sc4541 Semtech Corporation, sc4541 Datasheet - Page 11

• Manufacturer Part Number: sc4541
• Description: High Frequency Led Driver With Integrated Schottky And Simple Interconnect
• Manufacturer: Semtech Corporation

Applications Information ( continued)
The converter has higher efficiency under CCM and the
inductor peak current is calculated by the following
equation.
Assuming CCM, the duty ratio is calculated using the fol-
lowing equation.
V
rectifier.
The inductor ripple current is further shown by the follow-
ing equation.
The recommended inductance shown in Table 1 is based
on operation with regulated 5V input, dual Li-ion or three
Li-ion battery packs. Increased inductance is required for
higher input and output voltage configurations.
Output Capacitor Selection
Ceramic capacitors are placed near IN and OUT pins to
ground in order to minimize ripple voltage. The minimum
capacitance needed for a given ripple can be estimated
using the following equation.
Regulated 5V
Dual Lithium Ion Battery Pack
Three Lithium Ion Battery Pack
D
Table 1 — Inductance Requirements, Driving 6 bWLED
is the forward voltage drop of the internal Schottky
I
C
I
D
V
I
V
V
F
L
L
OUT
S
_
RIPPLE
OUT
IN
_
OUT
RIPPLE
= Switching frequency
PEAK
= Input voltage
= Output current
= Boost output voltage
V
= Peak to peak output voltage ripple
Input Type
OUT
V
V
OUT
V
I
OUT
IN
V
OUT
F
V
IN
S
IN
2
V
F
V
L
D
S
D
V
IN
F
V
IN
S
D
V
D
RIPPLE
L
I
OUT
Input Voltage
8.1 to 12.6V
4.5 to 5.5V
5.4 to 8.4V
Range
L1 Induc-
tance
10µH
22µH
33µH
A 1
quate for most applications. Larger capacitance reduces
voltage ripple, overshoot and undershoot during load
transient as well as improving loop stability margin.
Recommended ceramic capacitor manufacturers are
listed in Table 1.
Kemet
Murata
Taiyo Yuden
µ
F ceramic input and output capacitor should be ade-
Vendor
Table 2
—
Recommended Ceramic Capacitor
Manufacturers
408-986-0424
814-237-1431
408-573-4150
Phone
www.t-yuden.com
www.murata.com
www.kemet.com
Website
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