Datasheet

LT3760
12
3760fc
Table 1. Inductor Manufacturers
MANUFACTURER PHONE NUMBER WEB
Sumida 408-321-9660 www.sumida.com
Würth Elektronik 605-886-4385 www.we-online.com
Vishay 402-563-6866 www.vishay.com
Coilcraft 847-639-6400 www.coilcraft.com
Coiltronics 561-998-4100 www.cooperet.com
Input Capacitor
The input capacitor of the LT3760 boost converter will sup-
ply the transient input current of the power inductor. Values
between 2.2µF and 10µF will work well for the LT3760. Use
only X5R or X7R ceramic capacitors to minimize variation
over voltage and temperature. If inductor input voltage is
required to operate near the minimum allowed operational
V
IN
for the I.C., a larger capacitor value may be required.
This is to prevent excessive input voltage ripple causing
dips below the minimum operating input voltage.
Output Capacitor
Low ESR ceramic capacitors should be used at the LT3760
converter output 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. The output capacitance requirements
for several LED driver application circuits are shown in
the Applications Information section for various I
LED
,
V
IN
, V
OUT
, L and f
OSC
values. Some suggested capacitor
manufacturers are listed in Table 2.
Table 2. Ceramic Capacitor Manufacturers
MANUFACTURER PHONE NUMBER WEB
TDK 516-535-2600 www.tdk.com
Kemet 408-986-0424 www.kemet.com
Murata 814-237-1431 www.murata.com
Taiyo Yuden 408-573-4150 t-yuden.com
AVX 843-448-9411 www.avxcorp.com
applicaTions inForMaTion
Schottky Rectifier
The external diode for the LT3760 boost converter must
be a Schottky diode, with low forward voltage drop
and fast switching speed. Table 3 lists several Schottky
manufacturers. The diodes average current rating must
exceed the application’s average output current. The
diode’s maximum reverse voltage must exceed the
maximum output voltage of the application. For PWM
dimming applications be aware of the reverse leakage of
the Schottky diode. Lower leakage current will drain the
output capacitor less during PWM low periods, allowing
for higher PWM dimming ratios. The companies below
offer Schottky diodes with high voltage and current ratings.
Table 3. Schottky Rectifier Manufacturers
MANUFACTURER PHONE NUMBER WEB
Diodes, Inc. 805-446-4800 www.microsemi.com
On Semiconductor 888-743-7826 www.onsemi.com
Zetex 631-360-2222 www.zetex.com
Vishay Siliconix 402-563-6866 www.vishay.com
Power MOSFET Selection
Several MOSFET vendors are listed in Table 4. Consult the
factory applications department for other recommended
MOSFETs. The power MOSFET selected should have a
V
DS
rating which exceeds the maximum Overvoltage
Protection (OVP) level programmed for the application.
(See “Programming OVP level” in the Applications
Information section). The MOSFET should also have a
low enough total gate charge Q
g
(at 7V V
GS
) and a low
enough switching frequency (f
OSC
) to not exceed the
INTV
CC
regulator current limit, where loading on INTV
CC
pin due to gate switching should obey,
I
GATE
= Q
g
• f
OSC
≤ 40mA