PCF2127AT datasheet(23/100 Pages) PHILIPS

Part #	PCF2127AT

Description	Accurate RTC with integrated quartz crystal for industrial applications

PDF	100 Pages

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Manufacturer	PHILIPS [NXP Semiconductors]

Direct Link	http://www.nxp.com

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23 / 100 page

PCF2127

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Product data sheet

Rev. 8 — 19 December 2014

23 of 100

NXP Semiconductors

PCF2127

Accurate RTC with integrated quartz crystal for industrial applications

8.6.3 Extra power fail detection function

The PCF2127 has an extra power fail detection circuit which compares the voltage at the

power fail input pin PFI to an internal reference voltage equal to 1.25 V.

If VPFI < 1.25 V, the power fail output PFO is driven LOW. PFO is an open-drain, active

LOW output which requires an external pull-up resistor in any application.

The extra power fail detection function is typically used as a low voltage detection for the

main power supply VDD (see Figure 10).

Fig 9.

Battery low detection behavior with bit BLIE set logic 1 (enabled)

Fig 10. Typical application of the extra power fail detection function

PCF2127AT Datasheet(PDF) 23 Page - NXP Semiconductors