Texas Instruments AN-2255 User manual

AN-2255 LM3463 Evaluation Board
User's Guide
Literature Number: SNVA642
May 2012

Contents
1 Introduction ........................................................................................................................ 5
2 Standard Settings of the LM3463 Evaluation Board ................................................................. 5
3 LM3463 Evaluation Board Schematic ..................................................................................... 6
4 Bill Of Materials .................................................................................................................. 6
5 Board Layout ...................................................................................................................... 8
6 Connection Diagram ............................................................................................................ 9
7 Primary Power Supply ......................................................................................................... 9
8 Response of the DHC Loop ................................................................................................ 12
9 Reducing the System Startup Time ...................................................................................... 12
10 MOSFET Power Dissipation Limit ........................................................................................ 13
11 Analog Dimming Control .................................................................................................... 13
12 PWM Dimming Control ....................................................................................................... 13
13 Disabling Output Channel(s) ............................................................................................... 17
14 Cascading the LM3463 evaluation board .............................................................................. 17
15 PCB Design ...................................................................................................................... 18
16 Typical Waveforms ............................................................................................................ 20
2Table of Contents SNVA642–May 2012
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List of Figures
1 Circuit diagram of the LM3463 evaluation board ....................................................................... 6
2 Top Layer .................................................................................................................... 8
3 Bottom Layer ................................................................................................................ 8
4 Connecting the LM3463 evaluation board to a primary power supply............................................... 9
5 Different voltage levels of the VRAIL at system startup................................................................. 10
6 Procedures of setting the rail voltage levels. .......................................................................... 11
7 Procedure of selecting a primary power supply ....................................................................... 12
8 Adjusting the tST with different value of RISR......................................................................... 13
9 Typical waveforms of a complete data frame in the serial interface mode ........................................ 15
10 PWM dimming duty vs code value of a data byte..................................................................... 15
11 Conversion characteristic of the analog voltage to PWM dimming control circuit ................................ 17
12 A 12 channel lighting system using serial interface mode for dimming control ................................... 18
13 A 12 channel lighting system using DC interface mode for dimming control...................................... 19
14 A 12 channel lighting system using Direct PWM mode for dimming control ...................................... 19
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User's Guide
SNVA642–May 2012
AN-2255 LM3463 Evaluation Board
The LM3463 is a 6-channel linear LED driver with Dynamic Headroom Control (DHC) designed to drive six
strings of high brightness LEDs at maximum supply voltage up to 95V. Each output channel of the
LM3463 evaluation board is designed to deliver 200 mA of LED driving current. The LED turn on voltage
is set to 48V by default, thus the board is able to deliver up to 57.6W total output power. The six output
channels are divided into 4 individual groups to facilitate average LED current control by means of PWM
dimming. The PWM dimming control interface of the LM3463 can accept standard TTL level PWM signals,
analog voltage or serial data to control the dimming duty of the four LED groups individually. The analog
dimming control interface accepts an analog control voltage in the range from 0V to 2.5V to adjust the
reference voltage of the linear current regulators, which enables true LED current adjustment. This
evaluation board is designed to be connected to an external primary power supply. Using three connection
wires, the VIN, GND and VFB, the dynamic Headroom Control (DHC) circuit of the LM3463 adjusts the
output voltage of the primary power supply to maximize system efficiency.
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www.ti.com Introduction
1 Introduction
The LM3463 is a 6-channel linear LED driver with Dynamic Headroom Control (DHC) designed to drive six
strings of high brightness LEDs at maximum supply voltage up to 95V. Each output channel of the
LM3463 evaluation board is designed to deliver 200 mA of LED driving current. The LED turn on voltage
is set to 48V by default, thus the board is able to deliver up to 57.6W total output power. The six output
channels are divided into 4 individual groups to facilitate average LED current control by means of PWM
dimming. The PWM dimming control interface of the LM3463 can accept standard TTL level PWM signals,
analog voltage or serial data to control the dimming duty of the four LED groups individually. The analog
dimming control interface accepts an analog control voltage in the range from 0V to 2.5V to adjust the
reference voltage of the linear current regulators, which enables true LED current adjustment. This
evaluation board is designed to be connected to an external primary power supply. Using three connection
wires, the VIN, GND and VFB, the dynamic Headroom Control (DHC) circuit of the LM3463 adjusts the
output voltage of the primary power supply to maximize system efficiency.
