sc4540 Semtech Corporation, sc4540 Datasheet - Page 12

• Manufacturer Part Number: sc4540
• Description: High Ei Ciency Boost Converter For Up To 10 Leds
• Manufacturer: Semtech Corporation

Applications Information (continued)
Diode Selection
A Schottky diode with a reverse voltage of 60V and a
forward current rating of 1A should be used with this
device for optimum performance. The ST Microelectronics
STPS05602 is a recommended diode for this application.
Selection of Other Components
R
the following equation to select the proper value:
where
Refer to Figure 1 for selecting values for other current set-
tings. Note that the error increases as the desired I
current decreases.
ISET
100
10
V
R
1
sets the maximum load current for the SC4540. Use
ISET
ISET
1
Figure 1 – Set Resistor Value Selection Graph
= 230×V
= 0.5V (typ).
ISET
/I
LOAD
R
IS E T
10
(k
Ω
)
T o le ra n ce
C u rre n t
T yp ica l
R
IS E T
100
BL
PCB Layout Considerations
Poor layout can degrade the performance of the DC-DC
converter and can be a contributory factor in EMI prob-
lems, ground bounce, thermal issues, and resistive voltage
losses. Poor regulation and instability can result. A typical
layout is shown in Figure 4.
The following design rules are recommended:
•
•
•
Place the inductor and fi lter capacitors as close
to the device as possible and use short, wide
traces between the power components.
Route the output voltage feedback path away
from the inductor and LX node to minimize
noise and magnetic interference.
Use a ground plane to further reduce noise
interference on sensitive circuit nodes.
Figure 4– Layout
SC4540
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