WM8311GEB/V Wolfson Microelectronics, WM8311GEB/V Datasheet - Page 107

• Manufacturer Part Number: WM8311GEB/V
• Description: POWER MANAGEMENT SUBSYSTEM, 121BGA
• Manufacturer: Wolfson Microelectronics

Specifications of WM8311GEB/V

• Supply Voltage: 5.5V
• No. Of Step-down Dc - Dc Converters: 4
• No. Of Ldo Regulators: 7
• Digital Ic Case Style: BGA
• No. Of Pins: 121
• No. Of Regulated Outputs: 9
• Operating Temperature Range: -40°C To
• Rohs Compliant: Yes
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

Pre-Production
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Figure 25 Typical Connections for WM8311 Battery Charger
The main battery terminal is connected to BATTVDD. The WM8311 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.
The fast charge mode is also a constant current mode, but higher charge currents are possible in this
mode. In the fast charge phase, the WM8311 drives a programmable constant current into the
battery through the BATTVDD pin. During this phase, the battery voltage rises until the battery
reaches the target voltage.
When the battery reaches the target voltage (through trickle charge and/or fast charge), the charger
enters the constant voltage charge phase, in which the WM8311 regulates BATTVDD to the target
voltage. During this phase of the charge process, the charge current decreases over time as the
battery approaches its fully charged state. Battery charging is terminated when the current falls to a
programmable ‘End of Charge’ threshold level at the end of the constant voltage charge phase.
PP, December 2009, Rev 3.0
WM8311
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