PCF2127 View Datasheet(PDF) - NXP Semiconductors.
Part Name
Description
MFG CO.
'PCF2127' PDF : 101 Pages View PDF
NXP Semiconductors
PCF2127
Accurate RTC with integrated quartz crystal for industrial applications
Table 15. CLKOUT frequency selection
COF[2:0]
CLKOUT frequency (Hz)
000
[2][3] 32768
001
16 384
010
8 192
011
4 096
100
2 048
101
1 024
110
1
111
CLKOUT = high-Z
Typical duty cycle[1]
60 : 40 to 40 : 60
50 : 50
50 : 50
50 : 50
50 : 50
50 : 50
50 : 50
-
[1] Duty cycle definition: % HIGH-level time : % LOW-level time.
[2] Default value.
[3] The specified accuracy of the RTC can be only achieved with CLKOUT frequencies not equal to
32.768 kHz or if CLKOUT is disabled.
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.
8.4 Register Aging_offset
Table 16. Aging_offset - crystal aging offset register (address 19h) bit allocation
Bit positions labeled as - are not implemented and return 0 when read.
Bit
7
6
5
4
3
2
1
0
Symbol
-
-
-
-
AO[3:0]
Reset
-
-
-
-
1
0
0
0
value
Table 17. Aging_offset - crystal aging offset register (address 19h) bit description
Bit positions labeled as - are not implemented and return 0 when read.
Bit
Symbol
Value
Description
7 to 4
-
-
unused
3 to 0
AO[3:0]
see Table 18
aging offset value
8.4.1 Crystal aging correction
The PCF2127 has an offset register Aging_offset to correct the crystal aging effects2.
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.
2. For further information, refer to the application note Ref. 3 “AN11266”.
PCF2127
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 8 — 19 December 2014
© NXP Semiconductors N.V. 2014. All rights reserved.
14 of 100
Share Link: 
