MP2192

– 2A, SYNCHRONOUS STEP-DOWN CONVERTER WITH 25µA IQ

MP2192 Rev. 1.0

MonolithicPower.com

16

5/12/2021

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© 2021 MPS. All Rights Reserved.

APPLICATION INFORMATION

Setting the Output Voltage

The external resistor divider sets the output

voltage (see the Typical Application Circuit on

page 18). Select a feedback resistor (R1) that

reduces the output voltage leakage current. It is

recommended for R1 to be between 100k

Ω and

200kΩ. There is no strict requirement for the

feedback resistor. Select R1 to exceed

10kΩ.

R2 can then be calculated with Equation (2):

OUT

R1

R2

V

1

0.6





(2)

Figure 9 shows the feedback circuit.

R1

R2

VOUT

FB

MP2192

Figure 9: Feedback Network

Table 1 lists recommended resistor values for

common output voltages.

Table1: Resistor Selection for Common Output

Voltages

VOUT (V)

R1 (kΩ)

R2 (kΩ)

1.0

200 (1%)

300 (1%)

1.2

200 (1%)

200 (1%)

1.8

200 (1%)

100 (1%)

2.5

200 (1%)

63.2 (1%)

3.3

200 (1%)

44.2 (1%)

Selecting the Inductor

Most applications work best with a 1µH to

2.2µH inductor. Select an inductor with a DC

resistance below 50

mΩ to optimize efficiency.

A high-frequency switch-mode power supply

with a magnetic device has strong electronic

magnetic inference. Do not use unshielded

power

inductors.

Metal

alloy

inductors

or

multiplayer chip power inductors are ideal

shielded inductors because they can effectively

reduce electromagnetic interference.

For most designs, estimate the inductance

value with Equation (3):

OUT

IN

OUT

1

IN

L

OSC

V

(V

V

)

L

V

I

f





  

(3)

Where

∆IL is the inductor ripple current.

Choose

the

inductor

current

to

be

approximately 30%

of the maximum load

current. The maximum inductor peak current

can be calculated with Equation (4):

L

L(MAX )

LOAD

I

II

2





(4)

MPS inductors are optimized and tested for use

with our complete line of integrated circuits.

Table

2

lists

our

power

inductor

recommendations.

Table 2: Power Inductor Selection

Part Number

Inductance

Value

Manufacturer

MPL-AL4020-1R0

1

μH

MPS

MPL-AL4020-1R2

1.2

μH

MPS

MPL-AL4020-1R5

1.5

μH

MPS

MPL-AL4020-2R2

2.2

μH

MPS

Visit MonolithicPower.com under Products >

Inductors for more information.

Selecting the Input Capacitor

The step-down converter has a discontinuous

input current, and requires a capacitor to supply

AC current to the converter while maintaining

the DC input voltage. Use low-ESR capacitors

for the best performance. Ceramic capacitors

with

X5R

or

X7R

dielectrics

are

highly

recommended due to their low ESR and small

temperature coefficients. For most applications,

a 22µF capacitor is sufficient. Higher output

voltages may require a 44

μF capacitor to

increase system stability.

The input capacitor requires an adequate ripple

current

rating

since

it

absorbs

the

input

switching current. Estimate the RMS current in

the input capacitor with Equation (5):

OUT

OUT

C1

LOAD

IN

IN

VV

I

I

1

VV

















(5)