MP2633 – 1.5A SINGLE CELL SWITCH MODE BATTERY CHARGER

MP2633 Rev. 1.05

www.MonolithicPower.com

24

4/19/2013

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If charging remains in TC mode beyond the

terminate. The following determines the length of

the trickle-charge period:

TMR

TRICKLE _ TMR

CHG

C( F)

1A

60mins

0.1 F

I

(A)

μ

τ=

×

×

μ

(1)

The maximum total charge time is:

TMR

TOTAL _ TMR

CHG

C( F)

1A

6Hours

0.1 F

I

(A)

μ

τ=

×

×

μ

(2)

Negative Temperature Coefficient (NTC) Input

for Battery Temperature Monitoring

The MP2633 has a built-in NTC resistance

window comparator, which allows the MP2633 to

monitor the battery temperature via the battery-

integrated thermistor. Connect an appropriate

thermistor from the NTC pin to GND. The resistor

divider determines the NTC voltage depending

on the battery temperature. If the NTC voltage

falls outside of the NTC window, the MP2633

stops charging. The charger will then restart if the

temperature goes back into NTC window range.

Input-Current Limiting in Charge Mode

The MP2633 has a dedicated pin that programs

the input-current limit. The current at ILIM is a

fraction of the input current; the voltage at ILIM

indicates the average input current of the

switching regulator as determined by the resistor

value between ILIM and GND. As the input

current approaches the programmed input

current limit, charge current is reduced to allow

priority to system power.

Use the following equation to determine the input

current limit threshold,

ILIM

ILIM

40.5(kΩ)

I=

(A)

R(kΩ)

(3)

Input Over-Current Protection

The

MP2633

features

input

over-current

protection (OCP): when the input current

exceeds 3A, Q2 is controlled linearly to regulate

the current. If the current still exceeds 3A after a

120µs blanking time, Q2 will turn off. A fast off

function turns off Q2 quickly when the input

current exceeds 7A to protect both Q1 and Q2.

Input Voltage Regulation in Charge Mode

In charge mode, if the input power source is not

sufficient to support both the charge current and

system load current, the input voltage will

decrease. As the input voltage approaches the

programmed input voltage regulation value,

charge current is reduced to allow priority of

system power and maintain the input voltage

avoid dropping further.

The input voltage can be regulated by a resistor

divider from VIN pin to REG pin to AGND

according to the following expression:

5

R

5

R

3

R

V

V

REG

R

_

IN

+

×

=

(4)

Where: the VREG is the internal voltage

reference, 1.2V.

Setting the Charge Current

CHG

ISET

70(kΩ)

40(mV)

I(A)=

R(kΩ)RS1(mΩ)

×

(5)

Where: the 40mV is the charge current limit

reference.

Battery Short Protection

The MP2633 has two current limit thresholds. CC

and CV modes have a peak current limit

threshold of 3A, while TC mode has a current

limit threshold of 1.5A. Therefore, the current limit

threshold decreases to 1.5A when the battery

voltage drops below the TC threshold. Moreover,

the switching frequency also decreases when the

BATT voltage drops to 40% of the charge-full

voltage.

Thermal Foldback Function

The MP2633 implements thermal protection to

prevent thermal damage to the IC and the

surrounding components. An internal thermal

sense

and

feedback

loop

automatically

decreases the programmed charge current when

the die temperature reaches 120°C. This function

is called the charge-current-thermal foldback. Not

only does this function protect against thermal

damage, it can also set the charge current based