WM8310 datasheet(113/291 Pages) WOLFSON

113 / 291 page

Pre-Production

WM8310

PP, May 2012, Rev 3.1

113

17.7.3

FAST CHARGING

Fast charging provides a faster way to charge the battery than is possible with trickle charge. See

Section 17.7.1 for a description of fast charging.

Fast charging mode is only possible under certain conditions. It is only possible when the selected

power source is Wall or when the USB current limit is set to 500mA or more. It is also required that

the battery voltage is above the fast charge voltage threshold; this ensures that fast charging is not

applied to a heavily discharged battery.

Fast charging is enabled by setting the CHG_FAST register bit, provided that the conditions for fast

charging are satisfied. The fast charge current limit is selected using the CHG_FAST_ILIM field.

The battery charge current is automatically controlled, up to a maximum set by CHG_FAST_ILIM. The

current is automatically limited when required if the battery is fully charged, or if the system supply,

SYSVDD, drops as described in Section 17.7.1.

The fast charge mode comprises two phases, as described in Section 17.7.1. When the charger is in

the constant voltage charge phase, the CHG_TOPOFF bit will be set to indicate that the charge is

approaching completion.

When the battery reaches the target voltage, the charger enters the constant voltage charge phase, in

which the WM8310 regulates BATTVDD to the target voltage. When the charger is in the constant

voltage charge phase, then the CHG_TOPOFF bit will be set (see Section 17.7.2) to indicate that the

charge is approaching completion.

The register control fields for fast charging are described in Table 58. 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

CHG_FAST

Battery Fast Charge Enable

0 = Disable

1 = Enable

Protected by user key

R16457

(4049h)

Charger

Control 2

3:0

CHG_FAST_ILIM

[3:0]

0010

Battery Fast Charge current limit

0000 = 0mA

0001 = 50mA

0010 = 100mA

0011 = 150mA

0100 = 200mA

0101 = 250mA

0110 = 300mA

0111 = 350mA

1000 = 400mA

1001 = 450mA

1010 = 500mA

1011 = 600mA

1100 = 700mA

1101 = 800mA

1110 = 900mA

1111 = 1000mA

Protected by user key

Table 58 Fast Charge Control

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