PCF2129AT/2,518 NXP Semiconductors, PCF2129AT/2,518 Datasheet - Page 18

• Manufacturer Part Number: PCF2129AT/2,518
• Description: Real Time Clock
• Manufacturer: NXP Semiconductors
• Series: PCF2129r

Specifications of PCF2129AT/2,518

• 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: 1.2 V
• Maximum Operating Temperature: + 60 C
• Minimum Operating Temperature: - 15 C
• Mounting Style: SMD/SMT
• Package / Case: SOP-20
• Battery Backup Switching: Yes
• Factory Pack Quantity: 2000

NXP Semiconductors
PCF2129AT
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 PCF2129AT 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 7.
(see
command. 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
BAT
Section
Typical driving capability of V
current I
0
DD
0
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).
BBS
Rev. 5 — 12 February 2013
BBS
2
Ref. 3
is driven from V
“AN10857”). For this case,
BBS
: (V
4
BBS
DD
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
Figure 7
V
PCF2129AT
V
V
DD
I
BBS
DD
DD
= 4.2 V
= 3 V
= 2 V
(mA)
shows the typical
© NXP B.V. 2013. All rights reserved.
001aaj327
low
8
(typical
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