Production Data
WM8352
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 WM8352 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.
ADDRESS
BIT
LABEL
DEFAULT
DESCRIPTION
R168 (A8h)
12:10
CHG_EOC_SE
L [1:0]
000
Selects what the end of charge current
should be set to
Battery charger
control 1
000 = 20mA
001 = 30mA
(10mA steps)
...
111 = 90mA
Protected by security key.
Action to take when charging ends:
0 = Set charge current to 0
6
CHG_END_AC
T
0
1 = Do nothing (leave charger on till
timeout)
Protected by security key
PD, February 2011, Rev 4.4
163
w
WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
