CAT4237 Datasheet, PDF (11/13 Pages) Catalyst Semiconductor – High Voltage CMOS Boost White LED Driver

CAT4237
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 28 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 28
corresponds to the current path when the CAT4237 internal
switch is closed. On Figure 29 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
V_IN 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.
Closed
Figure 28. Closed−switch Current Loop
Open
Figure 29. Open−switch Current Loop
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