pcf2129a NXP Semiconductors, pcf2129a Datasheet - Page 14

• Manufacturer Part Number: pcf2129a
• Description: Integrated Rtc, Tcxo And Quartz Crystal
• Manufacturer: NXP Semiconductors

NXP Semiconductors
PCF2129A_1
Product data sheet
8.5.1 Battery switch-over function
8.5 Power management functions
The PCF2129A has two power supply pins and one power output pin:
The PCF2129A has two power management functions implemented:
The power management functions are controlled by the control bits PWRMNG[2:0] in
register Control_3:
Table 13.
[1]
[2]
The PCF2129A 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
PWRMNG[2:0]
000
001
010
011
100
101
111
th(sw)bat
•
•
•
•
•
•
•
V
V
BBS - battery backed output voltage pin (equal to the internal power supply)
Battery switch-over function
Battery low detection function
Default value.
When the battery switch-over function is disabled, the PCF2129A works only with the power supply V
V
Standard mode: the power failure condition happens when:
V
Direct switching mode: the power failure condition happens when V
Direct switching from V
BAT
DD
BAT
DD
must be put to ground and the battery low detection function is disabled.
- the main power supply input pin
DD
< V
is the battery switch threshold voltage. Typical value is 2.5 V.
- the battery backup input pin
Power management control bit description
and automatically switches to the backup battery when a power failure
BAT
AND V
[1]
[2]
Function
battery switch-over function is enabled in standard mode;
battery low detection function is enabled
battery switch-over function is enabled in standard mode;
battery low detection function is disabled
battery switch-over function is enabled in standard mode;
battery low detection function is disabled
battery switch-over function is enabled in direct switching mode;
battery low detection function is enabled
battery switch-over function is enabled in direct switching mode;
battery low detection function is disabled
battery switch-over function is enabled in direct switching mode;
battery low detection function is disabled
battery switch-over function is disabled, only one power supply (V
battery low detection function is disabled
Rev. 01 — 13 January 2010
DD
< V
DD
th(sw)bat
to V
BAT
without requiring V
Integrated RTC, TCXO and quartz crystal
DD
to drop below V
PCF2129A
© NXP B.V. 2010. All rights reserved.
DD
th(sw)bat
< V
DD
BAT
);
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DD
;