MP2617A, MP2617B

– SINGLE CELL SWITCHING CHARGER WITH POWER PATH

MP2617A, MP2617B Rev. 1.25

www.MonolithicPower.com

21

8/14/2020

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© 2020 MPS. All Rights Reserved.

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

MP2617A and MP2617B 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

MP2617A

and

MP2617B re-starts the charge cycle.



Input re-startup



Refresh EN

_____

/ISET signal



Auto-Recharge

Battery Temperature Monitor

The

MP2617A

and

MP2617B

continuously

monitors battery’s temperature by measuring the

voltage at the NTC pin, typically determined by a

negative

temperature

coefficient

(NTC)

thermistor and external voltage dividers, as

shown in Figure 5. Both the external voltage

divider and the internal reference voltage divider

are pulled up to the same power pin. So actually,

the voltage ratios between the internal and

external dividers are compared. For the NTC

thermistor, the hotter ambient temperature, the

lower resistance is, which corresponds to a lower

voltage ratio, vice versa.

NTC

VCC

Low Temperature

Threshold

VTH_COLD

NTC

Protection

RT2

RT1

RNTC

High Temperature

Threshold

VTH_HOT

Figure 5: NTC Protection Circuit

According to Figure 5， the following equations

are list:

TH_COLD

T2

NTC_LOW

THL

T1

T2

NTC_LOW

TH_HOT

T2

NTC_HIGH

THH

T1

T2

NTC_HIGH

V

R //R

V

=

=

VCC

R +R //R

V

R //R

V

=

=

VCC

R +R //R

VTHL

actually

means

the

low

temperature

threshold limit ratio (Cold Limit) and VTHH means

the high temperature threshold limit ratio (Hot

Limit). RNTC_LOW means the resistance of the

selected NTC thermistor under low temperature,

while RNTC_HIGH means the resistance of the

selected NTC thermistor under high temperature.

Once the external voltage ratio exits the low

temperature threshold (VTHL) to high temperature

threshold (VTHH) range, it means the battery

temperature is out of the COLD to HOT range,

the IC suspends charging and reports the NTC

fault. Charging resumes automatically after the

battery temperature is within the COLD to HOT

temperature range again. Figure 6 shows the

standard control.

Icc

Charge

Voltage

COLD

HOT

Charge

Current

VBATT_REG

Figure 6: Standard NTC Window

Thermal Protection

The

MP2617A

and

MP2617B

implements

thermal protection to prevent the thermal damage

to the IC or surrounding components. An internal

thermal

sense

and

feedback

loop

will

automatically decrease the charge current when

the die-temperature rises to about 120oC. This

function is referred as charge current thermal

fold-back. This feature protects the MP2617A

and MP2617B from excessive temperature due

to high power operation or high ambient thermal