PC8523-1 데이터 시트보기 (PDF) - NXP Semiconductors.

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PC8523-1

Real-Time Clock (RTC) and calendar

NXP Semiconductors. 

NXP Semiconductors

PCF8523

Real-Time Clock (RTC) and calendar

8.5.2.2 Direct switching mode

If VDD > VBAT the internal power supply is VDD.

If VDD < VBAT the internal power supply is VBAT.

The direct switching mode is useful in systems where VDD is higher than VBAT at all times

(for example, VDD = 5 V, VBAT = 3.5 V). If the VDD and VBAT values are similar (for

example, VDD = 3.3 V, VBAT  3.0 V), the direct switching mode is not recommended. In

direct switching mode, the power consumption is reduced compared to the standard mode

because the monitoring of VDD and Vth(sw)bat is not performed.

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DDD

Fig 10. Battery switch-over behavior in direct switching mode and with bit BSIE set

logic 1 (enabled)

8.5.2.3 Battery switch-over disabled, only one power supply (VDD)

When the battery switch-over function is disabled:

• The power supply is applied on the VDD pin

• The VBAT pin must be connected to VDD

• The battery flag (BSF) is always logic 0

8.5.3 Battery low detection function

The PCF8523 has a battery low detection circuit, which monitors the status of the battery

VBAT.

Generation of interrupts from the battery low detection is controlled via bit BLIE (register

Control_3). If BLIE is enabled, the INT1 follows the status of bit BLF (register Control_3).

When VBAT drops below the threshold value Vth(bat)low (typically 2.5 V), the BLF flag

(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.

PCF8523

Product data sheet

All information provided in this document is subject to legal disclaimers.

Rev. 7 — 28 April 2015

© NXP Semiconductors N.V. 2015. All rights reserved.

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