Datasheet

PCF2129 All information provided in this document is subject to legal disclaimers. © NXP Semiconductors N.V. 2014. All rights reserved.
Product data sheet Rev. 7 — 19 December 2014 19 of 86
NXP Semiconductors
PCF2129
Accurate RTC with integrated quartz crystal for industrial applications
8.5.1.2 Direct switching mode
If V
DD
> V
BAT
: V
oper(int)
is at V
DD
potential.
If V
DD
< V
BAT
: V
oper(int)
is at V
BAT
potential.
The direct switching mode is useful in systems where V
DD
is always higher than V
BAT
.
This mode is not recommended if the V
DD
and V
BAT
values are similar (for example,
V
DD
= 3.3 V, V
BAT
 3.0 V). In direct switching mode, the power consumption is reduced
compared to the standard mode because the monitoring of V
DD
and V
th(sw)bat
is not
performed.
8.5.1.3 Battery switch-over disabled: only one power supply (V
DD
)
When the battery switch-over function is disabled:
• The power supply is applied on the V
DD
pin
• The V
BAT
pin must be connected to ground
• V
oper(int)
is at V
DD
potential
• The battery flag (BF) is always logic 0
Fig 7. Battery switch-over behavior in direct switching mode with bit BIE set logic 1
(enabled)
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