Datasheet

Product data sheet Rev. 6 — 17 September 2013 54 of 78

NXP Semiconductors

PCF8523

Real-Time Clock (RTC) and calendar

• in the range of a few hundreds of A, the value of the capacitor on pin V

must be

increased to force a falling gradient of less than 0.7 V/ms on pin V

to assure the

proper functionality of the battery switch-over

• higher than some mA it is recommended to add an RC network on the V

pin, as

shown in Figure 37

A series resistor of 1 k and a capacitor of 3.3 F assure the proper functionality of the

battery switch-over even with very fast V

slope.

Note that:

• it is not suggested to assemble a series resistor higher than 2.2 k because of the

associated voltage drop

• lower values of capacitors are possible, depending on the V

slope in the

application.

3. Like in the case of no interface activity and/or early power fail detection functions that allow the microcontroller to perform early

backup operations and to set power-down modes.

4. Like in the case of interface activity.

5. Like in the case where an additional circuity is supplied from V

Fig 37. RC network on pin V

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