Datasheet
LM3404, LM3404HV
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SNVS465F –OCTOBER 2006–REVISED MAY 2013
any other circuit path. The continuous current paths on the ground net can be routed on the system ground plane
with less risk of injecting noise into other circuits. The path between the input source and the input capacitor and
the path between the recirculating diode and the LEDs/current sense resistor are examples of continuous current
paths. In contrast, the path between the recirculating diode and the input capacitor carries a large pulsating
current. This path should be routed with a short, thick shape, preferably on the component side of the PCB.
Multiple vias in parallel should be used right at the pad of the input capacitor to connect the component side
shapes to the ground plane. A second pulsating current loop that is often ignored is the gate drive loop formed
by the SW and BOOT pins and capacitor C
B
. To minimize this loop at the EMI it generates, keep C
B
close to the
SW and BOOT pins.
CURRENT SENSING
The CS pin is a high-impedance input, and the loop created by R
SNS
, R
Z
(if used), the CS pin and ground should
be made as small as possible to maximize noise rejection. R
SNS
should therefore be placed as close as possible
to the CS and GND pins of the IC.
REMOTE LED ARRAYS
In some applications the LED or LED array can be far away (several inches or more) from the LM3404/04HV, or
on a separate PCB connected by a wiring harness. When an output capacitor is used and the LED array is large
or separated from the rest of the converter, the output capacitor should be placed close to the LEDs to reduce
the effects of parasitic inductance on the AC impedance of the capacitor. The current sense resistor should
remain on the same PCB, close to the LM3404/04HV.
Table 1. BOM for Design Example 1
ID Part Number Type Size Parameters Qty Vendor
U1 LM3404 LED Driver SOIC-8 42V, 1.2A 1 TI
L1 SLF10145T-470M1R4 Inductor 10 x 10 x 4.5mm 47 µH, 1.4A, 120 mΩ 1 TDK
D1 CMSH2-40 Schottky Diode SMB 40V, 2A 1 Central Semi
Cf VJ0805Y104KXXAT Capacitor 0805 100 nF 10% 1 Vishay
Cb VJ0805Y103KXXAT Capacitor 0805 10 nF 10% 1 Vishay
Cin C3225X7R1H335M Capacitor 1210 3.3 µF, 50V 1 TDK
Co C2012X7R1E105M Capacitor 0805 1.0 µF, 25V 1 TDK
Rsns ERJ8BQFR33V Resistor 1206 0.33Ω 1% 1 Panasonic
Ron CRCW08051333F Resistor 0805 133 kΩ 1% 1 Vishay
Table 2. BOM for Design Example 2
ID Part Number Type Size Parameters Qty Vendor
U1 LM3404HV LED Driver SOIC-8 75V, 1.2A 1 TI
L1 DO5022P-334 Inductor 18.5 x 15.4 x 7.1mm 330 µH, 1.9A, 0.56Ω 1 Coilcraft
D1 CMSH1-60M Schottky Diode SMA 60V, 1A 1 Central Semi
Cf VJ0805Y104KXXAT Capacitor 0805 100 nF 10% 1 Vishay
Cb VJ0805Y103KXXAT Capacitor 0805 10 nF 10% 1 Vishay
Cin C4532X7R2A225M Capacitor 1812 2.2 µF, 100V 1 TDK
Co C3216X7R2A154M Capacitor 1206 0.15 µF, 100V 1 TDK
Rsns ERJ6BQFR43V Resistor 0805 0.43Ω 1% 1 Panasonic
Ron CRCW08051184F Resistor 0805 1.18 MΩ 1% 1 Vishay
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