AS3722 datasheet(47/199 Pages) AMSOSRAM

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[v1-01] 2015-Sep-07

AS3722 − Detailed Descriptions- Power Management Functions

Backup Battery Charger

Description

The backup battery charger operates as a programmable

voltage limited current source with a selectable output resistor.

It is enabled by setting BBCMode in the Backup Battery Charger

features:

• Backup battery presence detection

• Selectable output resistor (RBBCOUT) to reduce the current

at higher voltages

• Programmable charge current IBBC

• Programmable maximum charging voltage VBBC

• Reverse current protection turns off backup battery

charger automatically if VSUP<VVBAT_BKUP; as soon as VSUP

exceeds VVBAT_BKUP charging is started again

automatically

• Charging is stopped automatically as soon as the backup

battery is fully charged; if the voltage on pin VBAT_BKUP

drops charging is started again automatically

• In case the main supply voltage VSUP or VBAT is larger than

VBAT_BKUP charging of the backup battery is possible in

state “Off ” as well; the device will check VVBAT_BKUP every

minute to determine if charging is required.

Figure 46:

Backup Battery Charger Block Diagram

Backup Battery Charger Block Diagram: Shows the internal structure of the charger for the backup battery.

Voltage limited

Current Source

VBAT_BKUP

Digital Control

VSUP

AS3722 Datasheet(PDF) 47 Page - ams-OSRAM AG