MP2625B – SINGLE CELL SWITCHING CHARGER WITH POWER PATH CONTROL

MP2625B Rev. 1.01

www.MonolithicPower.com

19

1/15/2018

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automatically. ACOK

__________

is an open-drain, active-

low output that indicates the status of input power.

The input is considered valid when the input

voltage is over the UVLO rising threshold, and

280mV higher than the battery voltage to ensure

both the converter and the charger can operate

normally. If the input voltage from an adapter or

from a USB port is indicated OK, ACOK

__________

will turn

low.

During EN

_____

off or thermal shutdown conditions,

the ACOK

__________

turns high to indicate no power is

provided by the input to the system. The ACOK

__________

signal indicates if input supplies power to the

system load or not. Any other condition can not

affect the ACOK

__________

indication as long as the input

power is present.

Charge Status Indication (CHGOK

_____________

)

CHGOK

_____________

is an open-drain, active-low output that

indicates the status of charge. CHGOK

_____________

will be

low during normal charging operation, turn high

after charge full, and blink if a fault condition

happens including NTC fault (battery temperature

invalid) and timer out (bad battery).

In the event of a fault condition, CHGOK

_____________

switches at 6Hz with the 50% duty cycle and

enter “blinking” mode. The user should check the

application circuit to find out the root cause of the

fault condition if the “blinking” signal is asserted.

For no battery condition, CHGOK

_____________

is blinking

according to the transition between charging and

charge full. The blinking frequency is determined

by the cycle of charge and discharge of the

output capacitor.

When the charge current to the battery is low or

in the event the battery is in supplement mode

caused by the insufficient input power, CHGOK

_____________

keeps low to avoid providing false charge full

indication.

Table 2 shows the ACOK

__________

and CHGOK

_____________

status

under different charge conditions.

Table 2: Charger Status Indication

ACOK

CHGOK

Charger Status

low

low

In charging, supplement

mode

low

high

End of charge, ISET

disable charger only.

low

blinking at 6Hz

NTC fault, timer out

high

high

thermal shutdown

Timer Setting

The MP2625B uses an internal timer to terminate

charge if the timer times out. The timer duration

is programmed by an external capacitor at the

TMR pin and related to the real charge current.

The trickle mode charge time is:

TMR

Trickle _ TMR

C

t45

(min)

0.1μF



CHG

(I

1A)



The total charge time is:

TMR

Total_TMR

C

t6.5

(hr)

0.1μF



CHG

(I

1A)



The above equations are based on 1A charge

current. As a result of power path management

control, charge current might vary during normal

operation, under this condition, the MP2625B

automatically takes into account this variation

and adjust the timer period accordingly.

When the charge current is set larger than 1A,

the safe timer period is reduced accordingly with

the same TMR capacitor. If the charge current is

reduced because of insufficient input power, the

timer period is increased proportionally by the

same rate at which the charge current is reduced.

If charge is stopped due to high system load, the

timer is temporarily suspended.

This feature avoids indicating a false trigger

indication for bad battery indication when there is

little charge current delivered to the battery as a

result of the insufficient input power.

When the timer out condition occurs, the

MP2625B terminates the charge at once and

CHGOK

_____________

blinks to indicate the fault status. If one

of the following events happens, the timer is

refreshed and MP2625B re-starts the charge

cycle.