PCF2129T View Datasheet(PDF) - NXP Semiconductors.
Part Name
Description
MFG CO.
'PCF2129T' PDF : 73 Pages View PDF
NXP Semiconductors
PCF2129T
Accurate RTC with integrated quartz crystal for industrial
8.5.1.4 Battery switch-over architecture
The architecture of the battery switch-over circuit is shown in Figure 6.
comparators
Vth(sw)bat
VDD
Vth(sw)bat
VBAT
VCC
VCC
logic
LOGIC
VDD
VDD(int)
VBAT
switches
VDD(int)
VDD(int)
Fig 6. Battery switch-over circuit, simplified block diagram
VBBS
(internal
power supply)
001aag061
The internal power supply (available on pin BBS) is equal to VDD or VBAT. It has to be
assured that there are decoupling capacitors on the pins VDD, VBAT, and BBS.
8.5.2 Battery backup supply
The VBBS voltage on the output pin BBS is equal to the internal power supply, depending
on the selected battery switch-over function mode:
Table 15. Output pin BBS
Battery switch-over function mode
standard
direct switching
disabled
Conditions
VDD > VBAT OR VDD > Vth(sw)bat
VDD < VBAT AND VDD < Vth(sw)bat
VDD > VBAT
VDD < VBAT
only VDD available,
VBAT must be put to ground
VBBS equals
VDD
VBAT
VDD
VBAT
VDD
PCF2129T
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 3 — 12 February 2013
© NXP B.V. 2013. All rights reserved.
18 of 73
Share Link: 
