Datasheet
PCF2127AT All information provided in this document is subject to legal disclaimers. © NXP B.V. 2013. All rights reserved.
Product data sheet Rev. 6 — 11 July 2013 15 of 86
NXP Semiconductors
PCF2127AT
Integrated RTC, TCXO and quartz crystal
8.4 Register Aging_offset
8.4.1 Crystal aging correction
The PCF2127AT has an offset register Aging_offset to correct the crystal aging effects
3
.
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.
At 25 C, the aging offset bits allow a frequency correction of typically 1 ppm per AO[3:0]
value, from 7 ppm to +8 ppm.
[1] Default value.
Table 12. Aging_offset - crystal aging offset register (address 19h) bit description
Bit Symbol Value Description
7 to 4 - - unused
3 to 0 AO[3:0] see Table 13
aging offset value
3. For further information, refer to the application note Ref. 3 “AN10857”.
Table 13. Frequency correction at 25C, typical
AO[3:0] ppm
Decimal Binary
00000+8
10001+7
20010+6
30011+5
40100+4
50101+3
60110+2
70111+1
81000
[1]
0
910011
10 1010 2
11 1011 3
12 1100 4
13 1101 5
14 1110 6
15 1111 7