Linear Technology LT8391EFE Quick setup guide

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dc2345af
DEMO MANUAL DC2345A
DESCRIPTION
LT8391EFE
60V Synchronous 4-Switch
Buck-Boost Led Controller with Spread Spectrum
Demonstration circuit 2345A is a 60V synchronous
4-switch buck-boost LED controller with spread spectrum
featuringtheLT
®
8391LED driver. It accepts aninputvoltage
from 4V to 60V and drives a single string of LEDs up to
25V at 2A. DC2345A runs at 400kHz switching frequency
without spread spectrum, but spread spectrum frequency
modulation (SSFM) can be enabled with a simple jumper.
SSFM spreads the switching frequency to fsw ±15% for
reduced EMI.
The LT8391 has a wide input voltage range down to 4V and
up to 60V. It has adjustable switching frequency between
150kHz and 600kHz. There is a simple jumper option for
external frequency synchronization, spread spectrum
frequency modulation, or neither.
The LT8391 can be PWM dimmed with an external PWM
signal and an internally-generated PWM signal. DC2345A
has a jumper that can e set to switch between internally-
generated PWM signal, externally-generated PWM signal,
and no PWM signal (100% on). It can be analog dimmed
with a control voltage on either of its two control pins.
LT8391 features both open LED and short LED (LED+ to
GND) protection as well as a fault output flag.
When run with both PWM dimming and spread spectrum,
the spread spectrum aligns itself with the PWM signal for
flicker-free operation.
Small ceramic input and output capacitors are used to save
space and cost. The board is designed with capacitors on
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.
both sides of the synchronous switches for a reduction
in radiated EMI. The open LED overvoltage protection
uses the IC’s constant voltage regulation loop to regulate
the output to approximately 29.7V if the LED string is
opened although it may reach 32V peak during transient
from running LEDs to open. There is a protection diode
from LED+ to GND to prevent negative ringing during a
short-circuit with long wires.
Undervoltage lockout can be adjusted on the circuit with
a few simple resistor choices.
There is an EMI filter on the input of DC2345A. This filter
has a 3.2µH inductor and two 4.7µF capacitors. It is ef-
fective in reducing the conducted EMI in the AM band to
pass CISPR25 class 5 regulations. When run with SSFM,
DC2345A has low conducted EMI.
The LT8391 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 DC2345A. The LT8391EFE is
assembled in a 28-lead plastic TSSOP (FE) package with
a thermally enhanced ground pad. Proper board layout
is essential for maximum thermal performance. See the
data sheet section ‘Layout Considerations’.
Design files for this circuit board are available at
http://www.linear.com/demo/DC2345A

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DEMO MANUAL DC2345A
QUICK START PROCEDURE
Demonstrationcircuit DC2345A is easy to set upto evaluate
theperformanceof the LT8391 Follow the procedurebelow:
1. With power off, connect a string of LEDs that will run
with forward voltage less than or equal to 25V(at 2A)
to the LED+ and GND banana jacks on the PCB as
shown in Figure 1.
2. Connect the EN/UVLO terminal to GND.
3. Set JP1 to EXT/ON and JP3 to ON for 100% always-on
LED operation. Set JP2 to NO SPREAD/SYNC to run
without SSFM or external synchronization.
4. With power off, connect the input power supply to the
EMIVIN and GND banana jacks. Make sure that the DC
input voltage will not exceed 60V.
5. Turn the input power supply on and make sure the
voltage is between 4V and 60V for proper operation.
6. Release the EN/UVLO-to-GND connection.
7. Observe the LED string running at the programmed
LED current.
8. To change the brightness with analog dimming, simply
attach a voltage source to either the CTRL1 or CTRL2
terminal and set the voltage between 0V and 1.5V. See
data sheet for details.
9. To change brightness with external PWM dimming, set
JP1 to EXT/ON and JP3 to EXT. Attach a 3V rectangular
waveform with varying duty cycle to the PWM terminal.
10. To change brightness with internally-generated PWM
dimming, set JP1 to INT and JP3 to INT. Adjust the
setting of the VR1 variable resistor with a small flat-
head screwdriver to toggle between 0% and 100%
PWM dimming duty cycle in 1/128 steps.
11. To enable spread spectrum frequency modulation, set
JP2 to SPREAD ON.
PERFORMANCE SUMMARY
Specifications are at TA= 25°C
PARAMETER CONDITIONS MIN TYP MAX
Input Voltage EMIVIN Range Operating VLED = 25V 4V 60V
Switching Frequency R3 = 100k 400kHz
ILED R1 = 0.05Ω 7.0V < PVIN < 60V VLED = 25V 2.0A
VLED range R5 = 1M R6 = 34.8k 26V
Open LED Voltage VOUT R5 = 1M R6 = 34.8k 29.7V
Typical Efficiency (100% PWM DC) PVIN = 14V VLED = 25V ILED = 2.0A 97%
Internally-Generated PWM Dimming Range Operating JP3 = INT JP1 = INT 1/128 100%
Internally-Generated PWM Dimming Frequency Operating JP3 = INT JP1 = INT R16 = 200k 200Hz
Peak Switch Current Limit Boost Region R2 = 0.004Ω 12.5A
Peak Switch Current Limit Buck Region R2 = 0.004Ω 12.5A

