PCF2127T Ver la hoja de datos (PDF) - NXP Semiconductors.
Número de pieza
componentes Descripción
Fabricante
PCF2127T Datasheet PDF : 101 Pages
| |||
NXP Semiconductors
PCF2127
Accurate RTC with integrated quartz crystal for industrial applications
8.6.1 Battery switch-over function
The PCF2127 has a backup battery switch-over circuit which monitors the main power
supply VDD. When a power failure condition is detected, it automatically switches to the
backup battery.
One of two operation modes can be selected:
Standard mode — the power failure condition happens when:
VDD < VBAT AND VDD < Vth(sw)bat
Vth(sw)bat is the battery switch threshold voltage. Typical value is 2.5 V. The battery
switch-over in standard mode works only for VDD > 2.5 V
Direct switching mode — the power failure condition happens when VDD < VBAT. Direct
switching from VDD to VBAT without requiring VDD to drop below Vth(sw)bat
When a power failure condition occurs and the power supply switches to the battery, the
following sequence occurs:
1. The battery switch flag BF (register Control_3) is set logic 1.
2. An interrupt is generated if the control bit BIE (register Control_3) is enabled
(see Section 8.13.7).
3. If the control bit BTSE (register Control_3) is logic 1, the timestamp registers store the
time and date when the battery switch occurred (see Section 8.12.4).
4. The battery switch flag BF is cleared by command; it must be cleared to clear the
interrupt.
The interface is disabled in battery backup operation:
• Interface inputs are not recognized, preventing extraneous data being written to the
device
• Interface outputs are high-impedance
For further information about I2C-bus communication and battery backup operation, see
Section 9.3 on page 70.
PCF2127
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 8 — 19 December 2014
© NXP Semiconductors N.V. 2014. All rights reserved.
19 of 100
Share Link: 