M41ST85W
3.0/3.3 V I2C combination serial RTC, NVRAM
supervisor and microprocessor supervisor
Features
SNAPHAT battery & crystal
■
Automatic battery switchover and WRITE
protect for:
– Internal serial RTC and
– External low power SRAM (LPSRAM)
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400 kHz I2C serial interface
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3.0/3.3 V operating voltage
– VCC = 2.7 to 3.6 V
■
Ultralow battery supply current of 500 nA (max)
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RoHS compliant
– Lead-free second level interconnect
28
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SOH28
Embedded crystal
Serial RTC features
SOX28
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400 kHz I2C
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44 bytes of general purpose NVRAM
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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
■
Power-on reset/low voltage detect
– Open drain reset output
– Reset voltage, VPFD = 2.60 V (nom)
– Two reset input pins
– Watchdog can be steered to reset output
NVRAM supervisor features
Power-down timestamp (HT bit)
■
Battery monitor (battery low flag)
Programmable alarm with repeat modes
– Functions in battery back-up mode
■
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,
VPFD = 2.60 V (nom)
– Switchover, VSO = 2.50 V (nom)
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■
■
2.5 to 5.5 V oscillator operating voltage
Microprocessor supervisor features
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Other 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
Programmable squarewave generator (1 Hz to
32 KHz)
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–40°C to +85°C operation
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■
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Package options:
– 28-lead SNAPHAT® IC (SOH28) SNAPHAT
battery/crystal top to be ordered separately
– 28-lead embedded crystal SOIC (SOX28)
Doc ID 7531 Rev 11
1/43
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