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DEMO MANUAL DC2345A
QUICK START PROCEDURE
Figure 1. Test Procedure Setup Drawing for DC2345A
SET JP2 FOR SPREAD SPECTRUM
OR EXTERNAL SYNCHRONIZATION
OPTIONAL EXTERNAL
FREQUENCY SYNC
DC2345A F01
OPTIONAL CTRL2
ANALOG DIMMING
FLOAT OKAY
OPTIONAL
CTRL1 ANALOG
DIMMING FLOAT
OKAY
OPTIONAL CONNECT TO
GND FOR SHUTDOWN
FLOAT = ENABLE
SET JP3 FOR PWM DIMMING TYPE
ON = 100% ON WITH NO PWM DIM
INT = INTERNAL PWM DIMMING SET WITH JP1
AND VR1
EXT = EXTERNAL PWM DIMMING SET WITH JP1
AND PWM INPUT
NOTE: SET JP1 TO MATCH JP3
OPTIONAL
PWM INPUT
FOR EXTERNAL
PWM DIMMING
+–
IIN
+–
ILED
VIN
+
–
+
–
VOUT
+
–
+
–

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DEMO MANUAL DC2345A
ILED (A)
EFFICIENCY (%)
VIN (V)
600
100
70
3
0
10 20 30 40 50
75
80
90
85
95
0.5
1
2
1.5
2.5
EFFICIENCY
BOOST BUCK
BUCK-BOOST
VLED = 25V
ILED = 2A
fSW = 400kHz
ILED
5µs/DIV
IL1
1A/DIV
ILED
1A/DIV
INFINITE PERSIST
VIN = 24V
VLED = 25V
SPREAD SPECTRUM ON
1000:1 DIMMING: EXTERNAL PWM SOURCE, 120Hz
10µs/DIV
IL1
1A/DIV
ILED
1A/DIV
INFINITE PERSIST
VIN = 24V
VLED = 25V
SPREAD SPECTRUM ON
128:1 DIMMING: INTERNAL PWM DIMMING, 200Hz
QUICK START PROCEDURE
Figure 2. DC2345A Efficiency and LED Current Versus Input Voltage for 25V 2A LED Load.
Efficiency Peaks at 98% and Doesn’t Stray Far from That Peak, Ranging from 95% to 97%
Throughout the Typical 9V-16V Automotive Input Range. Also Shown, the LT8391 Peak
Inductor Current Limit Can Maintain Stable Output with Reduced Output Power at Low VIN.
Figure 3. Infinite-Persist Scope Traces Show PWM Dimming and SSFM Working Together for
Flicker-Free Brightness Control with Both Externally and Internally Generated PWM Dimming.

