DS1251 Datasheet, PDF (7/22 Pages) Dallas Semiconductor – 4096k NV SRAM with Phantom Clock

DS1251/DS1251P
BATTERY LONGEVITY
The DS1251 has a lithium power source that is designed to provide energy for clock activity, and clock
and RAM data retention when the V_CC supply is not present. The capability of this internal power supply
is sufficient to power the DS1251 continuously for the life of the equipment in which it is installed. For
specification purposes, the life expectancy is 10 years at +25°C with the internal clock oscillator running
in the absence of V_CC power. Each DS1251 is shipped from Dallas Semiconductor with its lithium energy
source disconnected, guaranteeing full energy capacity. When VCC is first applied at a level greater than
VPF, the lithium energy source is enabled for battery-backup operation. Actual life expectancy of the
DS1251 will be much longer than 10 years since no lithium battery energy is consumed when VCC is
present.
CLOCK ACCURACY (DIP MODULE)
The DS1251 is guaranteed to keep time accuracy to within ±1 minute per month at +25°C. The clock is
calibrated at the factory by Dallas Semiconductor using special calibration nonvolatile tuning elements.
The DS1251 does not require additional calibration and temperature deviations will have a negligible
effect in most applications. For this reason, methods of field clock calibration are not available and not
necessary.
CLOCK ACCURACY (POWERCAP MODULE)
The DS1251P and DS9034PCX are each individually tested for accuracy. Once mounted together, the
module is guaranteed to keep time accuracy to within ±1.53 minutes per month (35ppm) at +25°C.
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