LTC693_15 Datasheet, PDF (1/20 Pages) Linear Technology – Microprocessor Supervisory Circuits

LTC692/LTC693
Microprocessor
Supervisory Circuits
FEATURES
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 Specified 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 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/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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TYPICAL APPLICATION
V_IN ≥ 7.5V
+
10μF
LT1086-5
V_IN
V_OUT
ADJ
5V
+
100μF
51k
0.1μF
3V
V_CC
V_OUT
LTC692
LTC693
V_BATT
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
T_A = 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
0692fb
1