PCF85263ATTSLASHA datasheet(49/100 Pages) NXP

49 / 100 page

PCF85263A

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Product data sheet

Rev. 4.1 — 27 November 2015

49 of 100

NXP Semiconductors

PCF85263A

Tiny RTC with alarm, battery switch-over, and I2C-bus

8.11.3.4

Switching at the lower of VBAT and Vth level, BSM[1:0] = 11

With this mode switching takes place when VDD falls below the lower of Vth or VBAT. In

Figure 27, an example is given where the threshold is set to 1.5 V and a single cell battery

is connected to VBAT. In this example, switching to the battery voltage takes place when

VDD falls below VBAT.

8.11.4 BSTH: threshold voltage control

[1]

Default value.

The threshold for battery switch-over is selectable between two voltages, 1.5 V and 2.8 V.

8.11.5 Battery switch interrupts

The generation of interrupts from the battery switch function is controlled via the battery

switch interrupt enable bits; BSIEA and BSIEB. These bits are in registers INTA_enable

(address 29h) and INTB_enable (address 2Ah).

The assertion of the flag BSF (register Flags, address 2Bh) can be used to generate an

interrupt at pins INTA and INTB. The interrupt may be generated as a pulsed signal or

alternatively as a permanently active signal which follows the condition of bit BSF. BSF

remains set until cleared by command.

Fig 27. Switching at the lower of VBAT or Vth

Table 42.

BSTH - battery switch control (address 26h) bit description

Bit

Symbol

Value

Description

BSTH

battery switch threshold voltage, Vth

0[1]

Vth = 1.5 V

1Vth = 2.8 V

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