M41ST85W_07 Datasheet, PDF (1/41 Pages) STMicroelectronics – 3.0/3.3V I2C combination serial RTC, NVRAM supervisor and microprocessor supervisor

M41ST85W
3.0/3.3V I²C combination serial RTC, NVRAM
supervisor and microprocessor supervisor
Features
■ Automatic battery switchover and WRITE
protect for:
– Internal serial RTC and
– External low power SRAM (LPSRAM)
■ 400kHz I²C serial interface
■ 3.0/3.3V operating voltage
– V_CC = 2.7 to 3.6V
■ Ultra-low battery supply current of 500nA (max)
■ RoHS compliant
– Lead-free second level interconnect
Serial RTC features
■ 400kHz I²C
■ 44 bytes of general purpose NVRAM
■ Counters for:
– Seconds, minutes, hours, day, date, month,
and year
– Century
– 10ths/100ths 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 5.5V oscillator operating voltage
Microprocessor supervisor features
■ Programmable watchdog
– 62.5ms to 128s time-out period
■ Early power-fail warning circuit (PFI/PFO) with
1.25V precision reference
SNAPHAT (SH) battery & crystal
28
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SOH28 (MH)
Embedded crystal
SOX28 (MX)
■ Power-on reset/low voltage detect
– Open drain reset output
– Reset voltage, V_PFD = 2.60V (nom)
– 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_PFD = 2.60V (nom)
– Switchover , V_SO = 2.50V (nom)
■ Battery monitor (battery low flag)
Other features
■ Programmable squarewave generator (1Hz to
32KHz)
■ –40°C to +85°C Operation
■ Package options:
– 28-lead SNAPHAT^® IC (SOH28) SNAPHAT
battery/crystal top to be ordered separately
– 28-lead embedded crystal SOIC (SOX28)
October 2007
Rev 9
1/41
www.st.com
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