PCF85263ATSLASHA datasheet(40/92 Pages) NXP

40 / 92 page

NXP Semiconductors

PCF85263A

Tiny Real-Time Clock/calendar with alarm function, battery switch-over, time stamp input, and I2C-bus

The PCF85263A is designed to operate with quartz with CL values of 6.0 pF, 7.0 pF and

12.5 pF.

12.5 pF are generally the cheapest and most widely available, but also require the most

power to drive. The circuit also operates with 9.0 pF quartz, however the offset calibration

would be needed to compensate. If a 9.0 pF quartz is used, then it is recommended to

set CL to 7.0 pF.

7.11 Battery switch register

This register configures the battery switch-over mode.

Associated with the battery switch-over is the battery switch flag (BSF) in the Flags

The flag can only be read when operating from VDD power, however an interrupt pulse or

static LOW signal can be generated whenever switching to battery. An interrupt pulse can

also be generated when switching back to VDD power. Examples are given in Figure 25

and Figure 26.

When switched to battery, the VDD power domain is disabled. This means that I2C pins

are ignored, CLK output is disabled and Hi-Z, TS pin output mode is disabled and Hi-Z,

TS digital input is ignored and may be left floating. TS pin mechanical switch detector

is active. INTA output is still active for interrupt output and battery switch indication, but

disabled for clock output.

IO pin (mode)

VDD operation

VBAT operation

SCL

active input

disabled; may be left floating

SDA

active input/output

disabled; may be left floating

CLK

active output

disabled; Hi-Z

TS (output mode)

active output

disabled; Hi-Z

TS (digital input)

active input

disabled; may be left floating

TS (mechanical switch input)

active input

INTA

active output

active interrupt output

Table 35. IO pin behavior in battery mode

Bit

Symbol

BSOFF

BSRR

BSM[1:0]

BSTH

Section

Section 7.11.1

Section 7.11.2

Section 7.11.3

Section 7.11.4

Table 36. Battery_switch - battery switch control (address 26h) bit description

7.11.1 BSOFF: battery switch on/off control

Bit

Symbol

Value

Description

battery switch on/off

0 [1]

enable battery switch feature

BSOFF

disable battery switch feature

Table 37. BSOFF bit - battery switch control (address 26h) bit description

PCF85263A

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Product data sheet

Rev. 5 — 1 February 2021

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