2 Standard Settings of the LM3463 Evaluation Board
• Input voltage range: 12V to 95V
• LED turn on voltage: 48V
• Nominal forward voltage of a LED string: 42V
• Output current per ch.: 200 mA
• System clock freq.: 246 kHz
• DHC cut-off freq.: 0.1Hz
• Mode of dimming control: Direct PWM Mode
5
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GD0
OutP
REFRTN
VIN
SE0
U1
LM3463
VREF
IOUTADJ
FCAP
CDHC
ISR
VCC
VLedFB
GND
Faultb
MODE
DIM01
DIM23
DIM4
DIM5
EN
DRVLIM
0
REFRTN
R10
NC
R11
0.47 µF
25V
C6
22 nF
25V
C5
1 µF
16V
C4
NC
R9
NC
R7
0
R37
GND
GNDGNDGNDGNDGNDGND
1
2J9
1
2
3J8
1
2
3J4
1
2
3J5
1
2
3J6
1
2
3J7 1.54 k
R6
D2
(Blue LED)
VCC
GND
1
2
3
4
5
6
7
8
J10
EN
Faultb
DIM01
DIM23
DIM4
DIM5
MODE
GND
GND
1
2
3
J3
VFB
NC
GND
TP4 TP6
TP18TP16TP14TP12TP20TP8TP10
TP22
TP24TP27 TP28 TP29
FS
64.9 k
R8
TP26
TP30
TP31
TP41
TP47
TP42
TP48
TP43
TP49
TP44
TP50
TP45
TP51
TP46
TP52
TP64TP62TP60TP58TP56TP54 TP63TP61TP59TP57TP55TP53
FDD2572
Q1
FDD2572
Q2
FDD2572
Q3
FDD2572
Q4
FDD2572
Q5
FDD2572
Q6
1
R13
NC
R12 1
R15
NC
R14 1
R17
NC
R16 1
R19
NC
R18 1
R21
NC
R20 1
R23
NC
R22
J16J15J14J13J12J11
CH0 CH1 CH2 CH3 CH4 CH5
SE1
SE2
SE3
SE4
SE5
GD1
GD2
GD3
GD4
GD5
DR0
DR1
DR2
DR3
DR4
DR5
CLKOUT
SYNC
TP34TP33
TP36TP35
GND REFRTN
150 k
R2
8.25 k
R4
1 µF
100V
C2
1µF
100V
C1
J0
J1
J2
GND
TP3
TP1 TP2
TP38TP37 TP39 TP40
Power pad of the LM3463 connected to GND
BAV20W-TP
D1 2.94 k
R5
VRAIL
GND
1 µF
16V
C3
VCC
LM3463 Evaluation Board Schematic www.ti.com
3 LM3463 Evaluation Board Schematic
Figure 1. Circuit diagram of the LM3463 evaluation board
4 Bill Of Materials
Designator Description Package Part Number Manufacturer
U1 LED driver LLP-48 LM3463SQ/NOPB Texas Instruments
C1, C2 Capacitor, 1uF, 100V, X7R 1206 GRM31CR72A105KA01L MuRata
C3, C4 Capacitor, 1uF, 16V, X7R 0603 C1608X7R1C105K TDK
C5 Capacitor, 2200 pF, 25V, X7R 0603 GRM188R71E222KA01D MuRata
C6 Capacitor, 0.47uF, 25V, X5R 0603 GRM188R61E474KA12D MuRata
D1 Diode, 200V, 200 mA SOD-123 BAV20W-TP Micro Commercial
D2 Green LED Gull-wing HLMP-6500-F0011 Avago Technologies
J0, J1, J2 Terminal screw vertical, snap- 7693 Keystone
in
J3 3 Pos. connector 100 mil pitch 3-641216-3 TE Connectivity
J4, J5, J6, J7, J8 3 Pos. header 100 mil pitch TSW-103-07-G-S Samtec
J9 2 Pos. header 100 mil pitch TSW-102-07-G-S Samtec
J10 8 Pos. connector 100 mil pitch 3-641216-8 TE Connectivity
J11, J12, J13, J14, Banana jack connector 8.9 mm dia. 575-8 Keystone
J15, j16
Q1, Q2, Q3, Q4, MOSFET, N-CH, 150V, 29A DPAK FDD2572 Fairchild Semiconductor
Q5, Q6
R2 Resistor, 150 kΩ, 1%, 0.1W 0603 CRCW0603150KFKEA Vishay-Dale
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www.ti.com Bill Of Materials
Designator Description Package Part Number Manufacturer
R4 Resistor, 8.25 kΩ, 1%, 0.1W 0603 CRCW06038K25FKEA Vishay-Dale
R5 Resistor, 2.94 kΩ, 1%, 0.1W 0603 CRCW06032K94FKEA Vishay-Dale
R6 Resistor, 1.54 kΩ, 1%, 0.1W 0603 CRCW06031K54FKEA Vishay-Dale
R8 Resistor, 64.9 kΩ, 1%, 0.1W 0603 CRCW060364K9FKEA Vishay-Dale
R10, R37 Resistor, 0Ω, 5%, 0.1W 0603 CRCW06030000Z0EA Vishay-Dale
R13, R15, R17, Resistor, 1.00Ω, 1%, 0.125W 0805 CRCW08051R00FKEA Vishay-Dale
R19, R21, R23
R7, R9, R11 Resistor, 1.00kΩ, 1%, 0.1W 0603 CRCW06031K00FKEA Vishay-Dale
