WM8310 datasheet(114/291 Pages) WOLFSON

114 / 291 page

WM8310

Pre-Production

PP, May 2012, Rev 3.1

114

17.7.4

CHARGER TIMEOUT AND TERMINATION

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



Charge current falls below the ‘End of Charge’ threshold



Charger timeout



Battery fault or overvoltage condition (see Section 17.7.6)



Chip overtemperature condition (see Section 17.7.2)



Transition to the OFF power state

The End of Charge current threshold can be set using the CHG_ITERM register field, as defined in

Table 59. Charging is terminated when the charge current is below the CHG_ITERM threshold,

provided also that the battery voltage has reached the target voltage CHG_VSEL at the end of the

constant voltage charge phase.

If the battery charger current is reduced or paused due to a drop in SYSVDD voltage (as described in

Section 17.7.1), then the End of Charge current threshold does not cause battery charging to be

terminated, as the charge current is not indicative of the battery charge status in this case.

The battery charger has a programmable safety timer to control the battery charge duration. The timer

is started when either fast charging or trickle charging commences, including charging that is

triggered as a result of the battery voltage dropping to the charger re-start threshold. The timer is re-

started if the charging mode is changed (eg. between fast charge and trickle charge modes). The

timeout period may be set by writing to the CHG_TIME register field; this allows charge times of up to

510mins (8.5 hours) to be selected.

When the timeout period completes, the battery charge cycle is terminated. In this event, the charger

will not re-start until the charger has been disabled (CHG_ENA = 0) and then re-enabled (CHG_ENA

= 1). Note that the charger re-start threshold is ignored in this case, and the charger will not re-start

automatically.

The elapsed battery charge time can be read from the CHG_TIME_ELAPSED register field. This field

is reset whenever the charger timer is started (ie. by starting charging, stopping charging, or changing

charging modes).

If charging is paused due to a battery temperature or chip temperature condition, then the charge

timer is paused until charging resumes.

Battery charging is terminated if removal of the battery is detected via the NTC monitor connections

(see Section 17.7.2).

The register control fields for battery charger termination are described in Table 59. Note that the

Battery Charger control registers are locked by the WM8310 User Key. These registers can only be

changed by writing the appropriate code to the Security register, as described in Section 12.4.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R16456

(4048h)

Charger

Control 1

12:10

CHG_ITERM

[2:0]

000

Battery End of Charge current threshold

000 = 20mA

001 = 30mA

010 = 40mA

011 = 50mA

100 = 60mA

101 = 70mA

110 = 80mA

111 = 90mA

Protected by user key

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