DC1666A - Demo Manual

DEMO MANUAL DC1666A
LT3791
Four-Switch Buck-Boost
LED Driver Controller
Description
Demonstration circuit DC1666A is a synchronous fourswitch buck-boost LED driver controller. It accepts an
input voltage from 4.7V to 60V, and drives up to 25V of
LEDs at 2A. DC1666A features both PWM and analog
dimming of the LED string. It has an OPENLED flag that
indicates when the LED string has been removed and it
has a SHORTLED flag that indicates that the output has
been shorted to GND. In both cases, the IC remains in
control and well protected.
DC1666A features very high efficiency at 300kHz switching
frequency and continuous conduction mode (CCM). The
synchronous four-switch topology both steps up and steps
down voltage while regulating up to 50W of constant LED
output current at efficiencies up to 98%. The circuit can
be altered for applications requiring over 100W of LEDs.
An optional SYNC terminal is provided for synchronizing
to an external clock and CLKOUT terminal provides a
source to sync another converter to the internal clock of
the LT®3791.
Three sense resistors provide constant output current
control and monitoring, peak switch current control, and
DC input current limit and monitoring. The ISMON and
IVINMON outputs tell the user how much current is flowing
through the output and input sense resistors.
Small ceramic input and output capacitors are used to
save space and cost. The open LED overvoltage protection
uses the ICs constant voltage regulation loop to limit the
output to approximately 28.3V if the LED string is opened.
For low input voltage operation, the CTRL pin voltage is
reduced as the input voltage drops below 6.5V, reducing
LED brightness and restraining the peak switch currents
in order to limit inductor and switch size. UVLO turns the
LEDs off when VIN drops below 4.7V. When input rises
above 57.6V, overvoltage lockout turns the switches off
to protect them and they turn back on when VIN drops
below 56.2V.
DC1666A PWM dimming is simple. The PWM dimming
MOSFET turns the LED string on and off with an input to
the PWM dimming terminal. For the highest PWM dimming
ratio, it is recommended to use 100Hz as a PWM dimming
frequency. Information regarding PWM dimming ratios and
performance can be found in the Applications Information
section of the LT3791 data sheet. Analog dimming is also
simple with a simple voltage source on the CTRL terminal.
Modifications can be made to DC1666A in order to convert
the board to higher or lower power or from an LED driver
to a constant voltage regulator or battery charger. Please
consult the factory or the LT3791 data sheet for details.
The LT3791 data sheet gives a complete description of
the part, operation and applications information. The
data sheet must be read in conjunction with this demo
manual for demonstration circuit DC1666A. The LT3791
is assembled in a 38-lead plastic TSSOP package with
a thermally enhanced ground pad. Proper board layout
is essential for maximum thermal performance. See the
Layout Considerations section in the data sheet.
Design files for this circuit board are available at
http://www.linear.com/demo
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
dc1666af
1
DEMO MANUAL DC1666A
Performance Summary
(TA = 25°C)
PARAMETER
CONDITION
VALUE (TYPICAL)
Input Voltage PVIN Range*
Operating
4.7V to 60V*
Switching Frequency
R12 = 86.6k
300kHz
ILED
CTRL = Float, 7V < PVIN < 57.6V
2.0A
VLED Range
R7 = 1M, R9 = 44.2k
9.5V < VLED < 25.5V
Open LED Voltage
R7 = 1M, R9 = 44.2k
28.3V
Typical Efficiency Boost Region
PVIN = 20V, VLED = 25V, ILED = 2A
97.5%
Typical Efficiency Buck-Boost Region
PVIN = 24V, VLED = 25V, ILED = 2A
96.8%
Typical Efficiency Buck Region
PVIN = 30V, VLED=25V, ILED = 2A
97.3%
Undervoltage Lockout (Falling Turn-Off)
R13 = 332k and R6 = 115k
4.7V
Undervoltage Lockout (Rising Turn-On)
R13 = 332k and R6 = 115k
5.7V
Overvoltage Lockout (Rising Turn-Off)
R11 = 54.9k, R19 = 1M
57.6V
Overvoltage Lockout (Falling Turn-On)
R11 = 54.9k, R19 = 1M
56.2V
Peak Switch Current Limit Boost Region
RS = 0.004Ω
11A
Valley Switch Current Limit Buck Region
RS = 0.004Ω
10A
* The guaranteed input voltage range of the LT3791 is 4.7V to 60V. Overvoltage lockout is set externally at 57.6V on this demo circuit to protect the 60V
MOSFETs M1 and M2. Overvoltage lockout is adjustable.
dc1666af
2
DEMO MANUAL DC1666A
Quick Start Procedure
Demonstration circuit DC1666A is easy to set up to evaluate
the performance of the LT3791. Follow the procedure below:
5.Turn the input power supply on and make sure the
voltage is between 4.7V and 60V.
