Texas Instruments LM3409HV User Manual

1 Introduction
This evaluation board showcases the LM3409HV PFET controller for a buck current regulator. It is
designed to drive 12 LEDs (V
voltage (V = 48V). The switching frequency (f
however f varies across the entire operating range. The circuit can accept an input voltage of 6V-75V.
SWIN
However, if the input voltage drops below the regulated LED string voltage, the converter goes into
dropout and V = V
O
The PCB is made using 4 layers of 2 oz. copper with FR4 dieletric. The evaluation board showcases all
features of the LM3409HV including analog dimming using the IADJ pin and internal PWM dimming using
the EN pin. High frequency external parallel FET shunt PWM dimming can also be evaluated. The board
has a header (J1) with a removable jumper, which is used to select the PWM dimming method.
The evaluation board has a right angle connector (J2) which can mate with an external LED load board
allowing for the LEDs to be mounted close to the driver. This reduces potential ringing when there is no
output capacitor. Alternatively, the LED+ and LED- turrets can be used to connect the LED load.
This board can be easily modified to demonstrate other operating points as shown in
Design Procedure section of the LM3409/3409HV/3409Q/3409QHV PFET Buck Controller for High
Power LED Drivers (SNVS602) data sheet can be used to design for any set of specifications.
Since the board contains a buck regulator designed for 48V input, the efficiency is very high at input
voltages near or less than 48V. The switching frequency increases as input voltage increases, yielding
lower efficiency at higher input voltages. Note that increasing the off-time resistor (R6) will increase the
efficiency at high input voltage.
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SNVA390D – May 2009 – Revised May 2013
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AN-1953 LM3409HV Evaluation Board
= 42V) at a maximum average LED current (I
O
ideally.
IN
100
95
90
85
80
75
40 45 50
INPUT VOLTAGE (V)
Figure 1. Efficiency with 12 Series LEDS AT 1.5A
Copyright © 2009–2013, Texas Instruments Incorporated
SNVA390D – May 2009 – Revised May 2013
= 400 kHz) is targeted for the nominal operating point,
SW
55 60 65 70 75
AN-1953 LM3409HV Evaluation Board
User's Guide
= 1.5A) from a DC input
LED
Section 9. The
1