API9221 datasheet(10/17 Pages) DIODES

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API9221

Car/Wall or USB Supply Input Lithium Battery Charger

with OVP USB Bypass and 10mA LDO

API9221

Document number: DS32204 Rev. 1 - 2

10 of 17

www.diodes.com

May 2010

Functional Description (Continued)

For example, a resistor value of 22k

Ω sets a charge current of 0.31A.

The recommended IUSB setting is 46.5mA to 465mA.

The maximum charge current available may be otherwise limited by the external USB current limit, or by thermal

protection within the API9221.

The rDS(ON) of the FET in the USB charging path is typically 600mΩ at room temperature. At the IUSB limit of

465mA, there is a voltage drop of nearly 0.3V. Therefore, the voltage at the VUSB input must be at least 4.5V to

charge the battery to 4.2V in the minimum time.

The VUSB input is safe from damage up to 28V.

Trickle Charge

When the battery voltage is below the Preconditioning Threshold, VMIN, the charger is in the Trickle Charge state

and the charge current is limited to 18% of the available charge current set by RIVDC or RIUSB. If the USB charge

current is programmed to a value less than the VDC trickle charge, then this value of the USB current is used in

trickle mode (no derating).

When the battery voltage reaches VMIN, the charge current increases to 100% of the available charge current.

End-of-Charge Current

During charging, as the battery voltage approaches the regulated value of 4.2V, the charging current will begin to

decrease. Eventually the charging current settles to a value just low enough to maintain the regulated voltage.

When the current becomes less than the End-of-Charge threshold current, IMIN, the logic output CHG goes HIGH.

The threshold current is set by an external resistor connected between the IMIN and GND pins. This is

independent of whether the VDC or VUSB input is valid.

The resistor at IMIN determines the EOC threshold current according to

IMIN

MIN

550

Amp

For example, a resistor value of 10k

Ω sets the EOC threshold current to 55mA.

Accuracy

When the constant voltage phase has been reached, the battery is charged to 4.2V ±1%. This is the maximum

error over the ambient temperature range from -40°C to +85°C.

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