ST M41ST85W Manual

Features
■
Automatic battery switchover and WRITE
protect for:
– Internal serial RTC and
– External low power SRAM (LPSRAM)
2
■
400 kHz I C serial interface
■ 3.0/3.3 V operating voltage
– V = 2.7 to 3.6 V
CC
■ Ultralow battery supp
■
RoHS compliant
– Lead-free second level interconnect
Serial RTC features
2
■ 400 kHz I C
■
44 bytes of general purpose NVRAM
■
Counters for:
– Seconds, minutes, hours, day, date, month,
and year
– Century
– Tenths/hundredths of seconds
– Clock calibration register allows
compensation for crystal variations over
temperature
■
Programmable alarm with repeat modes
– Functions in battery back-up mode
■
Power-down timestamp (HT bit)
■
2.5 to 5.5 V oscillator operating voltage
Microprocessor supervisor features
■
Programmable watchdog
– 62.5 ms to 128 s time-out period
■
Early power-fail warning circuit (PFI/PFO) with
1.25 V precision reference
October 2011
3.0/3.3 V I
supervisor and microprocessor supervisor
y current of 500 nA max
l (
Doc ID 7531 Rev 11
2
C combination serial RTC, NVRAM
SNAPHAT battery & crystal
)
■
Power-on reset/low voltage detect
– Open drain reset output
– Reset voltage, V
– Two reset input pins
– Watchdog can be steered to reset output
NVRAM supervisor features
■
Non-volatizes external LPSRAM
– Automatically switches to back-up battery
and deselects (write-protects) external
LPSRAM via chip-enable gate
– Power-fail deselect (write protect) voltage,
V = 2.60 V (nom)
PFD
– Switchover, V
■
Battery monitor (battery low flag)
Other features
■
Programmable squarewave generator (1 Hz to
32 KHz)
■
–40°C to +85°C operation
■
Package options:
– 28-lead SNAPHAT
battery/crystal top to be ordered separately
– 28-lead embedded crystal SOIC (SOX28)
M41ST85W
28
1
SOH28
Embedded crystal
SOX28
= 2.60 V (nom)
PFD
= 2.50 V (nom)
SO
®
IC (SOH28) SNAPHAT
1/43
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