DESCRIPTION
The LTC690 family provides complete power supply
monitoring and battery control functions for microproces-
sor reset, battery back-up, 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 LTC690 family powers 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
LTC690 family provides 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.
FEATURES
UL Recognized File # E145770
Guaranteed Reset Assertion at VCC = 1V
1.5mA Maximum Supply Current
Fast (35ns Max) Onboard Gating of RAM Chip
Enable Signals
SO-8 and S16 Packaging
4.65V Precision Voltage Monitor
Power OK/Reset Time Delay: 50ms, 200ms
or Adjustable
Minimum External Component Count
1µA Maximum Standby Current
Voltage Monitor for Power-Fail
or Low-Battery Warning
Thermal Limiting
Performance Specified Over Temperature
Superior Upgrade for MAX690 Family
APPLICATIONS
Critical Power Monitoring
Intelligent Instruments
Battery-Powered Computers and Controllers
Automotive Systems
TYPICAL APPLICATION (1)
RESET Output Voltage vs Supply Voltage (2)
N PACKAGE (3)
SW PACKAGE (4)
J8 / N8 PACKAGE (5)
S8 PACKAGE (6)
P/N Package
LTC691CN DIP-16
LTC691IN DIP-16
LTC695CN DIP-16
LTC695IN DIP-16
LTC691CSW SOP-16
LTC691ISW SOP-16
LTC695CSW SOIC16
LTC695ISW SOP-16
LTC690CN8 DIP-8
LTC690IN8 DIP-8
LTC690MJ8 DIP-8
LTC694CN8 DIP-8
LTC694IN8 DIP-8
LTC690CS8 SOP-8
LTC690IS8 SOP-8
LTC694CS8 SOP-8
LTC694IS8 SOP-8