R12, R14, R16, Resistor, 1.00 kΩ, 1%, 0.125W 0603 CRCW08051K00FKEA Vishay-Dale
R18, R20, R22
TP1, TP4, TP6, Terminal, Turret 1502–2 Keystone
TP8, TP10, TP12,
TP14, TP16, TP18,
TP20, TP22, TP24,
TP31, TP33, TP35,
TP37, TP40, TP54,
TP56, TP58, TP60,
TP62, TP64
TP3, TP26, TP27, Orange 5008 Keystone
TP28, TP29, TP30,
TP34, TP36, TP41,
TP42, TP43, TP44,
TP45, TP46, TP47,
TP48, TP49, TP50,
TP51, TP52, TP53,
TP55, TP57, TP59,
TP61, TP63
TP2 Test Point Red 5005 Keystone
TP38 Test Point White 5007 Keystone
TP39 Test Point Black 5006 Keystone
7
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Board Layout www.ti.com
5 Board Layout
Figure 2. Top Layer
Figure 3. Bottom Layer
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Primary power supply
(e.g. AC/DC offline converter, DC power supply)
LM3463 EVALUATION
BOARD
WARNING:
HIGH DC VOLTAGE
J0
J1
J11 J12 J13 J14 J15 J16
J2
J9J5J7
J4J6J8
J10
J3
CH0 CH1 CH2 CH3 CH4 CH5VRAIL
GND
2.5V
VFB
RVFB1
RVFB2
VRAIL
GND
VFB
LM3463 evaluation board
LED strings x 6
Default operation conditions of the board:
IOUT per channel: 200 mA
No. of LED per string: 14 (~3.2V forward voltage per LED)
LED turn on voltage: VRAIL = 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
www.ti.com 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, VRAIL is controlled by the Dynamic Headroom
Control (DHC) circuit of the LM3463 to maintain maximum system efficiency, therefore the VRAIL must have
a wide and adjustable voltage range.
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0
VDHC_READY
VRAIL(nom)
VRAIL(steady)
VRAIL(peak)
VRAIL
Time
Pushed up
by LM3463
Initiated by
primary power
supply
DHC activated
Primary Power Supply www.ti.com
Generally the required range of the VRAIL is determined by the highest and lowest possible forward
voltages of the LED strings (respectively, VLED-MAX-COLD and VLED-MIN-HOT). Since the forward voltage of the
LED strings varies according to the changing of the ambient temperature, the voltage for turning the LEDs
on at system startup must be set higher than the VLED-MAX-COLD. Figure 3 shows the different voltage level of
VRAIL at system startup.
Figure 5. Different voltage levels of the VRAIL at system startup
In Figure 3, the VRAIL is the output voltage of the primary power supply under the control of the LM3463.
VRAIL(peak) is the highest level of VRAIL when the voltage of the OutP pin of the LM3463 equals 0V. VDHC_READY
is the voltage level that the LM3463 turns all output channels on. VRAIL(nom) is the nominal output voltage of
the primary power supply when the OutP pin voltage is higher than VFB+0.6V (i.e. prior to DHC starting)
In order to secure sufficient rail voltage to maintain regulated LED currents when enabling the output
channels, the VRAIL(peak) and VDHC_READY must be set higher than VLED-MAX-COLD (the highest forward voltage of
the LED strings under low ambient temperature). The following settings are suggested to ensure correct
system startup sequence:
1. VRAIL(nom) = VLED-MIN-HOT - 5V
2. VDHC_READY = VLED-MAX-COLD + 5V
3. VRAIL(peak) = VDHC_READY + 5V
Figure 4 shows a suggested procedure to determine the VRAIL(nom), VDHC_READY and VRAIL(peak).
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