pcf2127a NXP Semiconductors, pcf2127a Datasheet - Page 21

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

NXP Semiconductors
PCF2127A_1
Product data sheet
8.6.3 Battery low detection function
The PCF2127A has a battery low detection circuit which monitors the status of the battery
V
When V
(register Control_3) is set to indicate that the battery is low and that it must be replaced.
Monitoring of the battery voltage also occurs during battery operation.
An unreliable battery can not prevent that the supply voltage drops below V
1.2 V) and therewith the data integrity gets lost.
When V
Figure
1. The battery low flag BLF is set logic 1.
2. An interrupt is generated if the control bit BLIE (register Control_3) is enabled
3. The flag BLF remains logic 1 until the battery is replaced. BLF cannot be cleared
Fig 7.
BAT
(see
using the interface. It is cleared automatically by the battery low detection circuit when
the battery is replaced.
V
.
BBS
(mV)
8):
−200
−400
−600
−800
BAT
BAT
− V
Section
Typical driving capability of V
current I
0
DD
0
drops below the threshold value V
drops below the threshold value V
8.13.7).
BBS
Rev. 01 — 21 January 2010
2
BBS
: (V
4
BBS
th(bat)low
Integrated RTC, TCXO and quartz crystal
th(bat)low
− V
DD
, the following sequence occurs (see
) with respect to the output load
(typically 2.5 V) the BLF flag
6
V
V
V
I
BBS
DD
DD
DD
PCF2127A
= 5 V
= 3 V
= 2 V
(mA)
© NXP B.V. 2010. All rights reserved.
001aaj327
low
8
(typical
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