MP2607 – LI-ION CHARGER WITH POWER PATH MANAGEMENT

MP2607 Rev. 1.02

www.MonolithicPower.com

13

6/19/2013

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© 2013 MPS. All Rights Reserved.

APPLICATION INFORMATION

COMPONENT SELECTION

Battery Charging Current

The

charging

current

of

MP2607

is

at ICHSET pin:

)

(

Ω

×

=

CHG

CHG

R

1.260V

1800

I

Where 1.260V is an internal reference voltage

However, due to current limit constraint at the

input source, either adapter or USB port input,

the charging current could be less than above

calculated value if system load demand is high.

MP2607 will always ensure the sum of system

load current and charging current complies with

source current limit, with system load has the

priority. Especially for USB mode, when system

load exceeds the source current limit, charging

is actually stopped and battery is pulled in to

supplement the system load.

When using USB port as input source, if the

charging current is set higher than USB port

current will not be higher than USB current limit

and could be reduced further if system draws

any load.

End of Charge Threshold Current

The end of charge threshold current is set

)

(

R

1.260V

180

I

CHG

EOC

Ω

×

=

Where 1.260V is an internal reference voltage

ICHSET pin.

CV charge mode, MP2607 will terminate charge,

and latch the status pin to indicate the end of

charge.

Trickle Charge Current

When the battery voltage is below the minimum

battery voltage V

characteristics table), the charger operates in a

trickle/preconditioning

mode,

where

the

charging current is typically 7.5% of the

)

(

Ω

×

=

CHG

TRKL

R

1.260V

150

I

Timer for Charge Termination

MP2607 has a built-in timer to terminate the

charge if the timer times out, no matter whether

charged full, the timer is reset. This timer is

at TMR pin, to allow user adjust to different

battery capacity. The timer can be calculated as:

TMR

TMR_F

CHG

C

2 A 1A/36000

1.1hours

2 A I

/36000

1 F

μ+

τ=

×

×

μ+

μ

The timer period is strictly inversely proportional

to the real charging current (either in power

path state or CV charge mode), the sink and

36000

/

Ichg

A

2

+

μ

.

So, the trickle charge timer can be calculated

based on the

/36000

I

A

2

/36000

I

A

2

2

2

TRKL

CHG

17

15

TMR_F

TMR_T

+

μ

+

μ

×

×

τ

=

τ

Due to the power path management function,

the real charging current usually varies during

the whole charging process, thus MP2607

automatically takes into account this variation

and adjust the timer time out accordingly.

Basically

the

timer

increases the

same

proportion as the charging current decreases. If

the charging is stopped due to high system load,

the timer is temporarily suspended. In this way,

the actual energy delivered to the battery, which

is charging current multiplying the charging time,

remains constant.

The time out operation will set the charger into

suspended state and be reported at the status

output pins. To clear the time out status, one

has to recycle the chip enable pin or IN supply.