WM8352 datasheet(153/336 Pages) WOLFSON

153 / 336 page

Production Data

WM8352

PD, February 2011, Rev 4.4

153

HIVDD is an external connection which exists for the purposes of decoupling only. It represents the

highest available power supply connected to the WM8352. It should be noted that the preferred

supply (on the LINE pin) is not necessarily the same voltage as HIVDD - the Wall supply will always

be the preferred voltage when it is within the intended limits, even if it is not also the highest available

source.

The main battery connects directly to the BATT pin. When the battery is the preferred supply source,

this pin is an input. When battery charging is in operation, this pin is an output. (Note that the backup

VRTC battery is connected separately - see Section 17.6.)

The USB interface connects directly to the USB pin. In USB Master Mode (USB is less than LINE),

the WM8352 can supply power to external devices on this pin. In USB Slave Mode (USB is greater

than LINE), the WM8352 can use this pin as an input to power the device and/or to charge a battery

connected to the BATT pin. Note that, when USB is the preferred power supply, the Battery may also

be used if necessary to supplement the current drawn from the USB pin (ie. to source current into

LINE when required).

All loads connected to the WM8350 should normally be connected to the LINE pin. The inputs to the

DC-DC Converters and LDOs should be connected to the LINE pin. It is not recommended to

connect any load directly to the battery (BATT).

Note that the inputs to the LDOs may be connected to the outputs of the DC-DCs if desired.

17.2 BATTERY POWERED OPERATION

The WM8352 selects battery power when the Battery voltage is higher than the Wall (LINE) and USB

supplies. In practical usage, this means the Battery is used when Wall (LINE) and USB are both

disconnected.

The battery can also be used to supplement the USB supply when required (ie. to source current into

LINE).

If the Wall (LINE) or USB supply becomes available during battery operation, then the selected

power source is adjusted accordingly.

Battery pack temperature sensing is enabled by default. The battery’s NTC resistor is monitored via

the AUX1 pin on the WM8352, as described in Section 17.7. Note that the absence of this NTC

connection will lead to a temperature failure condition being detected and battery charging will not be

possible.

Safe operation of the battery charger outside the designed operating temperatures is not guaranteed

when a battery NTC resistor is not used. The designed operating temperatures are noted in

Section 17.7.7.

17.3 WALL ADAPTOR (LINE) POWERED OPERATION

The WM8352 selects Wall Adaptor power via the LINE pins whenever the Wall Adaptor supply is

within the normal operating limits of 4.0V to 5.5V. The Wall Adaptor is also selected as the power

source below 4.0V in the case where it is the highest available power source. The minimum LINE

voltage is a programmable threshold in the range 2.9V to 3.6V (see Section 18). The maximum

recommended operating voltage for LINE is 5.5V.

Note that USB power is not used when a suitable LINE supply is available, even if the USB supply is

higher than the Wall (LINE) supply.

If the Wall (LINE) supply becomes unsuitable and a USB is available, then the USB supply will be

selected as the preferred power source. Note that, when hot-swapping from Wall (LINE) to USB

supply, a usable Battery must be present on the BATT pin.

When the Wall (LINE) supply is selected and a Battery is connected, then trickle charging is enabled

by default, including when the WM8352 is in the OFF or HIBERNATE states. When the WM8352 is

in the ACTIVE state, then fast charging may be selected under software control.

WM8352 Datasheet(PDF) 153 Page - Wolfson Microelectronics plc

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