DS1248 Datasheet, PDF (7/21 Pages) Dallas Semiconductor – 1024k NV SRAM with Phantom Clock

DS1248/DS1248P
BATTERY LONGEVITY
The DS1248 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 DS1248 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 DS1248 is shipped from Dallas Semiconductor with its lithium energy
source disconnected, guaranteeing full energy capacity. When V_CC is first applied at a level greater than
V_PF, the lithium energy source is enabled for battery-backup operation. Actual life expectancy of the
DS1248 will be much longer than 10 years since no lithium battery energy is consumed when V_CC is
present.
CLOCK ACCURACY (DIP MODULE)
The DS1248 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
and does not require additional calibration. For this reason, methods of field clock calibration are not
available and not necessary.
CLOCK ACCURACY (POWERCAP MODULE)
The DS1248P and DS9034PCX are each individually tested for accuracy. Once mounted together, the
module will typically keep time accuracy to within ±1.53 minutes per month (35ppm) at +25°C.
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