PCF8564A datasheet(5/86 Pages) NXP

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NXP Semiconductors

PCA2131

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

Input or input/output pins must always be at a defined level (VSS or VDD) unless otherwise specified.

Symbol

Description

VBAT

battery supply voltage (backup)

connect to VSS if battery switch-over is not used

VDD

supply voltage

Exposed Pad

Tie to VSS (preferred)[1] or leave floating

Table 3. Pin description...continued

[1]

This protects against signal feedback to the oscillator if routed close to the part.

7 Functional description

The PCA2131 is a Real Time Clock (RTC) and calendar with an on-chip Temperature

Compensated Crystal (Xtal) Oscillator (TCXO) and a 32.768 kHz quartz crystal integrated

into the same package.

Address and data are transferred by a selectable 400 kHz Fast-mode I2C-bus or a 4-line

SPI-bus with separate data input and output (see Section 7.16). The maximum speed of

the SPI-bus is 6.5 Mbit/s.

The PCA2131 has a backup battery input pin and backup battery switch-over circuit

which monitors the main power supply. The backup battery switch-over circuit

automatically switches to the backup battery when a power failure condition is detected

(see Section 7.5.1). Accurate timekeeping is maintained even when the main power

supply is interrupted.

A battery low detection circuit monitors the status of the battery (see Section 7.5.2).

When the battery voltage drops below a certain threshold value, a flag is set to indicate

that the battery must be replaced soon. This ensures the integrity of the data during

periods of battery backup.

7.1 Register overview

The PCA2131 contains an auto-incrementing address register: the built-in address

(see Figure 3).

aaa-041564

address register

00h

auto-increment

wrap around

01h

02h

03h

...

34h

35h

36h

Figure 3. Handling address registers

• The first five registers (memory address 00h, 01h, 02h, 03h and 04h) are used as

control registers (see Section 7.2).

PCA2131

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

Product data sheet

Rev. 1.0 — 26 July 2021

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