11

 2005 Semtech Corp.

www.semtech.com

POWER MANAGEMENT

SC190

CIN Selection

The source input current to the SC190 buck converter is

a DC supply current with a triangular ripple riding on it.

To prevent large input voltage ripple a low ESR ceramic

capacitor is required. A minimum value of 4.7µF should

be used for sufficient input voltage filtering and a 10µF

MLCC should be used for optimum input voltage filtering.

Input voltage ripple of approximately 1mV can be achieved

when C

and pre-regulating the input supply to the switching

regulator. (See page 12: Input Voltage Ripple graphs).

COUT Selection

A 10µF ceramic capacitor is recommended for the output

filter capacitor. Output voltage ripple is dominated by the

filter capacitance as shown in the following equation:

Choose an X7R or X5R ceramic dielectric for low ESR and

superior temperature and voltage characteristics. Do not

use Y5V capacitors - their temperature coefficients make

them impractical for this application.

Table 3: Recommended Capacitors

Manufacturer

Part Number

Value

(µF)

Rated Voltage

(VDC)

Type

Case Size

Murata

GRM188R60J475KE19D

4.7

6.3

X5R

0603

Murata

GRM188R60G106ME47D

10

4

X5R

0603

TDK

C1608X5ROG106M

10

4

X5R

0603

Applications Information (Cont.)

)

ESR

(

Cout

)

ripple

(

IL

ripple

_

Vout

•

∆

=