MP2676 –LI-ION CHARGER PROTECTION IC WITH INTEGRATED P-MOSFET

MP2676 Rev. 0.91

www.MonolithicPower.com

9

12/7/2010

MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.

© 2010 MPS. All Rights Reserved.

APPLICATION INFORMATION

For safe and effective charging, some strict

requirements have to be satisfied during

charging Li-ion batteries such as high precise

power source for charging (4.2V±50mV), the

accuracy should be higher than 1%. For highly

used capacity, the voltage of the battery should

be charged to the value (4.2V) as possible as

could. Otherwise, the performance and the life

of the battery suffers overcharge. Additionally,

the pre-charge for depleted batteries, charge

voltage, charge current, as well as the

temperature detection and protection, are

required for linear battery chargers. MP2676

provides full protection to guarantee the safety

of the charge system with its perfect four

protection functions: OVP, BOVP, OCP and

OTP.

An internal P-channel MOSFET is integrated to

the MP2676, which can be controlled by the

external control signal from PMIC to achieve

charging function including CC, CV charge

mode and so on. Particularly, connecting

GATDRV to GND can turn on the P-channel

MOSFET while connecting GATDRV to CHRIN

can fully turn off the P-channel MOSFET.

reduces the voltage undershoot or overshoot

during transients. The AC adapter is inserted

live (hot insertion) and sudden step down of the

current in the power MOSFET will cause the

input voltage overshoot.

During an input OVP, the N-channel MOSFET

is turned off in less than 1µs and can lead to

reduces this type of overshoot. However, the

overshoot caused by a hot insertion is not very

dependent on the decoupling capacitance

value. Usually, the input decoupling capacitor is

recommended to use a dielectric ceramic

capacitor with a value between 1µF to 4.7µF.

The output of the MP2676 and the input of the

charge circuit typically share one decoupling

capacitor.

It is strongly recommended that the battery not

be tied directly to the VBAT pin of the device,

as under some failure modes of the IC, the

voltage at the ACIN pin may appear on the

pin to the battery terminal in case the MP2676

fails. The recommended value is between

200kΩ to 1MΩ. With 200kΩ resistance, during

the failure operation, assuming the VBAT pin

voltage is 30V and the battery voltage is 4.2V.

The worst case the current flowing from the

VBAT pin to the charger output is,

(30V − 4.2V)/200kΩ = 130µA,

Such small current can be easily absorbed by

the

bias

current

of

other

components.

case current, but at the same time increases

the error for the 4.35V battery OVP threshold.

As the typical VBAT pin leakage current is

20nA, the error of the battery OVP threshold

the 200kΩ resistor, the worst-case additional

error is 4mV and with a 1MΩ resistor, the worst-

case additional error is 20mV.