _{1µA Maximum Standby Current}
s _{Voltage Monitor for Power Fail or}
Low Battery Warning
s _{Thermal Limiting}
s _{Performance Specified Over Temperature}
s _{Superior Upgrade for MAX690 Family}
APPLICATI S
s _{Critical µP Power Monitoring}
s _{Intelligent Instruments}
s _{Battery-Powered Computers and Controllers}
s _{Automotive Systems}
LTC692/LTC693
Microprocessor
Supervisory Circuits
DESCRIPTIO
The LTC692/LTC693 provide complete power supply moni-
toring and battery control functions for microprocessor
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 exter-
nal memory. In addition, the RESET output is guaranteed
to remain logic low even with V_CC 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 efficient PMOS switch.
For an early warning of impending power failure, the
LTC692/LTC963 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
time-out period.
TYPICAL APPLICATI
V_IN ≥ 7.5V
+
10µF
LT1086-5
V_IN
V_OUT
ADJ
5V
+
100µF
51k
10k
0.1µF
3V
V_CC
V_OUT
LTC692
LTC693
V_BATT
RESET
PFO
PFI _GND WDI
0.1µF
MICROPROCESSOR RESET, BATTERY BACKUP, POWER FAILURE
WARNING AND WATCHDOG TIMING ARE ALL IN A SINGLE CHIP
FOR MICROPROCESSOR SYSTEMS.
0.1µF
POWER TO µP
CMOS RAM POWER
µP
SYSTEM
µP RESET
µP NMI
I/O LINE
100Ω
LTC692/3 • TA01
RESET Output Voltage vs
Supply Voltage
5
T_A = 25°C
EXTERNAL PULL-UP = 10µA
4 VBATT = 0V
3
2
1
0
0
1
2
3
4
5
SUPPLY VOLTAGE (V)
LTC692/3 • TA02
1