PCF2127TSLASH2Y datasheet(18/100 Pages) PHILIPS

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PCF2127

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Product data sheet

Rev. 8 — 19 December 2014

18 of 100

NXP Semiconductors

PCF2127

Accurate RTC with integrated quartz crystal for industrial applications

Three power management functions are implemented:

Battery switch-over function. monitoring the main power supply VDD and switching to

VBAT in case a power fail condition is detected (see Section 8.6.1).

Battery low detection function. monitoring the status of the battery, VBAT (see

Section 8.6.2).

Extra power fail detection function. monitoring the voltage at the power fail input pin,

PFI (see Section 8.6.3).

The power management functions are controlled by the control bits PWRMNG[2:0] (see

Table 25) in register Control_3 (see Table 11):

[1]

Default value.

[2]

When the battery switch-over function is disabled, the PCF2127 works only with the power supply VDD.

VBAT must be put to ground and the battery low detection function is disabled.

Table 25.

Power management control bit description

PWRMNG[2:0]

Function

000

[1] battery switch-over function is enabled in standard mode;

battery low detection function is enabled;

extra power fail detection function is enabled

001

battery switch-over function is enabled in standard mode;

battery low detection function is disabled;

extra power fail detection function is enabled

010

battery switch-over function is enabled in standard mode;

battery low detection function is disabled;

extra power fail detection function is disabled

011

battery switch-over function is enabled in direct switching mode;

battery low detection function is enabled;

extra power fail detection function is enabled

100

battery switch-over function is enabled in direct switching mode;

battery low detection function is disabled;

extra power fail detection function is enabled

101

battery switch-over function is enabled in direct switching mode;

battery low detection function is disabled;

extra power fail detection function is disabled

110

[2] battery switch-over function is disabled - only one power supply

(VDD);

battery low detection function is disabled;

extra power fail detection function is enabled

111

[2] battery switch-over function is disabled - only one power supply

(VDD);

battery low detection function is disabled;

extra power fail detection function is disabled

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