SC4539ULTRT Semtech, SC4539ULTRT Datasheet - Page 12

• Manufacturer Part Number: SC4539ULTRT
• Description: TVS
• Manufacturer: Semtech

Specifications of SC4539ULTRT

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Applications Information (continued)
Diode Selection
A Schottky diode with a reverse voltage of 40V and a
forward current rating of 1A should be used with this
device for optimum per formance. The Central
Semiconductor Corporation CMOSH-4E is a suitable diode
for this application.
Selection of Other Components
R
the following equation to select the proper value:
where
Refer to Figure 2 for selecting values for other current set-
tings. Notice that the error increases as the desired I
current decreases.
ISET
V
R
1000
100
sets the maximum load current for the SC4539. Use
ISET
ISET
10
1
Figure 2 – Set Resistor Value Selection Graph
1
= 230×V
= 0.5V (typ).
ISET
/I
LOAD
I
BL
10
(mA)
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 3.
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 3– Layout
SC4539
12