Texas Instruments LM3409 Demonstration Board LM3409EVAL/NOPB LM3409EVAL/NOPB 用户手册
产品代码
LM3409EVAL/NOPB
INPUT VOLTAGE (V)
EF
F
IC
IEN
C
Y
(%
)
100
95
90
85
80
75
15
20
25
30
35
40
45
User's Guide
SNVA391D – May 2009 – Revised May 2013
AN-1954 LM3409 Demonstration Board
1
Introduction
This demonstration board showcases the LM3409 PFET controller for a buck current regulator. It is
designed to drive 4 LEDs (V
designed to drive 4 LEDs (V
O
= 15V) at a maximum average LED current (I
LED
= 1A) from a DC input
voltage (V
IN
= 24V). The switching frequency (f
SW
= 525 kHz) is targeted for the nominal operating point,
however f
SW
varies across the entire operating range. The circuit can accept an input voltage of 6V-42V.
However, if the input voltage drops below the regulated LED string voltage, the converter goes into
dropout and V
dropout and V
O
= V
IN
ideally.
The PCB is made using 2 layers of 2 oz. copper with FR4 dielectric. The board showcases several
features of the LM3409 including both analog dimming using a potentiometer (R5) tied to the IADJ pin and
internal PWM dimming using the EN pin. There is a header (J1) with a removable jumper, which is used to
select PWM dimming or low power shutdown.
features of the LM3409 including both analog dimming using a potentiometer (R5) tied to the IADJ pin and
internal PWM dimming using the EN pin. There is a header (J1) with a removable jumper, which is used to
select PWM dimming or low power shutdown.
The 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.
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
. The
LM3409 / LM3409HV / LM3409Q / LM3409QHV / LM3409N PFET Buck Controller for High Power LED
Drivers (
Drivers (
) data sheet's Design Procedure can be used to design for any set of specifications.
Figure 1. Efficiency with 4 Series LEDS AT 1A
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1
SNVA391D – May 2009 – Revised May 2013
AN-1954 LM3409 Demonstration Board
Copyright © 2009–2013, Texas Instruments Incorporated