SC5010 View Datasheet(PDF) - Semtech Corporation
Part Name
Description
MFG CO.
SC5010
Semtech Corporation
'SC5010' PDF : 36 Pages View PDF
SC5010
Components Selection (continued)
160mA, and 1x 10μF or 2x 4.7μF capacitors are
recommended.
During load transient, the output capacitor supplies or
absorbs additional current before the inductor current
reaches its steady state value. Larger capacitance helps
with the overshoot/undershoots during load transient
and loop stability. Recommended ceramic capacitor
manufacturers are listed in Table 4.
to drive LED loads. This boost switching structure has an
advantage in that the SC5010 is not exposed to high
voltage. Only the external power MOSFET, freewheeling
diode and the inductor will be exposed to the output
voltage. The external power MOSFET should be selected
with its voltage rating higher than the output voltage by
minimum 30%. The current rating should be enough to
handle the inductor peak current. Low R (on) MOSFETs
DS
are preferred for achieving better efficiency.
Table 4 — Recommended Ceramic Capacitor Vendors
Vendor
Kemet
Vishay
TDK
Murata
Taiyo Yuden
Web site
www.kemet.com
www.vishay.com
www.tdk.com
www.murata.com
www.t-yuden.com
Input Capacitor Selection
X5R or X7R ceramic capacitor is recommended for input
bypass capacitor. A 1μF capacitor is sufficient for the VCC
input. Bypass the VIN input with a 4.7μF or larger ceramic
capacitor.
Output Freewheeling Diode Selection
Schottky diodes are the ideal choice for SC5010 due to
their low forward voltage drop and fast switching speed.
Table 5 shows several different Schottky diodes that work
properly with the SC5010. Verify that the diode has a
voltage rating greater than the maximum possible output
voltage. The diode conducts current only when the power
switch is turned off. The diode must be rated to handle the
average output current. A diode rated for 1A average
current will be sufficient for most designs.
Table 5 — Recommended Rectifier Diodes
Rectifier Diode
DFLS140
1N5819HW
SS13/14/15/16, SS23/24/25/26
Vendor Web site
www.diodes.com
www.diodes.com
www.vishay.com
External Power MOSFET Selection
The boost converter in SC5010 uses an external power
MOSFET to regulate the output voltage and output power
The GD (gate driver) on SC5010 provides 1A (peak) current
driving capability which is suitable for most MOSFETs for
high frequency operation. The average current required to
drive the MOSFET is given by the following equation.
IGATE = QG x fSW
QG — Gate charge
The R and its RMS current I of the power MOSFET
DS(ON)
S_RMS
will generate the conduction loss using the following
equation.
PCOND
=
I2
S_RMS
x
RDS(on)
The MOSFET’s switch loss can be calculated using the fol-
lowing equation.
PSW = ½ x VIN x IL_PEAK x fSW x (TON + TOFF)
Where TON and TOFF are the MOSFET’s on and off time
and they can be estimated by the following
equations.
4
7W
JG
21 U 9
5
SODWH D X
J
4
7
W
JG
2 ))
I 9 SODWH D X
5
J
Where t , t , Q and V can usually be found from data-
r f gd
plateau
sheet of the selected MOSFET. R is the resistance of the
g
optional resistor connected in series on the gate of the
MOSFET.
25
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