C1608X5R0J106M 데이터 시트보기 (PDF) - ON Semiconductor

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C1608X5R0J106M

3 MHz, 2 A Synchronous Buck Converter

ON Semiconductor 

NCP6323, NCV6323

APPLICATION INFORMATION

Output Filter Design Considerations

The output filter introduces a double pole in the system at

a frequency of

fLC

+

2

@

p

1

@ ǸL

@

C

(eq. 2)

The internal compensation network design of the

NCP/NCV6323 is optimized for the typical output filter

comprised of a 1.0 mH inductor and a 10 mF ceramic output

capacitor, which has a double pole frequency at about

50 kHz. Other possible output filter combinations may have

a double pole around 50 kHz to have optimum operation

with the typical feedback network. Normal selection range

of the inductor is from 0.47 mH to 4.7 mH, and normal

selection range of the output capacitor is from 4.7 mF to

22 mF.

Inductor Selection

The inductance of the inductor is determined by given

peak−to−peak ripple current IL_PP of approximately 20%

to 50% of the maximum output current IOUT_MAX for a

trade−off between transient response and output ripple. The

inductance corresponding to the given current ripple is

ǒVIN * VOUTǓ @ VOUT

L+

VIN @ fSW @ IL_PP

(eq. 3)

The selected inductor must have high enough saturation

current rating to be higher than the maximum peak current

that is

IL_PP

IL_MAX + IOUT_MAX ) 2

(eq. 4)

The inductor also needs to have high enough current

rating based on temperature rise concern. Low DCR is good

for efficiency improvement and temperature rise reduction.

Table 1 shows some recommended inductors for high power

applications and Table 2 shows some recommended

inductors for low power applications.

Table 1. LIST OF RECOMMENDED INDUCTORS FOR HIGH POWER APPLICATIONS

Manufacturer

Part Number

Case Size

(mm)

Rated Current (mA)

L (mH) (Inductance Drop)

MURATA

LQH44PN2R2MP0 4.0 x 4.0 x 1.8 2.2

2500 (−30%)

MURATA

LQH44PN1R0NP0 4.0 x 4.0 x 1.8 1.0

2950 (−30%)

MURATA

LQH32PNR47NNP0 3.0 x 2.5 x 1.7 0.47

3400 (−30%)

Structure

Wire Wound

Wire Wound

Wire Wound

Table 2. LIST OF RECOMMENDED INDUCTORS FOR LOW POWER APPLICATIONS

Manufacturer

Part Number

Case Size

(mm)

Rated Current (mA)

L (mH) (Inductance Drop)

MURATA

LQH44PN2R2MJ0 4.0 x 4.0 x 1.1 2.2

1320 (−30%)

MURATA

LQH44PN1R0NJ0 4.0 x 4.0 x 1.1 1.0

2000 (−30%)

TDK

VLS201612ET−2R2 2.0 x 1.6 x 1.2 2.2

1150 (−30%)

TDK

VLS201612ET−1R0 2.0 x 1.6 x 1.2 1.0

1650 (−30%)

Structure

Wire Wound

Wire Wound

Wire Wound

Wire Wound

Output Capacitor Selection

The output capacitor selection is determined by output

voltage ripple and load transient response requirement. For

a given peak−to−peak ripple current IL_PP in the inductor

of the output filter, the output voltage ripple across the

output capacitor is the sum of three ripple components as

below.

VOUT_PP [ VOUT_PP(C) ) VOUT_PP(ESR) ) VOUT_PP(ESL)

(eq. 5)

where VOUT_PP(C) is a ripple component by an equivalent

total capacitance of the output capacitors, VOUT_PP(ESR)

is a ripple component by an equivalent ESR of the output

capacitors, and VOUT_PP(ESL) is a ripple component by

an equivalent ESL of the output capacitors. In PWM

operation mode, the three ripple components can be

obtained by

IL_PP

VOUT_PP(C) + 8 @ C @ fSW

(eq. 6)

VOUT_PP(ESR) + IL_PP @ ESR

(eq. 7)

VOUT_PP(ESL)

+

ESL

ESL )

L

@

VIN

and the peak−to−peak ripple current is

ǒVIN * VOUTǓ @ VOUT

IL_PP +

VIN @ fSW @ L

(eq. 8)

(eq. 9)

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