PCF2129AT/1,512 NXP Semiconductors, PCF2129AT/1,512 Datasheet - Page 19

• Manufacturer Part Number: PCF2129AT/1,512
• Description: IC REAL TIME CLK/CALENDAR 20SOIC
• Manufacturer: NXP Semiconductors
• Type: Clock/Calendar/Alarmr

Specifications of PCF2129AT/1,512

• Package / Case: 20-SOIC (7.5mm Width)
• Date Format: YY-MM-DD-dd
• Time Format: HH:MM:SS (12/24 hr)
• Interface: I²C, SPI
• Voltage - Supply: 1.8 V ~ 4.2 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Function: Clock, Alarm, Watchdog, Timestamp
• Supply Voltage (max): 4.2 V
• Supply Voltage (min): 1.8 V
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Mounting Style: SMD/SMT
• Rtc Bus Interface: I2C, SPI
• Supply Current: 800 uA
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Memory Size: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: 568-4960-5; 935288599512

NXP Semiconductors
PCF2129A_2
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 PCF2129A 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 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 8.
BAT
V
DD
V
(see
using the interface. 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. 02 — 7 May 2010
BBS
Ref. 3
is driven from V
“AN10857”). For this case,
internal power supply (= V
DD
th(bat)low
Integrated RTC, TCXO and quartz crystal
th(bat)low
.
V
BAT
, the following sequence occurs (see
(typically 2.5 V) the BLF flag
BBS
)
Figure 7
PCF2129A
shows the typical
© NXP B.V. 2010. All rights reserved.
low
(typical
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