SC441DEVB datasheet(17/21 Pages) SEMTECH

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SC441D

Table 3. Recommended Ceramic Capacitor

Manufacturers

Vendor

Phone

Website

Kemet

408-986-0424

www.kemet.com

Murata

84-237-43

www.murata.com

Taiyo Yuden

408-573-450

www.t-yuden.com

Output Rectifying Diode Selection

Schottky diodes are the ideal choice for SC44D due to

their low forward voltage drop and fast switching speed.

Table 4 shows several different Schottky diodes that work

well with the SC44D. Make sure that the diode has a

voltage rating greater that the possible maximum ouput

voltage. The diode conducts current only when the power

switch is turned off. A diode of 2A will be sufficient for

most designs.

Table 4. Recommended Rectifying Diodes

Part

Vendor

SS23

SS24

Vishay

www.vishay.com

Layout Guidelines

The SC44D contains a boost converter and the place-

ments of the power components outside the SC44D

should follow the layout guidelines of a general boost

converter. The evaluation application circuit on page 8

will be used as an example. C2 and C3 are input decou-

pling capacitor for SC44D VIN pin and main power input.

C2,C3 should be placed as close as possible to the VIN pin

to achieve the best decoupling performance.

To minimize the switching noise, The switching loop

formed by input decoupling capacitors, internal switch,

output Schottky diode and output capacitors must be

minimized. The LED current programming resistor(R6),

compensation network (R9,C5,C7) and soft start capacitor

(C6) should be placed as close as possible to SC44D. The

C4~C7 are decoupling capacitors for LED current source

which prevent IO pins from noise influence. C4~C7

should be placed close to each corresponding IO pin.

Use an isolated local AGND plane underneath the con-

troller and tie it to the negative side of output capacitor

Applications Information (continued)

through R4 for better noise immunity.

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