MP2117

– 1.25MHZ, 2.2A SYNCHRONROUS STEP-DOWN SWITCHER

END OF LIFE, REFER TO MP1605

MP2117 Rev. 0.92

www.MonolithicPower.com

9

6/20/2022

MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.

© 2023 MPS. All Rights Reserved.

APPLICATION INFORMATION

Output Voltage Setting

The external resistor divider sets the output

voltage. It is optional to speed loop response by

adding a small feedforward capacitor CF parallel

with R1. Choose R1*CF time constant around

3usec.

Choose R2 value between 1kΩ and 100kΩ. R1 is

then given by:

OUT

V

R1= R2 (

- 1)

0.6V



Table 1

—Resistor Selection vs. Output

Voltage Setting

VOUT

R1

R2

1.2V

60.4kΩ

60.4kΩ

1.5V

90.9kΩ

60.4kΩ

1.8V

121kΩ

60.4kΩ

2.5V

191kΩ

60.4kΩ)

3.3V

274KΩ

60.4kΩ

Inductor Selection

A 1μH to 10μH inductor with DC current rating at

least 25% higher than the maximum load current

is recommended for most applications. For best

efficiency, the inductor DC resistance should be

<100mΩ. See Table 2 for recommended

inductors and manufacturers. For most designs,

the inductance value can be derived from the

following equation:

(

)

OSC

L

IN

OUT

IN

OUT

f

I

V

V

V

V

L







−



=

Where

ΔIL is inductor ripple current. Choose

inductor ripple current approximately 30% of the

maximum load current, 2.2A.

The maximum inductor peak current is:

L

L(MAX)

LOAD(MAX)

ΔI

I

= I

2

+

Table 2

—Suggested Surface Mount Inductors

Manufacturer

Part Number

Inductance (μH)

Max DCR (mΩ)

Saturation Current (A)

Wurth

7447745012

1.2

17

4.6

Toko

D62LCB-#A918CY-1R0M

1.0

17

3.7

Switcher Input Capacitor CIN1 Selection

The input capacitor reduces the surge current

drawn from the input and switching noise from

the device. The input capacitor impedance at the

switching frequency should be less than input

source impedance to prevent high frequency

switching current passing to the input. Ceramic

capacitors with X5R or X7R dielectrics are highly

recommended because of their low ESR and

small

temperature

coefficients.

For

most

applications, a 10μF~22μF capacitor is sufficient.

Switcher Output Capacitor COUT1 Selection

The output capacitor keeps output voltage ripple

small and ensures regulation loop stable. The

output capacitor impedance should be low at the

switching frequency. Ceramic capacitors with

X5R or X7R dielectrics are recommended. For

most applications, a 22μF~47μF capacitor is

sufficient.

The output ripple ΔVOUT is approximately:

OUT

IN

OUT

OUT

IN

OSC

OSC

OUT

V

(V - V

)

1

ΔV

ESR

V

f

L

8 f

C





 









