MP2617H

– SINGLE-CELL SWITCHING CHARGER WITH NVDC POWER PATH

MP2617H Rev. 1.03

www.MonolithicPower.com

26

1/15/2018

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Table 4: Inductance Selection Guide under different Input Voltage

SPEC

Inductance Selection

IN

SYS

SYS

L

IN

S

V

V

V

L

I

V

f (MHz)







ΔI

ΔI

ΔI

(uH)

(uH)

L

(uH)

Saturation

Current (A)

(6)

DCR

(m

Ω)

Package

5V

0.367

1.25

1.0

>3.95

<50

Application

Required

9V

1.5

2.8

2.2

>3.95

<50

Application

Required

12V

1.75

3.5

2.2

>6

(7)

<50

Application

Required

For the condition that VIN is higher or equal to

12V, and the total output power including

system load and battery charging is over 10W,

an 1A schottky diode from SW to GND is

required. The voltage rating of the schottky

diode is usually selected at 30V.

Selecting the Input Capacitor

application circuit absorbs the maximum ripple

current from the PWM converter, which is given

by Equation (15):

SYS _ MIN

IN _ MAX

SYS _ MIN

RMS _ MAX

CC _ MAX

IN _ MAX

V

(V

V

)

II

V





(15)

the maximum ripple current is 1.3A. Select the

input capacitors so that the temperature rise

caused by the ripple current does not exceed

10°C. Ceramic capacitors with X5R or X7R

dielectrics are recommended because of their

low ESR and small temperature coefficients.

For most applications, use a 10µF capacitor.

When input voltage is over 10V, 22uF capacitor

Besides, usually a small cap with at least 1uF

(C1) from IN to GND is required to be put as

much close as possible to the IC.

For the input voltage is high to 14V, consider

the spike when input insert, select the input

capacitors (both the 22uF and 1uF) in 25V

rating.

Selecting the Output Capacitor

application circuit is parallel with the SYS load.

ripple current and smoothes the output voltage.

Its impedance must be much less than that of

the system load to ensure that it absorbs the

ripple current properly.

Ceramic capacitors are recommended for their

lower ESR and smaller size, which allows the

ESR of the output capacitor to be ignored. The

output voltage ripple can be calculated with

Equation (16):

%

L

f

2

C

8

V

V

1

V

V

r

2

S

IN

SYS

SYS

SYS

















(16)

To guarantee ±0.5% system voltage accuracy,

the maximum output voltage ripple must not

exceed 0.5% (e.g.: 0.1%). The maximum output

voltage ripple occurs at the minimum system

voltage and the maximum input voltage.

The output capacitor can be calculated with

Equation (17):

SYS _ MIN

IN

SYS

2

S

V

1

V

C

8 f

L

r







  

(17)

When SYSFB pin is floating, output voltage

ripple is the main concern to select the output

selection guide about the SYS capacitance

selection under typical inputs.

NOTE:

6)

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

7)

This requirement is for SYS short protection consideration. It could be >3.95A as usual if this feature is not included in the

application.