MP2617A, MP2617B

– SINGLE CELL SWITCHING CHARGER WITH POWER PATH

MP2617A, MP2617B Rev. 1.25

www.MonolithicPower.com

20

8/14/2020

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system load will be powered by the battery

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

310mV 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

VIN absent,

EN disable,

thermal shutdown

Timer Setting

The MP2617A and MP2617B 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

battery current (IBATT).

(s)

10

1

40000

I

2

0.73

C

t

6

-

BATT

TMR

Cycle











The trickle mode charge time is:

(s)

t

45055

t

Cycle

R

Trickle_TM





If a CTMR (0.1µF) is connected, the trickle charge

current is just 0.1A, and suppose the capacitance

and battery current is fixed at this value, the

trickle charge time is calculated about 31 minutes.

The total charge time (during CC and CV mode)

is:

(s)

t

3407871

t

Cycle

Total_TMR





If a CTMR (0.1µF) is connected, the CC charge

current is 1A, and suppose the capacitance and

battery current is fixed at this value, the CC

charge time is calculated about 5.3 hours.

During CV mode, as the charge current decrease

naturally, so the timer cycle increases naturally

according to the formula. The time period also

will increased during CV mode. The battery is

closer to full state, the time period is longer.

As a result of power path management control,

charge

current

might

vary

during

normal

operation, under this condition, the MP2617A

and MP2617B automatically takes into account

this

variation

and

adjust

the

timer

period

accordingly.