NOTE: PWM must be pulled high to run. If PWM is not
used, connect PWM to a 5V source or to INTVCC on the
PCB using 0Ω resistor R22.
6.Release the EN/UVLO to GND connection.
1. Connect a string of LEDs that will run with forward voltage less than 25.5V, but greater than 9.5V, to the LED+
and LED– terminals on the PCB as shown in Figure 1.
2.Connect the EN/UVLO terminal to GND.
3.With power off, connect the input power supply to the
PVIN and GND terminals. Make sure that the PVIN DC
input voltage will not exceed 60V.
7.Observe the LED string running at the programmed
LED current.
8. For PWM dimming, connect a PWM (100Hz or higher is
recommended) signal to the PWM terminal. For analog
dimming, connect a DC voltage between 0V and 2V to
the CTRL terminal.
9.Observe the reduction of brightness in the LED string
when PWM or analog dimming.
4. Connect the PWM terminal. If PWM is not used, connect
PWM to a 5V source or to INTVCC on the PCB using 0Ω
resistor R22. PWM must be pulled high to run.
dc1666af
3
DEMO MANUAL DC1666A
quick start procedure
Figure 1. Test Procedure Setup Drawing for DC1666A
dc1666af
4
DEMO MANUAL DC1666A
quick start procedure
100
98
EFFICIENCY (%)
96
BOOST
BUCK
94
BUCK-BOOST
92
90
88
86
84
82
80
10
0
30
40
20
INPUT VOLTAGE (V)
60
50
3791 TA02b
Figure 2. DC1666A Efficiency with 25V LEDs at 2A
PWM
5V/DIV
IL1
2A/DIV
ILED
2A/DIV
50µs/DIV
3791 TA02c
Figure 3. DC1666A 100Hz 50:1 PWM Dimming
Waveforms at 12VIN and 25VLED at 2A
2.0
TURN-ON
(FALLING)
ILED (A)
1.5
UVLO
(FALLING)
1.0
TURN-ON
(RISING)
OVLO
(RISING)
0.5
0
3
4
5
6
9
7
8
INPUT VOLTAGE (V)
10 50
55
60
DC1666A F04
Figure 4. DC1666A CTRL LED Current Foldback at Low VIN with UVLO Falling and Rising and OVLO
dc1666af
5
DEMO MANUAL DC1666A
Parts List
ITEM
QTY
REFERENCE
PART DESCRIPTION
MANUFACTURER/PART NUMBER
Required Electrical Components
1
1
CSS
CAP X7R 0.01µF 50V 10% 0603
AVX, 06035C103KAT2A
2
1
CC
CAP X7R 0.022µF 50V 10% 0603
AVX, 06035C223KAT2A 5%
3
4
C2, C3, C12, C14
CAP X7R 2.2µF 100V 10% 1210
AVX, 12101C225KAT2A
4
1
C5
CAP X7R 1µF 100V 10% 1206
