MP2625B – SINGLE CELL SWITCHING CHARGER WITH POWER PATH CONTROL

MP2625B Rev. 1.01

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25

1/15/2018

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(V)

R2

+

R1

R2

×

V

=

V

IN_LIM

VLIM

(4)

Thus the input voltage is:

(V)

R2

R2

+

R1

×

V

=

V

VLIM

IN_LIM

(5)

1.52V, and a typical value for R2 can be 10kΩ.

With this value, R1 can be determined by:

(V)

V

V

-

V

×

R2

=

R1

VLIM

VLIM

IN_LIM

(6)

For example, for a 4.65V input limit voltage, R2

is 10kΩ, and R1 is 20.6kΩ.

The minimum value and the maximum value of

the input voltage limit can be calculated

according to the accuracy of the resistor and

are used for R1 and R2.

Setting the System Voltage

The system voltage can be regulated to any

value between 4.08V to 4.4V by the resistor

divider on SYSFB pin as R6 and R7 in Figure

10.

SYS

SYS _ REF

R6 R7

VV

R7





(7)

of SYS. With a typical value for R7, 10kΩ, R6

can be determined by:

SYS

SYS _ REF

SYS _ REF

VV

R6 R7

(V)

V





(8)

For example, for a 4.2V system voltage, R7 is

10kΩ, and R6 is 26.5kΩ. 1% resistors are

selected for the R5 and R6.

higher than the maximum value of the auto-

recharge threshold which is 4.05V.

Selecting the Inductor

Inductor selection trades off among cost, size,

and efficiency. A lower inductance value

corresponds to a smaller size, but results in

higher

ripple

currents,

higher

magnetic

hysteretic

losses,

and

higher

output

capacitances. From a practical standpoint, the

inductor ripple current does not exceed 30% of

the maximum load current under worst cases

2A in MP2625B, then,

However, for the light load condition, the

inductor ripple current will be very small which

may cause unstable operation due to the peak

current mode control of the IC. For stable

operation, the experienced minimum limit value

for inductor current ripple is 0.5A. Therefore, the

inductor current ripple is the maximum one of

And the inductance can be calculated according

to Equation (9):

IN

SYS

SYS

L_ MAX

IN

S

VV

V

L

IV

f (MHz)







(

H)

(9)

The peak current of the inductor is calculated

as Equation (10):

)

2

ripple

%

1

(

I

I

)

MAX

(

LOAD

PEAK







(mA)

(10)

voltage, the output voltage, and the switching

frequency, respectively.

Following Table 4 provides the selection guide

of the inductance based on different input

voltage.

Table 4: Inductance Selection Guide under different Input Voltage

SPEC

Inductance Selection

IN

SYS

SYS

LIN

S

VV

V

L

IV

f (MHz)







(uH)

(uH)

L

(uH)

Saturation

Current (A)

(6)

DCR

(mΩ)

Package

5V

0.55

1.25

1.0

>2.8

<50

Application

Required

9V

2.25

2.8

2.2

(5)

>2.8

<50

Application

Required

NOTE:

5)

regular in the application which will have a lower cost.

6)

Saturation Current of the inductor should be higher than the IPEAK, add 0.5A margin here.