pcf2127a NXP Semiconductors, pcf2127a Datasheet - Page 17

• Manufacturer Part Number: pcf2127a
• Description: Integrated Rtc, Tcxo And Quartz Crystal
• Manufacturer: NXP Semiconductors

NXP Semiconductors
PCF2127A_1
Product data sheet
8.6.1 Battery switch-over function
Table 17.
[1]
[2]
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:
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:
PWRMNG[2:0]
011
100
101
110
111
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
•
•
•
Default value.
When the battery switch-over function is disabled, the PCF2127A works only with the power supply V
V
Standard mode: the power failure condition happens when:
V
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
BAT
DD
th(sw)bat
must be put to ground and the battery low detection function is disabled.
DD
< V
Section
Power management control bit description
and automatically switches to the backup battery when a power failure
BAT
is the battery switch threshold voltage. Typical value is 2.5 V.
AND V
[2]
[2]
8.13.6).
Function
battery switch-over function is enabled in direct switching mode;
battery low detection function is enabled;
extra power fail detection function is enabled
battery switch-over function is enabled in direct switching mode;
battery low detection function is disabled;
extra power fail detection function is enabled
battery switch-over function is enabled in direct switching mode;
battery low detection function is disabled;
extra power fail detection function is disabled
battery switch-over function is disabled - only one power supply (V
battery low detection function is disabled;
extra power fail detection function is enabled
battery switch-over function is disabled - only one power supply (V
battery low detection function is disabled;
extra power fail detection function is disabled
Rev. 01 — 21 January 2010
DD
< V
DD
th(sw)bat
to V
BAT
without requiring V
Integrated RTC, TCXO and quartz crystal
…continued
DD
Section
to drop below V
8.12.4).
PCF2127A
© NXP B.V. 2010. All rights reserved.
DD
th(sw)bat
< V
DD
DD
BAT
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