MP2617A, MP2617B

– SINGLE CELL SWITCHING CHARGER WITH POWER PATH

MP2617A, MP2617B Rev. 1.25

www.MonolithicPower.com

26

8/14/2020

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© 2020 MPS. All Rights Reserved.

APPLICATION INFORMATION

COMPONENT SELECTION

Setting the Input Current Limit

First the input current limit can be set by the M0

and M1 pins refer to the Table 1, the exact

current value in minimum, typical and maximum

is listed in the EC table.

Under program mode, connect a resistor from

the ILIM pin to AGND to program the input

current limit for different input ports. The

relationship between the input current limit and

setting resistor is as Equation (1) which is

shown in following again:

IN_LIM

ILIM

40000

I

=1.14

(mA)

R

(k

Ω)



(1)

For MP2617A and MP2617B, IILIM is not over 3A.

The tolerance is ±8% of the input current limit

setting.

So for a required minimum input current limit

value, just calculate its typical value first, then

calculate the setting resistor based on Equation

(1). Also the maximum value can be calculated

according to the tolerance.

1% accuracy

resistor is used for this setting. Also, for a given

resistor of RILIM, the input current limit can be

calculated. Following table is an example:

Table 3: Example of RILIM setting

Therefore, if customer selected a 54.9k in 1%

accuracy resistor for the input current limit

setting, then the typical input current limit value

is 830.6mA, the minimum is 756.6mA and the

maximum is 906mA.

Setting the Charge Current

RISET connecting from the ISET pin to AGND

sets the charge current (ICHG). The relationship

between the charge current and setting resistor

is as Equation (2) which is shown in following

again:

CHG

ISET

1800

I

1.15

(mA)

R

(k )





(2)

For example, if the typical ICHG is designed as

2A, then the RISET is calculated at 1.05kΩ. The

tolerance of the ICHG setting is ±10%. If the

minimum

or

maximum

charge

current

is

required, first the typical value should be

calculated according to the tolerance. After that,

calculate the resistor according to formula (2).

1% accuracy resistor is used for this setting.

For a given setting resistor, the charge current

can be calculated by the same way did in the

input current limit setting. Usually in USB mode,

the charge current is always set over the USB

input limit specification. Then the MP2617A and

MP2617B regulates the input current constant

at the limitation value. Thus the real CC charge

current is not the setting value, it varies with

different input and battery voltages.

The maximum

CC

charge

value

can

be

calculated as:

)

A

(

V

I

V

I

TC

ILIM

IN

MAX

_

CC









(3)

Where VTC

is trickle charge threshold (3V) and η

is

the

current

charge

efficiency.

Assume

VIN=5.5V,

IILIM=1A,

suppose

η=83%, thus

ICC_MAX=1.52A.

Figure 7 shows a calculating charge current

curve by limiting the input current limit.

Ilim=

1A

Ilim=0.8

25A

3V

4.2V

Battery Voltage

1A

2A

Ilim=1.44A

Figure 3:ICHG Variation with Different Input

Current Limit

Setting the Input Voltage Limit

The input clamp voltage is set using a resistive

voltage divider from the input voltage to VLIM

pin. The voltage divider divides the input

voltage down to the limit voltage by the ratio:

(V)

R2

+

R1

R2

×

V

=

V

IN_LIM

VLIM

(4)

Resistor

RILIM

(kΩ)

IIN_LIM

(mA)

8%

-8%

Typ.

54.9

830.601

897.049

764.153

Min.

54.351

838.991

906.11

771.872

Max.

55.449

822.377

888.168

756.587