SC194B datasheet(9/17 Pages) SEMTECH

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SC194B

POWER MANAGEMENT

Applications Information (Cont.)

Capacitors with X7R or X5R ceramic dielectric are

strongly recommended for their low ESR and superior

temperature and voltage characteristics. Y5V capacitors

should not be used as their temperature coefﬁcients

make them unsuitable for this application. Table 2 lists

the manufacturers of recommended capacitor options.

Note: Where PSAVE operation is required 22μF must be used for C

OUT.

Table 2 — Recommended Capacitors

Manufacturer/Part No.

Value

(μF)

Rated

Voltage

(VDC)

Temperature

Characteristic

Case Size

Murata

GRM21BR60J226ME39L

6.3

X5R

0805

Murata

GRM188R60J106MKE19

6.3

X5R

0603

TDK

C2012X5R0J106K

6.3

X5R

0603

Final inductor selection will depend on various design

considerations such as efﬁciency, EMI, size and cost.

Table 1 lists the manufacturers of practical inductor

options.

Table 1 — Recommended Inductors

Manufacturer/Part No.

Value

(μH)

DCR

(Ω)

Saturation

Current

(A)

Tolerance

(+%)

Dimensions

LxWxH

(mm)

BI Technologies

HM66304R7

4.7

0.072

1.32

4.7 × 4.7 ×3.0

Coilcraft

D01608C-472ML

4.7

0.09

1.5

6.6 × 4.5 ×3.0

TDK

VLCF4018T- 4R7N1R0-2

4.7

0.101

1.07

4.3 × 4.0 ×1.8

IN Selection

The source input current to a buck converter is non-

continuous. To prevent large input voltage ripple a low

ESR ceramic capacitor is required. A minimum value of

10μF should be used for sufﬁcient input voltage ﬁltering

and a 22μF should be used for improved input voltage

ﬁltering.

OUT Selection

The internal compensation is designed to work with a

certain output ﬁlter corner frequency deﬁned by the

equation:

This single pole ﬁlter is designed to operate with a

minimum output capacitor value of 10μF. Larger output

capacitor values will improve transient performance.

If PSAVE operation is required the minimum capacitor

value is 22μF.

Output voltage ripple is a combination of the voltage

ripple from the inductor current charging and discharging

the output capacitor and the voltage created from the

inductor current ripple through the output capacitor ESR.

Selecting an output capacitor with a low ESR will reduce

the output voltage ripple component, as can be seen in

the following equation:

OUT

COUT

L(ripple)

OUT(ESR)

ESR

COUT

L(ripple)

OUT(ESR)

ESR

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