WM8310 datasheet(110/291 Pages) WOLFSON

110 / 291 page

WM8310

Pre-Production

PP, May 2012, Rev 3.1

110

The battery charger voltage and current are programmable. Trickle charging and fast charging modes

are supported. In both modes, the SYSVDD voltage is monitored to ensure the power supply capacity

or USB current limit is not exceeded. If the SYSVDD voltage drops to 3.9V, (eg. if the USB current

limit has been reached), then the battery charge current is automatically reduced to try and prevent

further voltage drop at SYSVDD.

Under high operating load conditions, the battery may be required to supplement the USB or Wall

Adaptor power sources. Note that this capability is supported even when battery charging is enabled;

in this case, the battery provides power to the system when required, and the charger resumes when

sufficient current capacity is available.

Typical connections for the WM8310 battery charger are illustrated in Figure 25.

WM8310

NTCMON

BATTVDD

GND

LED1

Charge status

indicator LED

charge current

Battery temperature

measurement

Primary power

source

Secondary power

source - used when

primary is unavailable

USBVDD

SYSVDD

NTCBIAS

Battery monitor

source

Single-cell

lithium battery

Main battery

connection

System status

LED output

WALLVDD

WALLFETENA

Wall Adaptor Supply

SYSVDD

Figure 25 Typical Connections for WM8310 Battery Charger

The main battery terminal is connected to BATTVDD. The WM8310 also incorporates a battery

temperature monitoring circuit, which monitors the NTC thermistor that is typically incorporated within

a rechargeable battery pack. The NTCMON pin allows the charger to detect a hot or cold battery

condition that may be outside the battery’s usable operating conditions. Battery removal is also

detected using the NTCMON pin.

The bias resistor connected between NTCBIAS and NTCMON should be a 1% tolerance resistor with

a nominal value equal to the value of the battery’s NTC thermistor at 25

C.

The temperature monitoring circuit can be disabled by shorting NTCMON to LDO12VOUT. This is

only recommended if there is no NTC thermistor incorporated in the battery pack or if battery

temperature monitoring is provided by other methods. Note that the short between NTCMON and

LDO12VOUT is only sensed during start-up; the temperature monitoring circuit cannot be enabled /

disabled dynamically in the ON or SLEEP power states.

See Section 17.7.7 for more details of the battery temperature monitoring function.

A typical battery charge cycle is illustrated in Figure 26. This shows both the trickle charge and fast

charge processes.

The trickle charge mode is a constant current mode. The small charge current in this mode is suitable

for pre-conditioning a deeply discharged battery, or when only limited power is available for battery

charging. When the charger is enabled and the conditions for fast charging are not met, then trickle

charging is selected. (Note that fast charging is not permitted if the battery voltage is below the

defective battery threshold voltage.) Trickle charging is disabled when the charger enters the fast

charging stage, or when the charge current drops to a programmable ‘End of Charge’ threshold level

at the end of the constant voltage charge phase.

WM8310 Datasheet(PDF) 110 Page - Wolfson Microelectronics plc

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