cat4139 Catalyst Semiconductor, cat4139 Datasheet - Page 10

• Manufacturer Part Number: cat4139
• Description: 22v High Current Boost White Led Driver
• Manufacturer: Catalyst Semiconductor

V
CAT4139
BOARD LAYOUT
The CAT4139 is a high-frequency switching regulator.
The traces that carry the high-frequency switching
current have to be carefully laid out on the board in
order to minimize EMI, ripple and noise in general.
The thicker lines on Figure 4 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 4 corresponds
to the current path when the CAT4139 internal switch
is closed. On Figure 5 is shown the current loop, when
the CAT4139 switch is open. Both loop areas should
be as small as possible.
IN
Doc. No. MD-5032 Rev. A
C
1
Figure 4. Closed-switch Current Loop
SHDN
Figure 6. Recommended PCB Layout
VIN
L
CAT4139
GND
SW
Switch
Closed
FB
D
C
2
V
OUT
R1
10
V
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 CAT4139 allows for direct connection
of the capacitors to ground. The resistor R1 must be
connected directly to the GND pin of the CAT4139 and
not shared with the switching current loops and any
other components.
IN
C
1
Figure 5. Open-switch Current Loop
SHDN
VIN
L
CAT4139
GND
Characteristics subject to change without notice
SW
Switch
Open
© Catalyst Semiconductor, Inc.
FB
D
C
2
V
OUT
R1