PCA2129T/Q900/2,51 NXP Semiconductors, PCA2129T/Q900/2,51 Datasheet - Page 19

• Manufacturer Part Number: PCA2129T/Q900/2,51
• Description: Real Time Clock
• Manufacturer: NXP Semiconductors
• Series: PCA2129r

Specifications of PCA2129T/Q900/2,51

• Rohs: yes
• Function: Clock, Calendar, Alarm, Watchdog, Timestamp
• Rtc Bus Interface: I2C, SPI
• Date Format: Binary
• Time Format: Binary
• Supply Voltage - Max: 4.2 V
• Supply Voltage - Min: 1.8 V
• Maximum Operating Temperature: + 80 C
• Minimum Operating Temperature: - 30 C
• Mounting Style: SMD/SMT
• Package / Case: SOP-16
• Battery Backup Switching: Yes

NXP Semiconductors
PCA2129T
Product data sheet
8.5.3 Battery low detection function
The output pin BBS can be used as a supply for external devices with battery backup
needs, such as SRAM (see
driving capability when V
The PCA2129T 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 cannot prevent that the supply voltage drops below V
1.2 V) and with that 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 by
Fig 8.
BAT
V
DD
V
(see
command. It is cleared automatically by the battery low detection circuit when the
battery is replaced.
(= 2.5 V)
th(bat)low
.
= V
V
8):
BLF
BBS
INT
BAT
BAT
BAT
Section
Battery low detection behavior with bit BLIE set logic 1 (enabled)
drops below the threshold value V
drops below the threshold value V
All information provided in this document is subject to legal disclaimers.
8.12.7).
Rev. 3 — 24 January 2013
BBS
Accurate RTC with integrated quartz crystal for automotive
Ref. 3
is driven from V
“AN11120”). For this case,
internal power supply (= V
DD
th(bat)low
th(bat)low
.
V
BAT
, the following sequence occurs (see
(typically 2.5 V), the BLF flag
BBS
)
Figure 7
PCA2129T
shows the typical
© NXP B.V. 2013. All rights reserved.
low
(typical
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