Diodes API9221 Manuel d'utilisateur télécharger pdf (Page 9)

API9221

R/WALL or USB SUPPLY INPUT LITHIUM BATTERY

CHARGER with OVP USB BYPASS and 10mA LDO

API9221

Document number: DS32204 Rev. 2 - 2

9 of 15

www.diodes.com

November 2011

NEW PRODUCT

Functional Characteristics (cont.)

Charging from Adapter Power (VDC pin) (cont.)

The maximum charge current available may be otherwise

limited by the car/wall adapter current limit, by thermal

protection within the API9221, or by the r

DS(ON)

of the

FET in the VDC charging path. For example, if IVDC is

set to 1A, there is a voltage drop of 0.6V due the typical

DS(ON)

of 600m at room temperature. Therefore, the

voltage at the VDC input must be at least 4.8V to charge

the battery to 4.2V in the minimum time.

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

Charging from USB Power (VUSB pin)

The battery can be charged at a current of up to 0.5A

from this pin. In this case the maximum available charge

current is set by an external resistor R

IUSB

connected

between the IUSB and GND pins. If VUSB is greater than

the power-on threshold voltage (VPO

) and less than the

over-voltage protection threshold (OVP

VUSB

), the battery

will begin to charge at a rate dependent on the battery

voltage.

The resistor R

IUSB

resistor determines the charge current

according to

IUSB

6820

IUSB =

Amp

For example, a resistor value of 22k 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 R

DS(ON)

of the FET in the USB charging path is

typically 600m 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, V

MIN

, the charger is in the Trickle Charge

state and the charge current is limited to 18% of the

available charge current set by R

IVDC

or R

IUSB

. 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 V

MIN

, 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, I

MIN,

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

I = Amp

For example, a resistor value of 10k 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.

Fault Summary and Protection

Overvoltage protection: If VDC is greater than OVP

VDC

(6.9V), the VDC charging path is turned off until VDC falls

below OVP

VDC

- HOVP

VDC

, where HOVP

VDC

is the OVP

hysteresis. Similarly, if VUSB is greater than OVP

VUSB

(5.4V), the USB charging path is turned off until VUSB

falls below OVP

VUSB

– HOVP

VUSB

USB_BYP current limit: The USB_BYP load current is

limited to 400mA (nominally).

USB_BYP reverse blocking: If the voltage at USB_BYP

is greater than VUSB, the USB bypass path is turned off.

BAT reverse blocking: If the battery voltage is greater

than either VDC or VUSB, the relevant charge path is

turned off.

VDC_LDO reverse blocking: If the voltage at VDC_LDO

is greater than VDC, the linear regulator is turned off.

Thermal protection: When the junction temperature

reaches 125°C, a current foldback circuit is activated.

This effectively limits the power dissipation to a safe

level.

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Diodes API9221 Manuel d'utilisateur Page 9

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