M41ST85W_11 Datasheet, PDF (1/43 Pages) STMicroelectronics – 3.0/3.3 V I2C combination serial RTC, NVRAM supervisor and microprocessor supervisor

M41ST85W
3.0/3.3 V 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)
■ 400 kHz I²C serial interface
■ 3.0/3.3 V operating voltage
– V_CC = 2.7 to 3.6 V
■ Ultralow battery supply current of 500 nA (max)
■ RoHS compliant
– Lead-free second level interconnect
Serial RTC features
■ 400 kHz I²C
■ 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
SNAPHAT battery & crystal
28
1
SOH28
Embedded crystal
SOX28
■ Power-on reset/low voltage detect
– Open drain reset output
– Reset voltage, V_PFD = 2.60 V (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 = 2.60 V (nom)
– Switchover, V_SO = 2.50 V (nom)
■ 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^® IC (SOH28) SNAPHAT
battery/crystal top to be ordered separately
– 28-lead embedded crystal SOIC (SOX28)
October 2011
Doc ID 7531 Rev 11
1/43
www.st.com
1