WM8351 datasheet(162/330 Pages) WOLFSON

162 / 330 page

WM8351

Production Data

PD, April 2012, Rev 4.5

162

17.7.5

BATTERY CHARGER TIMEOUT AND TERMINATION

Fast charging and Trickle charging is terminated under any of the following conditions:



Charge current falls below a programmable threshold



Charger timeout



Charger fault condition (see Section 17.7.7)

The End of Charge Current threshold can be set between 20mA and 90mA, using the

CHG_EOC_SEL register field, as defined in Table 107. Care should be taken to ensure that the End

of Charge Threshold is lower than the selected Charge Current Limit (CHG_ISEL and/or

CHG_TRICKLE_SEL).

When the End of Charge Current threshold is reached, the CHG_END_EINT interrupt field is set (see

Section 17.7.8). The action taken when the End of Charge Current threshold occurs is set by

CHG_END_ACT. The battery charging will either be terminated or will continue until timeout.

When Trickle charge choking or Fast charge throttling is enabled, it is possible that these circuits may

cause the charge current to be reduced below the CHG_EOC_SEL threshold even though the battery

is not fully charged. When choke or throttle control is enabled, the End of Charge detection described

above is disabled, and charging always continues until timeout. It is recommended that Trickle charge

choking and Fast charge throttling is enabled.

The WM8351 battery charger has a programmable timer. The timer is initiated when either fast

charging or trickle charging commences. The initial value of the timer may be set by writing to the

CHG_TIME register field. This field can also be read back as an indicator of the charge time

remaining. Note that the readback value of this field is coded differently to the write value. Due to the

limited resolution provided by the 4-bit field, the readback value is approximate only, to an accuracy of

around 35 minutes.

If charging is paused by setting CHG_PAUSE (see Table 104), or is paused due to temperature or

maximum current conditions, the charge timer is halted so that the time limit is extended accordingly.

If the charging mode is changed by asserting or de-asserting CHG_FAST, then the timer is reset to its

initial value.

If the charging mode reverts to Trickle charge mode as a result of a change in power source or a

change in USB power mode, then the timer is not reset, but continues to count down from its earlier

value. (Note that the charger will never autonomously switch from Trickle charge mode to Fast charge

mode.)

When the Charger Timer completes, the CHG_TO_EINT interrupt field is set (see Section 17.7.8) and

charging is terminated.

WM8351 Datasheet(PDF) 162 Page - Wolfson Microelectronics plc