MP2605 datasheet(9/13 Pages) MPS

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MP2605 – 28V, 1A LINEAR BATTERY CHARGER WITH TRICKLE CHARGE AND TIMER

MP2605 Rev. 0.94

www.MonolithicPower.com

1/25/2010

MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.

OPERATION

Input Voltage Range

The MP2605 has built-in input voltage surge

protection as high as +28V. The charger IC will

be automatically disabled when the input

voltage is lower than 3.0V or higher than 7.0V.

The open-drain pin ACOK is used to indicate

input

power

good

condition

(i.e.

3.0V<VIN<7.0V). If the input voltage is lower

than the battery voltage, the IC is also disabled

to prevent the battery from draining.

Charge Cycle (Mode Change: Trickle -> CC->

CV)

Figure 2 shows the typical charging profile for

the MP2605. For a fully depleted battery with a

terminal voltage lower than 2.6V, the MP2605

will start with the trickle charge (preconditioning)

at 10% of the full charge current based on the

value of RCHG. If the charger stays in trickle

mode longer than 32768 cycles, the battery

fault condition will be indicated by flashing the

CHG

LED. After the battery voltage reaches

2.6V, the charger begins charging using the

programmed charge current (ICHG).This is

referred to as Constant Current (CC) mode.

Once the battery voltage reaches 4.2V, the

charger will operate in the constant voltage (CV)

mode until the battery is fully charged. The

charge current drops during CV mode, and the

battery full indication is set when the charge

current is reduced to 20% of the programmed

constant current value (ICHG). The charge

process is then terminated. Recharge will start

after the battery voltage is reduced to 4.0V.

After 262144 cycles of continuous charging, if

the battery still has not reached 20% of the ICHG

condition, the on-chip timer will terminate the

charger to prevent charging the dead battery

excessively and the fault condition will be

flagged by flashing the CHG LED.

Charge Termination

The charge current will gradually decrease in

CV mode as the battery approaches full. The

battery full threshold is internally programmed

to be 20% of the ICHG. When the charge current

reaches this threshold, the charger IC will be

automatically turned off.

2.6V

4.2V

VBATT

10% of ICHG

20% of ICHG

Trickle

Charging

Complete

Charging

ICHG

IBATT

Figure 2—MP2605 Typical Charging Profile

Automatic Recharge

When VBATT drops to 4.0V, the charger will

automatically restart the charge cycle until the

20% ICHG condition is met again. When the input

adapter is unplugged, or the charger is disabled

and/or terminated, the leakage current from the

battery to the MP2605 is less than 1uA.

Programming of Charge Current and Battery

Full Current

The charge current (ICHG) is set by a resistor

(RCHG) connected from the ISET pin to GND,

)

(

1700

)

(

CHG

Ω

The relationship between the charge current

and the programming resistance is established

by the following table and graph.

Table 1—RCHG and ICHG Relationship

RCHG (kΩ)

ICHG (mA)

1.65

1000

1.82

900

2.05

800

2.32

700

2.74

600

3.3

500

4.12

400

5.6

300

8.45

200

100

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