PCF2127AT/1 NXP [NXP Semiconductors], PCF2127AT/1 Datasheet - Page 18

• Manufacturer Part Number: PCF2127AT/1
• Description: Integrated RTC, TCXO and quartz crystal
• Manufacturer: NXP [NXP Semiconductors]

NXP Semiconductors
PCF2127A_2
Product data sheet
8.6.1.1 Standard mode
8.6.1 Battery switch-over function
The PCF2127A has a backup battery switch-over circuit which monitors the main power
supply V
condition is detected.
One of two operation modes can be selected:
V
When a power failure condition occurs and the power supply switches to the battery the
following sequence occurs:
The interface is disabled in battery backup operation:
If V
If V
1. The battery switch flag BF (register Control_3) is set logic 1.
2. An interrupt is generated if the control bit BIE (register Control_3) is enabled
3. If the control bit BTSE (register Control_3) is logic 1, the timestamp registers store the
4. The battery switch flag BF is cleared via the interface; it must be cleared to clear the
th(sw)bat
•
•
•
•
DD
DD
Standard mode: the power failure condition happens when:
V
Direct switching mode: the power failure condition happens when V
Direct switching from V
(see
time and date when the battery switch occurred (see
interrupt.
Interface inputs are not recognized, preventing extraneous data being written to the
device
Interface outputs are high-impedance
DD
> V
< V
DD
< V
is the battery switch threshold voltage. Typical value is 2.5 V.
Section
BAT
BAT
and automatically switches to the backup battery when a power failure
BAT
OR V
AND V
All information provided in this document is subject to legal disclaimers.
AND V
8.13.7).
DD
DD
> V
DD
< V
Rev. 02 — 7 May 2010
th(sw)bat
< V
DD
th(sw)bat
th(sw)bat
to V
the internal power supply is V
BAT
the internal power supply is V
without requiring V
Integrated RTC, TCXO and quartz crystal
DD
Section
to drop below V
DD
BAT
8.12.4).
.
PCF2127A
.
© NXP B.V. 2010. All rights reserved.
DD
th(sw)bat
< V
BAT
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