MP2101 データシートの表示（PDF） - Monolithic Power Systems

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MP2101

1.6MHz Synchronous Step-Down plus 200mA LDO

Monolithic Power Systems 

TM

MP2101 – 1.6MHz SYNCHRONOUS STEP-DOWN PLUS 200mA LDO

APPLICATION INFORMATION

Output Voltage Setting

The external resistor divider sets the output

voltage. The feedback resistor R1 of the switcher

also sets the feedback loop bandwidth with the

internal compensation capacitor (see Figure 1).

R1 of the switcher should be 300kΩ for optimal

transient response. R2 is then given by:

R2 = R1

VOUT1 − 1

0.6V

R4 of the LDO should be 60kΩ for good loop

response. R3 is then given by:

R3 = R4 × ( VOUT2 − 1)

0.6V

Table 1—Resistor Selection vs. Output

Voltage Setting

VOUT

1.2V

1.5V

1.8V

2.5V

R1

300kΩ

(1%)

300kΩ

(1%)

300kΩ

(1%)

300kΩ

(1%)

R2

300kΩ

(1%)

200kΩ

(1%)

150kΩ

(1%)

95.3kΩ

(1%)

R3

60kΩ

(1%)

90kΩ

(1%)

120kΩ

(1%)

190kΩ

(1%)

R4

60kΩ

(1%)

60kΩ

(1%)

60kΩ

(1%)

60kΩ

(1%)

Inductor Selection

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

of at least 25% higher than the maximum load

current is recommended for most applications.

For best efficiency, the inductor DC resistance

should be <200mΩ. See Table 2 for

recommended inductors and manufacturers.

For most designs, the inductance value can be

derived from the following equation:

( ) L = VOUT × VIN − VOUT

VIN × ∆IL × fOSC

Where ∆IL is inductor ripple current.

Choose the inductor ripple current to be

approximately 30% of the maximum load

current (800mA).

The maximum inductor peak current is:

IL(MAX)

= ILOAD

+

∆IL

2

Under light load conditions below 100mA, larger

inductance is recommended for improved

efficiency. Table 3 lists inductors recommended

for this purpose.

Manufacturer

Sumida

Toko

Sumida

Table 2—Suggested Surface Mount Inductors

Part Number

Inductance (µH) Max DCR (Ω)

Saturation

Current (A)

CDRH2D11

2.2

D521C

2.2

CDRH3D16

2.2

0.098

1.27

0.059

1.63

0.072

1.20

Dimensions

LxWxH (mm3)

3.2 x 3.2 x 1.2

5 x 5 x 1.5

4 x 4 x 1.8

Table 3—Inductors for Improved Efficiency at 25mA, 50mA, under 100mA Load.

Manufacturer

Coilcraft

Murata

Sumida

Sumida

Part Number

DO1605T-103MX

LQH4C100K04

CR32-100

CR54-100

Inductance (µH)

10

10

10

10

Max DCR (Ω)

0.3

0.2

0.2

0.1

Saturation

Current (A)

1.0

1.2

1.0

1.2

IRMS (A)

0.9

0.8

0.7

1.4

MP2101 Rev. 1.0

www.MonolithicPower.com

9

8/18/2006

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