The MAX696/MAX697 supervisory circuits reduce the
complexity and number of components required for
power-supply monitoring and battery-control functions
in microprocessor (µP) systems. These include µP reset
and backup-battery switchover, watchdog timer, CMOS
RAM write protection, and power-failure warning. The
MAX696/MAX697 significantly improve system reliability
and accuracy compared to that obtained with separate
ICs or discrete components.
The MAX696 and MAX697 are supplied in 16-pin packages
and perform six functions:
1) A reset output during power-up, power-down, and
brownout conditions. The threshold for this "lowline"
reset is adjustable by an external voltage-divider.
2) A reset pulse if the optional watchdog timer has not
been toggled within a specified time.
3) Individual outputs for low-line and watchdog fault
conditions.
4) The reset time may be left at its default value of
50ms, or may be varied with an external capacitor
or clock pulses.
5) A separate 1.3V threshold detector for power-fail
warning, low-battery detection, or to monitor a
power supply other than VCC.
The MAX696 also has battery-backup switching for
CMOS RAM, CMOS microprocessor, or other low-power
logic.
The MAX697 lacks battery-backup switching, but has
write-protection pins (CE-bar IN and CE-bar OUT) for CMOS
RAM or EPROM. In addition, it consumes less than 250
microamperes.
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