DS1742 查看數據表（PDF） - Maxim Integrated

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DS1742

Y2KC Nonvolatile Timekeeping RAM

Maxim Integrated 

DS1742

BATTERY LONGEVITY

The DS1742 has a lithium power source that is designed to provide energy for clock activity,

and clock and RAM data retention when the VCC supply is not present. The capability of this

internal power supply is sufficient to power the DS1742 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 VCC power. Each DS1742 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 DS1742 will be

much longer than 10 years since no lithium battery energy is consumed when VCC is present.

BATTERY MONITOR

The DS1742 constantly monitors the battery voltage of the internal battery. The Battery Flag bit

(bit 7) of the day register is used to indicate the voltage level range of the battery. This bit is not

writable and should always be a 1 when read. If a 0 is ever present, an exhausted lithium

energy source is indicated and both the contents of the RTC and RAM are questionable.

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