MP2110 – 3A SYNCHRONOUS BUCK CONVERTER WITH INPUT CURRENT LIMIT

MP2110 Rev. 1.11

www.MonolithicPower.com

12

9/26/2014

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© 2014 MPS. All Rights Reserved.

APPLICATION INFORMATION

Output Voltage Setting

The external resistor divider sets the output

voltage (see Typical Application Circuit on page

1).

Choose R1 around 200kΩ for optimal transient

response. R2 is then given by:

1

V

6

.

0

V

1

R

2

R

=

Table 2—Resistor Selection vs. Output

Voltage Setting

R1

R2

1V

180kΩ (1%)

267kΩ (1%)

1.2V

180kΩ (1%)

180kΩ (1%)

1.8V

180kΩ (1%)

88.7kΩ (1%)

2.5V

340kΩ (1%)

107kΩ (1%)

3.3V

340kΩ (1%)

75kΩ (1%)

3.6V

340kΩ (1%)

68kΩ (1%)

Inductor Selection

A 0.47μH to 4.7μH 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 shall be <200mΩ. See Table 3 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

1

L

×

Δ

×

−

×

=

inductor ripple current approximately 30% of the

maximum load current, 3A.

The maximum inductor peak current is:

2

I

I

I

L

LOAD

)

MAX

(

L

Δ

+

=

Under light load conditions below 100mA, larger

inductance

is

recommended

for

improved

efficiency.

Table 3—Suggested Surface Mount Inductors

Manufacturer

Part Number

Inductance (μH) Max DCR (Ω)

Saturation

Current (A)

Dimensions

LxWxH (mm

Wurth

744777001

1

0.0084

9

7.3X7.3X4.5

Toko

DFE252012C

1

0.059

3

2.5X2.0X1.2

The input capacitor (C1) reduces the surge

current drawn from the input and switching

noise from the device. The input capacitor

impedance at the switching frequency must 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

capacitor is sufficient.

port and with the peak output current, such as

during the TDM frame. That output peak current

is about 3A. Use a large tantalum capacitor to

avoid large voltage drops.

Selecting the Output Capacitor

The output capacitor (C3) is required to

maintain the DC output voltage. Ceramic

capacitors

are

recommended.

Low

ESR

capacitors are preferred to keep the output

voltage ripple low. The output voltage ripple can

be estimated by:

OUT

OUT

OUT

ESR

S1

IN

S

VV

1

V1

R

fL

V

8 f

C3

⎛⎞

⎛⎞

Δ=

× −

×

+

⎜⎟

⎜⎟

×× ×

⎝⎠ ⎝

⎠