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

MP2676 Rev. 0.91

www.MonolithicPower.com

8

12/7/2010

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OPERATION

The MP2676 is a highly integrated circuit

designed to provide complete Li-ion battery

charger protection against input over voltage,

input over current and battery over voltage. The

IC continuously monitors the input voltage, the

input current and the battery voltage, when any

of the monitored parameters exceeds its

threshold, the IC immediately turns off the

internal N-channel MOSFET to remove the

power from the charge system before any

damage occurs. Moreover, all protections also

have blanking times against false triggering due

to voltage spikes or current transients. The IC

also features thermal shutdown protection, if

the temperature exceeds 140ºC, MP2676 will

turn off the internal MOSFET bridging ACIN and

CHRIN.

MP2676 integrates a P-channel MOSFET with

the body diode reverse protection to replace the

external P-channel MOSFET and block diode

for charge function of portable devices with

PMIC (Power Management IC).

Power Up

The MP2676 has a power-on reset (POR)

threshold of 2.65V with a built-in hysteresis of

130mV. When the input voltage is below the

POR

threshold,

the

internal

N-channel

MOSFET is off. The IC resets itself and waits

for about 10ms after the input voltage exceeds

the POR threshold, then, if the input voltage

and battery voltage are safe, the IC begins to

soft-start the internal N-channel MOSFET. The

10ms delay allows any transient at the input

during a hot insertion of the power supply to

settle down before the IC starts to operate. The

soft-start slowly turns on the N-channel

MOSFET to reduce the inrush current as well

as the input voltage drop during the transition.

Input Over-voltage Protection (OVP)

The input voltage is continuously monitored by

the internal comparator CP1 in the block

diagram (Figure 1), the OVP threshold is set by

an internal resistive divider and an accurate

reference generated by the IC itself. The

protection threshold is set to 6V. When the

input voltage exceeds the threshold, the CP1

outputs a logic signal to turn off the N-channel

MOSFET within 1µs to prevent the high input

voltage from damaging the electronics in the

handheld system. The hysteresis of the input

OVP threshold is given in the Electrical

Characteristic. When the input over-voltage

condition is removed, the N-channel MOSFET

is turned on again by running through the soft-

start. Because of the 10ms delay before the

soft-start, the output is never enabled if the

input rises above the OVP threshold within

10ms.

Battery Over-voltage Protection (BOVP)

The battery voltage OVP threshold is internally

set to 4.35V, and the threshold has 240mV

built-in hysteresis. When the battery voltage

exceeds the battery OVP threshold, the internal

comparator CP2 has a built-in 200µs blanking

time to prevent any transient voltages from

triggering the BOVP. If the BOVP situation still

exists after the blanking time, the N-channel

MOSFET is turned off. There is an internal 4-bit

binary counter monitoring the occurrences of

the BOVP event. If the BOVP event occurs 16

times, the N-channel MOSFET is turned off

permanently. Recycling the input power will

reset the counter and restart the MP2676.

Over-current Protection (OCP)

The current through the N-channel MOSFET is

limited to prevent charging the battery with an

excessive current. The current limit threshold is

preset to 1.6A. The OCP comparator CP3 has a

built-in 180µs delay to prevent false triggering

by transient signals. When OCP happened,

VOUT shuts down and takes 60ms delay to soft

start as the OCP condition is removed. The

OCP function also has a 4-bit binary counter

that accumulates the occurrences of OCP

event. When the total count reaches 16, the N-

channel MOSFET is turned off permanently

unless the input power is recycled.

Thermal Protection

The MP2676 monitors its own die temperature

to prevent thermal failures. When the internal

temperature reaches 140°C, the internal N-

channel MOSFET is turned off. The IC does not

resume operation until the internal temperature

drops below 120°C