NCP6354

http://onsemi.com

10

(eq. 1)

normal switching frequency.

Thermal Shutdown

The NCP6354 has a thermal shutdown protection to

protect the device from overheating when the die

temperature exceeds 150

°C. Once the thermal protection is

triggered, the fault state can be ended by re−applying VIN

and/or EN when the temperature drops down below 125

°C.

APPLICATION INFORMATION

Output Filter Design Considerations

The output filter introduces a double pole in the system at

a frequency of

1

2 @ p @ L @ C

(eq. 2)

The internal compensation network design of the

NCP6354 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

trade−off between transient response and output ripple. The

inductance corresponding to the given current ripple is

L +

(eq. 3)

The selected inductor must have high enough saturation

current rating to be higher than the maximum peak current

that is

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)

L (mH)

Rated Current (mA)

(Inductance Drop)

Structure

MURATA

LQH44PN2R2MP0

4.0 x 4.0 x 1.8

2.2

2500 (−30%)

Wire Wound

MURATA

LQH44PN1R0NP0

4.0 x 4.0 x 1.8

1.0

2950 (−30%)

Wire Wound

MURATA

LQH32PNR47NNP0

3.0 x 2.5 x 1.7

0.47

3400 (−30%)

Wire Wound

Table 2. LIST OF RECOMMENDED INDUCTORS FOR LOW POWER APPLICATIONS

Manufacturer

Part Number

Case Size (mm)

L (mH)

Rated Current (mA)

(Inductance Drop)

Structure

MURATA

LQH44PN2R2MJ0

4.0 x 4.0 x 1.1

2.2

1320 (−30%)

Wire Wound

MURATA

LQH44PN1R0NJ0

4.0 x 4.0 x 1.1

1.0

2000 (−30%)

Wire Wound

TDK

VLS201612ET−2R2

2.0 x 1.6 x 1.2

2.2

1150 (−30%)

Wire Wound

TDK

VLS201612ET−1R0

2.0 x 1.6 x 1.2

1.0

1650 (−30%)

Wire Wound

Output Capacitor Selection

The output capacitor selection is determined by output

voltage ripple and load transient response requirement. For

the output filter, the output voltage ripple across the output

capacitor is the sum of three components as below.

(eq. 5)

a ripple component by an equivalent ESR of the output

equivalent ESL of the output capacitors. In PWM operation

mode, the three ripple components can be obtained by