PCF8564A datasheet(19/86 Pages) NXP

19 / 86 page

NXP Semiconductors

PCA2131

Nano-power highly accurate RTC with integrated quartz crystal for automotive applications

For further information about I2C-bus communication and battery backup operation, see

Section 7.16.3.

7.5.1.1 Standard mode

If VDD > VBAT OR VDD > Vth(sw)bat: Voper(int) is at VDD potential.

If VDD < VBAT AND VDD < Vth(sw)bat: Voper(int) is at VBAT potential.

001aaj311

internal operating voltage (Voper(int))

cleared via interface

backup battery operation

Vth(sw)bat

(= 2.5 V)

VDD (= 0 V)

VBAT

VDD

Voper(int)

INT

Vth(sw)bat is the battery switch threshold voltage. Typical value is 2.5 V. In standard mode, the

battery switch-over works only for VDD > 2.5 V.

VDD may be lower than VBAT (for example VDD = 3 V, VBAT = 4.1 V).

Figure 4. Battery switch-over behavior in standard mode with bit BIE set logic 1 (enabled)

7.5.1.2 Direct switching mode

If VDD > VBAT: Voper(int) is at VDD potential.

If VDD < VBAT: Voper(int) is at VBAT potential.

The direct switching mode is useful in systems where VDD is always higher than VBAT.

This mode is not recommended if the VDD and VBAT values are similar (for example,

VDD = 3.3 V, VBAT ≥ 3.0 V). In direct switching mode, the power consumption is reduced

compared to the standard mode because the monitoring of VDD and Vth(sw)bat is not

performed.

PCA2131

All information provided in this document is subject to legal disclaimers.

Product data sheet

Rev. 1.0 — 26 July 2021

19 / 86

PCF8564A Datasheet(PDF) 19 Page - NXP Semiconductors