The MAX6916 provides all the features of a real-time
clock (RTC) plus a microprocessor supervisory circuit,
NV RAM controller, and backup-battery monitor function.
In addition, 96 x 8 bits of static RAM are available
for scratchpad storage. The MAX6916 communicates
with a microprocessor through an SPI™-bus-compatible
serial interface.
The real-time clock/calendar provides seconds, minutes,
hours, day, date, month, and year information.
The end of the month date is automatically adjusted for
months with fewer than 31 days, including corrections
for leap years through 2099. The clock operates in
either 24hr or 12hr format with an AM/PM indicator. A
time/date-programmable alarm function is provided
with an open-drain, active-low alarm output.
The microprocessor supervisory circuit features an
open-drain, active-low reset available in three different
reset thresholds. A manual reset input and a watchdog
function are included as well.
The NV RAM controller provides power for external SRAM
from a backup battery plus chip-enable gating. The backup
battery also provides data retention of the on-board 96
x 8 bits of RAM. An open-drain, active-low, battery-on signal
alerts the system when operating from a battery.
The battery-test circuitry periodically tests the backup
battery for a low-battery condition. An optional external
resistor network selects different battery thresholds. A
freshness seal prevents battery drain until the first VCC
power-up.
The MAX6916 has a crystal-fail-detect circuit and a
data-valid bit. The MAX6916 is available in a 20-pin
QSOP package and is guaranteed to operate over the
extended temperature range from -40°C to +85°C.
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