Texas Instruments AN-2255, User Manual, Page: 9 / 26

Primary power supply
(e.g. AC/DC offline converter, DC power supply)
LM3463 EVALUATION
BOARD
W
A
R
N
IN
G:
H
IG
H
D
C
VO
L
T
AG
E
J0
J1
J
1
1
J
1
2
J
1
3
J
1
4
J
1
5
J
1
6
J2
J9 J5 J7
J4 J6 J8
J10
J3
CH0 CH1 CH2 CH3 CH4 CH5 VRAIL
GND
2.5V
VFB
RVFB1
RVFB2
VRAIL
GND
VFB
LM3463 evaluation board
LED strings x 6
Default operation conditions of the board:
I
OUT
per channel: 200 mA
No. of LED per string: 14 (~3.2V forward voltage per LED)
LED turn on voltage: V
RAIL
= 48V
Dimming mode: Direct PWM dimming mode
@ 100% dimming duty
Assumed characteristics of the primary power supply:
VFB = 2.5V
RVFB1 = 39.8 k
RVFB2 = 3.9 k
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Connection Diagram
6 Connection Diagram
Figure 4. Connecting the LM3463 evaluation board to a primary power supply
7 Primary Power Supply
The LM3463 evaluation board is designed to operate with an external primary power supply. A primary
power supply can be any kind of DC power supply with an accessible output voltage feedback node. For
instance, either an AC/DC off-line power converter or a DC/DC switching converter can be used as a
primary power supply. The LM3463 evaluation board should connect to the primary power supply via three
terminals, the VRAIL, GND and VFB as shown in Figure 1.
The board includes three screw type connectors for high current connections, namely J0, J1 and J2. The
J1 and J2 should connect to the positive and GND output terminals of the primary power supply
accordingly with minimum of wire 18 AWG.
Generally, the board is designed to drive from one to six LED strings of 14 serial LEDs per string. The
driving current of each sting is set to 200 mA by default, thus assuming each LED carries a 3.2V forward
voltage, the maximum total output power of this evaluation board under steady state is about 54W.
Because the output voltage of the primary power supply, V
RAIL
is controlled by the Dynamic Headroom
Control (DHC) circuit of the LM3463 to maintain maximum system efficiency, therefore the V
RAIL
must have
a wide and adjustable voltage range.
9 SNVA642 – May 2012 AN-2255 LM3463 Evaluation Board
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