Datasheet

LT3596
11
3596fa
applicaTions inForMaTion
Inductor Selection
Inductor values between 100µH and 470µH are recom-
mended for most applications. It is important to choose
an inductor that can handle the peak current without
saturating. The inductor DCR (copper wire resistance)
must also be low in order to minimize I
2
R power losses.
Table 1 lists several recommended inductors.
Table 1. Recommended Inductors
PART
L
(µH)
MAX
DCR
(Ω)
CURRENT
RATING
(A) VENDOR
MSS1038
MSS1038
MSS1246T
100
220
470
0.3
0.76
0.935
1.46
0.99
1.0
Coilcraft
www.coilcraft.com
CDRH10D68
CDRH12D58R
100
220
470
0.205
0.362
0.67
1.5
1.0
1.01
Sumida
www.sumida.com
DS1262C2 100
220
0.17
0.35
1.5
1.0
Toko
www.toko.com
VLF10040 100
220
0.22
0.47
1.3
0.9
TDK
www.tdk.com
DR124
DR127
DR74
100
220
470
100
0.26
0.56
0.861
0.383
1.79
1.15
1.6
0.99
Coiltronics
www.cooperet.com
744771220 220 0.40 1.2 Würth Elektronik
www.we-online.com
Capacitor Selection
Low ESR (equivalent series resistance) capacitors should
be used at the outputs to minimize output ripple voltage.
Use only X5R or X7R dielectrics, as these materials retain
their capacitance over wider voltage and temperature
ranges than other dielectrics. Table 2 lists some suggested
manufacturers. Consult the manufacturers for detailed
information on their entire selection of ceramic surface
mount parts.
Table 2. Recommended Ceramic Capacitor Manufacturers
Taiyo Yuden www.t-yuden.com
AVX www.avxcorp.com
Murata www.murata.com
Kemet www.kemet.com
TDK www.tdk.com
Typically 10µF capacitors are sufficient for the V
IN
and BIAS
pins. The output capacitor for the buck regulator depends
on the number of LEDs and switching frequency. Refer to
Table 3 for the proper output capacitor selection.
Table 3. Recommended Output Capacitor Values
(Volts/LED = 3.5V)
SWITCHING
FREQUENCY (kHz) # LEDs C
OUT
(µF)
1000 1 to 3 6.8
>3 4.7
500 1 to 3 10
>3 6.8
200 1 to 3 22
>3 10
Diode Selection
Schottky diodes, with their low forward voltage drop and
fast switching speed, must be used for all LT3596 ap-
plications. Do not use P-N junction diodes. The diode’s
average current rating must exceed the application’s aver-
age current. The diode’s maximum reverse voltage must
exceed the application’s input voltage. Table 4 lists some
recommended Schottky diodes.
Table 4. Recommended Diodes
PART
MAX
CURRENT
(A)
MAX
REVERSE
VOLTAGE
(V) MANUFACTURER
DFLS160 1 60 Diodes, Inc.
www.diodes.com
CMMSH1-60 1 60 Central Semiconductor
www.centralsemi.com
ESIPB 1 100 Vishay
www.vishay.com
Undervoltage Lockout (UVLO)
EN/UVLO programs the UVLO threshold by connecting the
pin to a resistor divider from V
IN
as shown in Figure 2.
Select R1 and R2 according to the following equation:
V V
R
R
IN UVLO( )
. •= +






1 51 1
2
1