AS3715 datasheet(44/160 Pages) AMSCO

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ams Datasheet, Confidential

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[v1-00] 2014-Sep-10

AS3715 − Detailed Description – Power Management Functions

Charging Cycle Description

Charge Adapter Detection

The charge controller uses an integrated detection circuit to

determine if an external charge adapter has been applied to

the VUSB pin. If the adapter voltage exceeds the battery voltage

at pin VBAT by VCHDET the ChDet bit in the ChargerStatus

controller (bit ChDet is cleared) as soon as the voltage at the

VUSB pin drops to only VCHMIN above the battery voltage. In

case the AS3715 device is reset the charge controller will also

be reset, even if a charge adapter is applied to the VUSB pin.

Soft Charging

Soft charge mode is started when an external charge adapter

has been detected, the bat_charging_enable is set and the

battery voltage at pin VBAT is below the VSOFT threshold.

Low Current (Trickle) Charging

Trickle charge mode is started when an external charge adapter

has been detected bat_charging_enable is set and the battery

voltage at pin VBAT is below the VTRICKLE threshold and above

VSOFT threshold; bits ChDet and Trickle will be set in the

ChargerStatus register. In this mode the charge current will be

limited to TrickleCurrent (set in the ChargerCurrent register) to

prevent undue stress in case of deeply discharged batteries.

Once VTRICKLE has been exceeded, the charger will change over

to constant current charging (Trickle is cleared).

Constant Current Charging

Constant current charging is initiated when

bat_charging_enable is set and the battery voltage at pin VBAT

is above the VTRICKLE and below VCHOFF. The CCM bit is set when

the charger has started, and the charge current will be limited

to ConstatntCurrent by the battery charge controller. When the

battery approaches full charge, its voltage will reach the charge

termination threshold VCHOFF. VCHOFF depends on the

ChVoltEOC bits settings. Top-off charge will be started (CVM will

be set).

Constant Voltage Charging

Constant voltage charge mode is initiated and the CVM bit will

be set when the VCHOFF threshold has been reached.

The charge current is monitored during constant voltage

charging. It will be decreasing from its initial value during

constant current charging and eventually drop below the value

set by TrickleCurrent. If the measured charge current is less than

or equal to TrickleCurrent, the charging cycle is terminated and

EOC is set.

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