MP2678 Rev. 1.0

www.MonolithicPower.com

8

1/6/2011

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© 2011 MPS. All Rights Reserved.

OPERATION

The MP2678 is a high performance single cell

Li-Ion/Li-Polymer battery charger protection IC.

By integrating the high voltage input protection,

the MP2678 can tolerate an input surge up to

+30V.

The device operates like a linear regulator,

maintaining a 5V output with the input voltage

up to the over voltage protection threshold.

MP2678 features input over voltage protection

(OVP), battery over voltage protection (BOVP)

and over current protection (OCP). When any

fault condition happens, the IC will immediately

turn off the internal N-MOSFET disconnecting

the charging circuit from the input.

For guaranteed safe operation, the MP2678

monitors its own internal temperature and turns

off the N-MOSFET bridging VIN and OUT when

the die temperature exceeds 140ºC.

The device also provides fault indication to the

system when any of the protection events

happens.

Power On Reset

The MP2678 has a power-on reset (POR)

threshold of 2.8V with a built-in hysteresis of

150mV. When the input voltage is below the

POR threshold, the internal N-MOSFET is off.

The IC resets itself and waits for approximately

8ms after the input voltage exceeds the POR

threshold, then, if the input voltage and battery

voltage are safe, the IC begins to turn on the

internal N-MOSFET. The 8ms delay allows any

transient at the input during a hot insertion of

the power supply to settle down before the IC

starts to operate.

Input Voltage Protection

The input voltage is continuously monitored by

internal comparator. When the input voltage

MOSFET will be turn off within 1µs to prevent

the high input voltage from damaging the

electronics in the handheld system. The

hysteresis for the input OVP threshold is given

in the Electrical Specification. When the input

over-voltage condition is removed, the internal

N-MOSFET is turned on again. Because of the

8ms delay before the start, the output is never

enabled if the input rises above the OVP

threshold quickly.

Battery Over-Voltage Protection

The battery voltage OVP threshold is internally

set to 4.35V. The threshold has 150mV built-in

hysteresis. The battery voltage is monitored via

the VB pin and issues an over-voltage signal to

turn off the internal N-MOSFET when the

battery voltage exceeds the battery OVP

threshold. The internal comparator has a built-in

176µs blanking time to prevent any transient

voltage from triggering the OVP. If the OVP

situation still exists after the blanking time, the

power FET is turned off.

Over-Current Protection

The current in the internal N-MOSFET is limited

to prevent charging the battery with an

excessive current. The OCP threshold is preset

impedance and the part restarts again after

8ms delay..

Thermal Protection

The MP2678 monitors its own die temperature

to prevent any thermal failure. When the

internal temperature reaches 140°C,the internal

pulled low. The IC does not resume operation

until the internal temperature drops below

120°C.

EN Function

pin high to turn off the internal N-MOSFET.

N-MOSFET and enter the start-up routine. The

CE

pin has an internal pull down resistor and

can be left unconnected.