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C535676
Connector
P6
P1
Anode of
First LED
Cathode of
Last LED
User's Guide
SNVA193E–January 2007–Revised April 2013
AN-1545 LM3404/LM3404HV Evaluation Board
1 Introduction
The LM3404/04HV is a buck regulator derived controlled current source designed to drive a series string
of high power, high brightness LEDs (HBLEDs) such as the Luxeon™ K2 Emitter at forward currents of up
to 1.0A. The board can accept an input voltage ranging from 6V to 42V when using the LM3404. When
using the pin-for-pin compatible LM3404HV the upper bound of input voltage is 75V. The converter output
voltage adjusts as needed to maintain a constant current through the LED array. The LM3404/04HV is a
true step-down regulator with an output voltage range extending from a V
O(MIN)
of 200 mV (the reference
voltage) to a V
O(MAX)
determined by the minimum off time (typically 300 ns). It can maintain regulated
current through any number of LEDs as long as the combined forward voltage of the array does not
exceed V
O(MAX).
.
2 Circuit Performance LM3404
The LM3404 circuit and BOM have been designed to provide a constant forward current of 1.0A to a
single LED with a forward voltage of approximately 3.7V (Typical of white, blue, and green LEDs using
InGaN technology) from an input of 24V ±10%. Over the input voltage range of 6V to 42V the average
LED current, I
F
, is 1.0A ±10%, the ripple current, Δi
F
, will not exceed 400 mA
P-P
, and the switching
frequency is 450 kHz ± 10%.
3 Circuit Performance LM3404HV
The LM3404HV circuit and BOM have been designed to provide a constant forward current of 1.0A to a
single LED with a forward voltage of approximately 3.7V from an input of 48V ±10%. Over the input
voltage range of 6V to 75V the average LED current, I
F
, is 1.0A ±10%, the ripple current, Δi
F
, will not
exceed 400 mA
P-P
, and the switching frequency is 200 kHz ± 10%.
4 Connecting to LED Array
The LM3404/04HV Evaluation Board includes a female 6-pin SIP, J1, connector as well as two standard
94mil turret connectors for the cathode and anode connections of the LED array. Figure 1 shows the
pinout of J1. Solid 18 or 20 gauge wire with about 1 cm of insulation stripped away makes a convenient,
solderless connection to J1.
Figure 1. Connecting to LED Array
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1
SNVA193E–January 2007–Revised April 2013 AN-1545 LM3404/LM3404HV Evaluation Board
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