Production Data
WM8352
17.7.2 BATTERY CHARGER ENABLE
The battery charger is enabled by default when the WM8352 is in the ACTIVE, HIBERNATE or OFF
states. Note that battery charging is only possible when the selected power source is within normal
operating limits (see Section 7.5) and is more than 100mV higher than the battery voltage.
The battery charger can be disabled by setting the CHG_ENA register bit to ‘0’. When the battery
charger is enabled, it autonomously checks if the conditions for charging are fulfilled and controls the
charging processes accordingly. The status of the battery charger can be read from the
CHG_ACTIVE register bit. (Note this bit is read-only.)
The battery charger can be paused by writing to the CHG_PAUSE register bit. This provides a simple
option to halt the battery charger and to subsequently restart it without affecting the charge timer or
other settings.
The battery charger target voltage is set by the CHG_VSEL field, as defined in Table 104.
ADDRESS
BIT
LABEL
DEFAULT
DESCRIPTION
R12 (0Ch)
9
CHG_ENA
1
CHG_ENA bit selects battery charger
current control
Power Mgmt
(5)
0 = Set battery charger current to zero
1 = Enable battery charge control
Protected by security key.
R168 (A8h)
15
15
Battery charger
control 1
R169 (A9h)
CHG_ACTIVE
CHG_PAUSE
0
Charger Status.
Battery charger
control 2
0 = Battery Charging is inactive
1 = Battery Charging is active
(Note CHG_ENA is just a request; the
WM8352 determines if the conditions are
satisfied for Battery Charging).
14
0
Charger pause:
0 = Don't pause the charger
1 = Pause charging
Battery charge voltage:
00 = 4.05V
5:4
CHG_VSEL
[1:0]
00
01 = 4.1V
10 = 4.15V
11 = 4.2V
Note: CHG_ENA can be accessed through R9 or through R168. Reading from or writing to either
register location has the same effect.
Table 104 Battery Charger Control
17.7.3 TRICKLE CHARGING
Trickle charging is enabled by default when the Wall (LINE) or USB pins are selected as the power
source. It is autonomously initiated, supervised and terminated by the WM8352, without requiring any
intervention by the host processor.
By default, trickle charging is initiated when the battery voltage is below the battery charge voltage
CHG_VSEL by more than 100mV. Setting the CHG_FRC bit allows trickle charging to be initiated at
higher battery voltages.
The trickle charge current is set by the CHG_TRICKLE_SEL field, as described in Table 105.
A choke circuit is provided to enhance the trickle charge current control. This allows the charge
current to be modified according to temperature conditions or according to the USB current limit
restrictions.
If the WM8352 temperature is above 115°C and trickle charge temperature choking is enabled, then
charging is interrupted for at least 8 seconds and until the temperature has fallen below the
threshold. If trickle charge temperature choking is not enabled, then charging continues. (Note that
the device shutdown temperature is set at 140°C - this threshold cannot be disabled.) Trickle charge
temperature choking is controlled by the CHG_TRICKLE_TEMP_CHOKE register bit.
PD, February 2011, Rev 4.4
159
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WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
