CAT4237 datasheet(11/13 Pages) CATALYST

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11 / 13 page

CAT4237

11 of 13

Doc. No. 5013, Rev. A

Characteristics subject to change without notice

BOARD LAYOUT

The CAT4237 is a high-frequency switching

regulator. The traces that carry the high-

frequency switching current have to be

carefully layout on the board in order to

minimize EMI, ripple and noise in general.

The thicker lines on Figure 3 show the

switching current path. All these traces have

to be short and wide enough to minimize the

parasitic

inductance and resistance. The

loop shown on Figure 3 corresponds to the

current path when the CAT4237 internal

switch is closed. On Figure 4 is shown the

current loop, when the CAT4237 switch is

open. Both loop areas should be as small as

possible.

Capacitor C1 has to be placed as close as

possible to the VIN pin and GND. The

capacitor C2 has to be connected separately

to the top LED anode. A ground plane under

the CAT4237 allows for direct connection of

the capacitors to ground. The resistor R1

must be connected directly to the GND pin of

the CAT4237 and not shared with the

switching

current

loops

and

any

other

components.

Figure 3. Closed-switch current loop

closed

Figure 4. Open-switch current loop

open

CAT4237 bảng dữ liệu(PDF) 11 Page - Catalyst Semiconductor