MP26124

–24V INPUT, 2A, 600kHz, 4S SWITCHING LI-ION BATTERY CHARGER

MP26124 Rev. 1.0

www.MonolithicPower.com

13

10/10/2017

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normally. CHGOK indicates the charge status.

Table 1 describes the ACOK and CHGOK

outputs under different charge conditions.

Table 1: Charging Status Indication

ACOK

CHGOK

Charger Status

low

low

In charging

low

high

End of charge, NTC

fault, timer out, thermal

shutdown,

high

high

VCC < UVLO

Timer Operation

The MP26124 uses the internal timer to limit the

charge period during trickle charge and total

charge cycle. Once the charge time exceeds

the time limit, the MP26124 terminates charging.

A good battery should recharge completely

within the allotted time period. Otherwise, the

battery has a fault. An external capacitor at

TMR programs the time period.

The trickle mode charge time can be calculated

with Equation (1):

TMR

TRICKLE _ TMR

C

T

30mins

0.1 F





(1)

The total charge time can be calculated with

Equation (2):

TMR

TOTAL _ TMR

C

T

3hours

0.1 F





(2)

When time-out occurs, charging is suspended.

The charge cycle can be restarted by refreshing

the input power or EN signal or auto-recharge

Negative

Thermal

Coefficient

(NTC)

Thermistor

The MP26124 has a built-in NTC resistance

window comparator that allows the MP26124 to

sense the battery temperature through the

thermistor included in the battery pack. Connect

a resistor with an appropriate value from

VREF33 to NTC, and connect the thermistor

from NTC to GND. A resistor divider determines

the voltage on NTC as a function of the battery

temperature. Charging stops when the NTC

voltage exits the NTC window range. Charging

resumes when the voltage is within the NTC

window range.