WM8352 datasheet(159/336 Pages) WOLFSON

159 / 336 page

Production Data

WM8352

PD, February 2011, Rev 4.4

159

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)

Power Mgmt

(5)

CHG_ENA

CHG_ENA bit selects battery charger

current control

0 = Set battery charger current to zero

1 = Enable battery charge control

Protected by security key.

R168 (A8h)

Battery charger

control 1

R169 (A9h)

Battery charger

control 2

CHG_ACTIVE

Charger Status.

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).

CHG_PAUSE

Charger pause:

0 = Don't pause the charger

1 = Pause charging

5:4

CHG_VSEL

[1:0]

Battery charge voltage:

00 = 4.05V

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

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.

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