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 20 of 86
NXP Semiconductors
PCF2127AT
Integrated RTC, TCXO and quartz crystal
8.6.1.1 Standard mode
If V
DD
> V
BAT
OR V
DD
>V
th(sw)bat
, the internal power supply is V
DD
.
If V
DD
< V
BAT
AND V
DD
<V
th(sw)bat
, the internal power supply is V
BAT
.
V
th(sw)bat
is the battery switch threshold voltage. Typical value is 2.5 V. In standard mode, the
battery switch-over works only for V
DD
> 2.5 V.
V
DD
may be lower than V
BAT
(for example V
DD
=3V, V
BAT
=4.1V).
Fig 4. Battery switch-over behavior in standard mode with bit BIE set logic 1 (enabled)
001aaj311
internal power supply (= V
BBS
)
cleared via interface
backup battery operation
BF
V
th(sw)bat
(= 2.5 V)
V
DD
(= 0 V)
V
BAT
V
DD
V
BBS
V
BBS
INT