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Output Capacitor Selection

DVout +

Iout

Cout

1

fs

*

Ip

L

Vout ) Vd * Vin

) Ip

ESR

L = Selected inductor value

ESR = Output capacitor ESR value

Input Capacitor Selection

Rectifier Diode Selection

TPS65140

TPS65145

SLVS497B – SEPTEMBER 2003 – REVISED MARCH 2004

APPLICATION INFORMATION (continued)

Table 1. Inductor Selection

DEVICE

INDUCTOR VALUE

COMPONENT SUPPLIER

DIMENSIONS

ISAT/DCR

4.7 µH

Coilcraft DO1813P-472HC

8.89*6.1*5.0

2.6 A/54 m

Ω

4.2 µH

Sumida CDRH5D28 4R2

5.7*5.7*3

2.2 A/23 m

Ω

4.7 µH

Sumida CDC5D23 4R7

6*6*2.5

1.6 A/48 m

Ω

TPS65140

3.3 µH

Wuerth Elektronik 744042003

4.8*4.8*2.0

1.8 A/65 m

Ω

4.2 µH

Sumida CDRH6D12 4R2

6.5*6.5*1.5

1.8 A/60 m

Ω

3.3 µH

Sumida CDRH6D12 3R3

6.5*6.5*1.5

1.9 A/50 m

Ω

3.3 µH

Sumida CDPH4D19 3R3

5.1*5.1*2.0

1.5 A/26 m

Ω

3.3 µH

Coilcraft DO1606T-332

6.5*5.2*2.0

1.4 A/120 m

Ω

TPS65145

3.3 µH

Sumida CDRH2D18/HP 3R3

3.2*3.2*2.0

1.45 A/69 m

Ω

4.7 µH

Wuerth Elektronik 744010004

5.5*3.5*1.0

1.0 A/260 m

Ω

3.3 µH

Coilcraft LPO6610-332M

6.6*5.5*1.0

1.3 A/160 m

Ω

For best output voltage filtering, a low ESR output capacitor is recommended. Ceramic capacitors have a low

ESR value but depending on the application, tantalum capacitors can be used as well. A 22-µF ceramic output

capacitor works for most of the applications. Higher capacitor values can be used to improve load transient

regulation. See Table 2 for the selection of the output capacitor. The output voltage ripple can be calculated as:

with:

For good input voltage filtering, low ESR ceramic capacitors are recommended. A 22-µF ceramic input capacitor

is sufficient for most of applications. For better input voltage filtering, this value can be increased. See Table 2

and the typical applications for input capacitor recommendations.

Table 2. Input and Output Capacitors Selection

CAPACITOR

VOLTAGE RATING

COMPONENT SUPPLIER

COMMENTS

22 µF/1210

16V

Taiyo Yuden EMK325BY226MM

22 µF/1206

6.3V

Taiyo Yuden JMK316BJ226

To achieve high efficiency, a Schottky diode should be used. The voltage rating should be higher than the

maximum output voltage of the converter. The average forward current should be equal to the average inductor

current of the converter. The main parameter influencing the efficiency of the converter is the forward voltage and

the reverse leakage current of the diode; both should be as low as possible. Possible diodes are: On

Semiconductor MBRM120L, Microsemi UPS120E, and Fairchild Semiconductor MBRS130L.

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