MP2623 Rev. 1.0

www.MonolithicPower.com

11

3/16/2012

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Charger Status Indication

MP2623 has two open-drain status outputs:

when the IC supply voltage (VCC) exceeds the

under-voltage

lockout

threshold

and

the

to make sure the regulator can operate normally.

CHGOK indicates charge status. Table 1

describes ACOK and CHGOK outputs under

different charge conditions.

Table 1―Charging Status Indication

ACOK

low

low

In charging

low

high

End of charge, NTC

fault, timer out, thermal

shutdown,

high

high

Timer Operation

MP2623 uses an internal timer to limit the charge

period during both the trickle charge and the total

charge cycle. The MP2623 terminates charging

once the charge time exceeds the time limit. A

good battery should fully recharge within the

allotted time period; otherwise the battery has a

fault. An external capacitor at the TMR pin

programs the time period.

The trickle mode charge time is:





TMR

TRICKLE _ TMR

C

t30 min s

0.1 F

The total charge time is:





TMR

TOTAL _ TMR

C

t

3hours

0.1 F

When time-out occurs, the charger is suspended.

Only refreshing the input power or EN signal can

restart the charge cycle.

Negative Thermal Coefficient (NTC)

Thermistor

The MP2623 has a built-in NTC-resistance

window comparator that allows the MP2623 to

sense the battery temperature through the

thermistor included in the battery pack. Connect

a resistor with an appropriate value from VREF33

to the NTC pin, and connect the thermistor from

the NTC pin to GND. A resistor divider

determines the voltage on the NTC pin as a

function of the battery temperature. Charging

halts when the NTC voltage falls below the lower

NTC window threshold. Charging resumes when

the voltage is within the NTC window range.

Application with Power Selector

MP2623 is a stand-alone, switching charger.

Typically, VIN receives power from the adapter

battery simultaneously so the user can start-up a

device with a drained battery when it is

connected to an adapter. Replace the diode from

the stand-alone switching charger circuit with a

MOSFET to improve system efficiency and

reduce voltage drop of the block device.

An additional MOSFET between VIN and the

battery allows the battery to charge even in the

absence of an adapter or connection to an invalid

adapter. Figure 3 shows a typical application

circuit with power-path management. When the

adapter input is invalid or absent, the block diode

is replaced by a MOSFET controlled by ACOK

signal.