PCF2127 View Datasheet(PDF) - NXP Semiconductors.
Part Name
Description
MFG CO.
'PCF2127' PDF : 101 Pages View PDF
NXP Semiconductors
PCF2127
Accurate RTC with integrated quartz crystal for industrial applications
8.6.3.2 Extra power fail detection when the battery switch-over function is disabled
If the battery switch-over function is disabled and the power fail comparator is enabled,
the power fail output at pin PFO depends only on the result of the comparison between
VPFI and 1.25 V:
• If VPFI > 1.25 V, PFO = HIGH (through the external pull-up resistor)
• If VPFI < 1.25 V, PFO = LOW
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Fig 13. PFO signal behavior when battery switch-over is disabled
DDM
8.6.4 Battery backup supply
The VBBS voltage on the output pin BBS is at the same potential as the internal operating
voltage Voper(int), depending on the selected battery switch-over function mode:
Table 26. Output pin BBS
Battery switch-over function
mode
Conditions
standard
direct switching
disabled
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
Potential of
Voper(int) and
VBBS
VDD
VBAT
VDD
VBAT
VDD
The output pin BBS can be used as a supply for external devices with battery backup
needs, such as SRAM (see Ref. 3 “AN11266”). For this case, Figure 14 shows the typical
driving capability when VBBS is driven from VDD.
PCF2127
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 8 — 19 December 2014
© NXP Semiconductors N.V. 2014. All rights reserved.
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