PCF8564A datasheet(16/86 Pages) NXP

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NXP Semiconductors

PCA2131

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

COF[2:0]

CLKOUT frequency (Hz)

Typical duty cycle [1]

000

[2] 32 768

60 : 40 to 40 : 60

001

16 384

50 : 50

010

8 192

50 : 50

011

4 096

50 : 50

100

2 048

50 : 50

101

1 024

50 : 50

110

50 : 50

111

CLKOUT = high-Z

Table 18. CLKOUT frequency selection

[1]

Duty cycle definition: % HIGH-level time: % LOW-level time.

[2]

Default value.

The duty cycle of the selected clock is not controlled, however, due to the nature of the

clock generation all but the 32.768 kHz frequencies are 50 : 50.

7.4 Register Aging_offset

Bits labeled as T are unused and return 0 when read.

Bit

Symbol

AO[3:0]

Reset

value

Table 19. Aging_offset - crystal aging offset register (address 30h) bit allocation

Bits labeled as T are unused and return 0 when read.

Bit

Symbol

Value

Description

7 to 4

0000

unused

3 to 0

AO[3:0]

see Table 21

aging offset value

Table 20. Aging_offset - crystal aging offset register (address 30h) bit description

7.4.1 Crystal aging correction

The PCA2131 has an offset register Aging_offset to correct the crystal aging effects 1 .

The accuracy of the frequency of a quartz crystal depends on its aging. The aging offset

adds an adjustment, positive or negative, in the temperature compensation circuit which

allows correcting the aging effect.

The aging offset bits allow a frequency correction of typically 2 ppm per AO[3:0] value,

from -14 ppm to +16 ppm.

For further information, refer to the application note [1].

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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