Rainbow Electronics DS1643P - Manual (Page 5)

DS1643/DS1643P
5 of 14
level. The RST signal is an open drain output and requires a pull up. Except for the RST , all control, data,
and address signals must be powered down when V
CC
is powered down.
BATTERY LONGEVITY
The DS1643 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 DS1643 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 DS1643 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
Ds1643 will be much longer than 10 years since no lithium battery energy is consumed when V
CC
is
present.