DS1644P datasheet(6/13 Pages) DALLAS

Part #	DS1644P

Description	Nonvolatile Timekeeping RAM

PDF	13 Pages

Scroll/Zoom	100%

Manufacturer	DALLAS [Dallas Semiconductor]

Direct Link	https://www.maximintegrated.com/en.html

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6 / 13 page

DS1644/DS1644P

6 of 13

DATA RETENTION MODE

When VCC is within nominal limits (VCC > 4.5 volts) the DS1644 can be accessed as described above with

read or write cycles. However, when VCC is below the power-fail point VPF (point at which write

protection occurs) the internal clock registers and RAM are blocked from access. This is accomplished

internally by inhibiting access via the CE signal. At this time the power-fail output signal ( PFO ) will be

driven active low and will remain active until VCC returns to nominal levels. When VCC falls below the

level of the internal battery supply, power input is switched from the VCC pin to the internal battery and

clock activity, RAM, and clock data are maintained from the battery until VCC is returned to nominal

level.

DS1644P Datasheet(PDF) 6 Page - Dallas Semiconductor