AVX, 12061C105KAT2A
5
3
C6, C8, C11
CAP X5R 0.1µF 16V 10% 0402
AVX, 0402YD104KAT2A
6
1
C7
CAP X5R 4.7µF 10V 10% 0603
AVX, 0603ZD475KAT2A
7
4
C9, C10, C13, C15
CAP X7R 4.7µF 50V 10% 1210
AVX, 12105C475KAT2A
8
2
D1-D2
DIODE Single Schottky Barrier Diode SOD-323
NXP, BAT46WJ
9
1
L1
INDUCTOR 10µH
Cooper Bussmann, HC9-100-R
10
2
M1, M2
MOSFET N-Channel 60V LFPAK
RENESAS, RJK0651DPB-00-J5
11
2
M3, M4
MOSFET N-Channel 40V LFPAK
RENESAS, RJK0451DPB-00-J5
12
1
M5
MOSFET N-Channel 40V SOT-23
VISHAY, Si2318DS-T1-E3
13
1
RLED
RES CHIP 0.050Ω 1% 2010
VISHAY, WSL2010R0500FEA
14
1
RS
RES CHIP 0.004Ω 1W 1% 2010
VISHAY, WSL20104L000FEA
15
1
R7
RES CHIP 1M 1% 0402
VISHAY, CRCW04021M00FKED
16
1
R9
RES CHIP 44.2k 1% 0402
VISHAY, CRCW040244K2FKED
17
1
R12
RES CHIP 86.6k 1% 0402
VISHAY, CRCW040286K6FKED
18
1
U1
IC LT3791EFE 38-LEAD TSSOP VERSION AA TSSOP
LINEAR, LT3791EFE#PBF
Optional Electrical Components
1
1
C4
CAP X5R 0.47µF 6.3V 10% 0402
AVX, 04026D474KAT2A
2
0
C16, C17
CAP 1210
OPTIONAL
3
0
C18
CAP 0603
OPTIONAL
4
0
D3, D4
DIODE SMB
OPTIONAL
5
2
RC, R16
RES CHIP 0Ω 0402
VISHAY, CRCW04020000Z0ED
6
1
RIN
RES CHIP 0.003Ω 1W 1% 1206
IRC, ULR-G-1-1206-R003-1-LF-SLT
7
1
R2
RES CHIP 0Ω 1206
VISHAY, CRCW12060000Z0EA
8
1
R3
RES CHIP 1M 1% 0402
VISHAY, CRCW04021M00FKED
9
2
R4, R5
RES CHIP 200k 5% 0603
VISHAY, CRCW0603200KJNEA
10
1
R6
RES CHIP 115k 1% 0603
VISHAY, CRCW0603115KFKEA
11
1
R8
RES CHIP 237k 1% 0402
VISHAY, CRCW0402237KFKED
12
0
R10, R15, R18, R20, R21 RES CHIP 0402Ω 0402
OPTIONAL
13
1
R11
RES CHIP 54.9k 1% 0402
VISHAY, CRCW040254K9FKED
14
1
R13
RES CHIP 332k 1% 0402
VISHAY, CRCW0402332KFKED
15
1
R14
RES CHIP 0Ω 0603
VISHAY, CRCW06030000Z0EA
16
1
R17
RES CHIP 51Ω 5% 0402
VISHAY, CRCW040251R0JNED
17
1
R19
RES CHIP 1M 1% 0603
VISHAY, CRCW06031M00FKED
18
0
R22, R23
RES CHIP 0Ω 0603
OPTIONAL
22
E1-E22
TURRET 0.095
MILL-MAX, 2501-2-00-80-00-00-07-0
Hardware
1
dc1666af
6
D
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
A
B
C
E21
E19
E20
E15
E13
E12
E11
E10
R4
200k
0603
E9
E17
E8
E4
R14
0
0603
5
ALL CAPACITORS ARE 0603.
ALL RESISTORS ARE 0402.
