MP2618 – 2A, 24V INPUT, 600kHz 2-3CELL SWITCHING LI-ION BATTERY CHARGER

MP2618 Rev. 0.92

www.MonolithicPower.com

12

7/14/2010

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Negative

Thermal

Coefficient

(NTC)

Thermistor

The MP2618 has a built-in NTC resistance

window comparator, which allows MP2618 to

sense the battery temperature via the thermistor

packed internally in the battery pack to ensure a

safe operating environment of the battery. A

resistor with appropriate value should be

connected from VREF33 to NTC pin and the

thermistor is connected from NTC pin to GND.

The voltage on NTC pin is determined by the

resistor divider whose divide ratio depends on

the battery temperature. When the voltage of pin

NTC falls out of NTC window range, MP2618 will

stop the charging. The charger will restart if the

temperature goes back into NTC window range.

Power Path Management

MP2618 can implement a switching charger

circuit with power path management function,

which realizes the current sharing of the charger

and system load. In other words, MP2618 senses

the system current and feeds it back, then

reduces charge current according to the increase

of the system current.

However, after the charge current decrease to 0,

the system current can only be limited by the

adapter.

The system current is satisfied first and always. It

chooses the adapter as its power source when

the adapter plugs in, and the battery is the

backup power source when the adapter is

removed.

Figure 3 to Figure 6 shows the charge profile,

operation waveform and flow chart, respectively.