R19
1M
VREF
9
R13
332k
Css
10nF
RIN
R17
51
0.003
0402
C4 470nF
1210
IVINMON
SS
SYNC
CLKOUT
4
U1
Cc
22nF
Rc
0
OPENLED
ISMON
12
PWM
PWMOUT
ISN
ISP
FB
TG2
SW2
BG2
SNSN
SNSP
BG1
SW1
TG1
BST2
BST1
INTVCC
R16
3
31
26
25
37
24
21
19
28
27
18
16
14
22
15
13
0
C7
4.7uF
10V
0603
C12
2.2uF
100V
1210
3
3
C16
(OPT)
C18
OPT
D4
OPT
D2
BAT46WJ
M3
RJK0451DPB
SUMIDA
HC9-100-R
L1 10uH
C6
0.1uF
0402
D1
BAT46WJ
C14
2.2uF
100V
1210
C8
0.1uF
0402
OPT INTVCC
RS
0.004
2010
M2
RJK0651DPB
D3
OPT
M1
RJK0651DPB
0603
R22
C3
2.2uF
100V
1210
R15 OPT
C2
2.2uF
100V
1210
C5
1uF
100V
1206
R2
0
1206
LT3791EFE
SHORTLED
VREF
NC
CTRL
OVLO
EN/UVLO
R12
86.6k
300kHz
2
34
33
7
8
4
5
6
23
1
38
R6
115k
0603
R20 OPT
VREF
0402
C11
0.1uF
R18
OPT
R11
54.9k
R10
OPT
R8
237k
OPENLED
R5
200k
0603
INTVCC
R3
1M
PVIN
NOTE: UNLESS OTHERWISE SPECIFIED
GND
GND
SYNC
CLKOUT
ISMON
IVINMON
OPENLED
SHORTLED
CTRL
OVLO
EN/UVLO
GND
E1
4
RT
35
VC
36
PVIN
4.7V - 60V
10
IVINP
11
IVINN
TEST1
29
SGND
30
PGND
39
PGND
VIN
32
TEST2
PGND
20
R23 OPT
0603
M4
RJK0451DPB
2
M6
OPT
C13
4.7uF
50V
1210
C15
4.7uF
50V
1210
INTVCC
OPENLED
C10
4.7uF
50V
1210
R21
OPT
C9
4.7uF
50V
1210
R9
44.2k
R7
1M
2
M5
0.05
2010
RLED
INTVCC
GND
VIN
4.7V - 60V
1
Si2318DS
C17
(OPT)
E5
E3
E2
1
LED+
OUT
E22
E7
E18
E16
GND
PWM
GND
LED-
E14 2A
E6
A
B
C
D
Schematic Diagram
17
5
DEMO MANUAL DC1666A
dc1666af
7
DEMO MANUAL DC1666A
DEMONSTRATION BOARD IMPORTANT NOTICE
Linear Technology Corporation (LTC) provides the enclosed product(s) under the following AS IS conditions:
This demonstration board (DEMO BOARD) kit being sold or provided by Linear Technology is intended for use for ENGINEERING DEVELOPMENT
OR EVALUATION PURPOSES ONLY and is not provided by LTC for commercial use. As such, the DEMO BOARD herein may not be complete
in terms of required design-, marketing-, and/or manufacturing-related protective considerations, including but not limited to product safety
measures typically found in finished commercial goods. As a prototype, this product does not fall within the scope of the European Union
directive on electromagnetic compatibility and therefore may or may not meet the technical requirements of the directive, or other regulations.
If this evaluation kit does not meet the specifications recited in the DEMO BOARD manual the kit may be returned within 30 days from the date
of delivery for a full refund. THE FOREGOING WARRANTY IS THE EXCLUSIVE WARRANTY MADE BY THE SELLER TO BUYER AND IS IN LIEU
OF ALL OTHER WARRANTIES, EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING ANY WARRANTY OF MERCHANTABILITY OR FITNESS
FOR ANY PARTICULAR PURPOSE. EXCEPT TO THE EXTENT OF THIS INDEMNITY, NEITHER PARTY SHALL BE LIABLE TO THE OTHER FOR
ANY INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES.
The user assumes all responsibility and liability for proper and safe handling of the goods. Further, the user releases LTC from all claims
arising from the handling or use of the goods. Due to the open construction of the product, it is the user’s responsibility to take any and all
appropriate precautions with regard to electrostatic discharge. Also be aware that the products herein may not be regulatory compliant or
agency certified (FCC, UL, CE, etc.).
No License is granted under any patent right or other intellectual property whatsoever. LTC assumes no liability for applications assistance,
customer product design, software performance, or infringement of patents or any other intellectual property rights of any kind.
LTC currently services a variety of customers for products around the world, and therefore this transaction is not exclusive.
Please read the DEMO BOARD manual prior to handling the product. Persons handling this product must have electronics training and
observe good laboratory practice standards. Common sense is encouraged.
This notice contains important safety information about temperatures and voltages. For further safety concerns, please contact a LTC application engineer.
Mailing Address:
Linear Technology
1630 McCarthy Blvd.
Milpitas, CA 95035
Copyright © 2004, Linear Technology Corporation
dc1666af
8
Linear Technology Corporation
LT 0312 • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900
●
FAX: (408) 434-0507 ● www.linear.com
 LINEAR TECHNOLOGY CORPORATION 2012
Similar pages