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DEMO MANUAL DC2345A
PARTS LIST
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
Required Circuit Components
1 2 C1, C2 CAP., CER., 4.7µF, X7S, 100V, 10%, 1206 AVX, 12061Z475KAT2A
2 2 C3, C4 CAP., CER., 10µF, X5R, 50V, 10%, 1206 MURATA, GRM31CR61H106KA12L
3 1 C5 CAP., CER., 1µF, X5R, 50V, 10%, 0603 MURATA, GRM188R61H105KAALD
4 1 C6 CAP., CER., 1µF, X7S, 100V, 10%, 0805 TDK, C2012X7S2A105K125AB
5 1 C7 CAP., CER., 0.47µF, X7R, 16V, 10%, 0603 MURATA, GRM188R71C474KA88D
6 3 C8, C11, C12 CAP., CER., 0.1µF, X7R, 16V, 10%, 0603 MURATA, GRM188R71C104KA01D
7 2 C9, C17 CAP., CER., 10nF, X7R, 16V, 10%, 0603 AVX, 0603YC103KAT2A
8 1 C10 CAP., CER., 4.7µF, X5R, 10V, 10%, 0603 MURATA, GRM188R61A475KE15D
9 1 L1 IND., 4.7µH, 13.00 ×12.80mm WURTH ELEKTRONIK, 7443550480
10 1 M1 MOSFET, 60V, TDSON-8 INFINEON, BSC067N06LS3
11 1 M2 MOSFET, 60V, TDSON-8 INFINEON, BSC100N06LS3
12 2 M3, M4 MOSFET, 40V, TDSON-8 INFINEON, BSC093N04LS
13 1 M5 MOSFET, P-CH, 40V, POWERPAK-1212-8 VISHAY, SI7611DN-T1-GE3
14 1 R1 RES,. SENSE, 0.05Ω, 1W, 1%, 2010 TT Electronics, LRC-LR2010LF-01-R050F
15 1 R2 RES,. SENSE, 0.004Ω, 1W, 1%, 2010 ROHM, PMR50HZPFV4L00
16 1 R3 RES, CHIP, 100k, 1/10W, 5%, 0603 VISHAY, CRCW0603100K0JNEA
17 1 R4 RES, CHIP, 2.2k, 1/10W, 1%, 0603 VISHAY, CRCW06032K20FKEA
18 1 R5 RES, CHIP, 1M, 1/10W, 1%, 0603 VISHAY, CRCW06031M00FKEA
19 1 R6 RES, CHIP, 34.8k, 1/10W, 1%, 0603 VISHAY, CRCW060334K8FKEA
20 1 R9 RES, CHIP, 5.1, 1/10W, 5%, 0603 VISHAY, CRCW06035R10JNEA
21 1 R26, R27 RES, CHIP, 10Ω, 1/10W, 5% 0603 VISHAY, CRCW060310R0FKEA
22 1 U1 I.C., LED CONTROLLER, TSSOP28FE-EA LINEAR TECH., LT8391EFE#PBF
Optional Electrical Components
1 1 C13 CAP., ALUM., 33µF, 63V, 20%, 8 × 10.2mm SUN ELECTRONIC INDUSTRIES CORPORATION,
63CE33BS
2 2 C14, C15 CAP., CER., 4.7µF, X7S, 100V, 10%, 1206 AVX, 12061Z475KAT2A
3 1 C16 CAP., CER., 0.1µF, X5R, 100V, 10%, 0402 MURATA, GRM155R62A104KE14D
4 0 C18, C19, C20, C21 (OPT) CAP., OPTION, 0603
5 1 D1 DIODE, SCHOTTKY, 60V, 1A, SOD323F NXP, PMEG6010CEJ,115
6 0 D2 (OPT) DIODE, ZENER, 5.1V, 250MW, SOD323 CENTRAL SEMI., CMDZ5231B TR
7 0 FB1 (OPT) CHIP BEAD, OPTION, 1206
8 1 L2 IND., 3.2µH, 13.00 × 12.80mm WURTH ELEKTRONIK, 7443550320
9 3 R10, R11, R15 RES, CHIP, 100k, 1/10W, 5%, 0603 VISHAY, CRCW0603100K0JNEA
10 1 R7 RES, CHIP, 499k, 1/10W, 1%, 0603 VISHAY, CRCW0603499KFKEA
11 1 R8 RES, CHIP, 221k, 1/10W, 1%, 0603 VISHAY, CRCW0603221KFKEA
12 0 R12, R13, R14, R17, R18,
R19, R20, R23 (OPT)
RES., OPTION, 0603
13 1 R16 RES, CHIP, 200k, 1/10W, 1%, 0603 VISHAY, CRCW0603200KFKEA
14 3 R21, R24, R25 RES, CHIP, 0Ω, 1/10W, 1%, 0603 VISHAY, CRCW06030000Z0EA
15 1 R22 RES, CHIP, 91k, 1/10W, 5%, 0603 VISHAY, CRCW060391K0FKEA
16 1 VR1 TRIMMER., 100k, 0.25W, SMD Bourns, 3314J-1-104E

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DEMO MANUAL DC2345A
PARTS LIST
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
Additional Hardware
1 4 E1, E2, E10, E11 TEST POINT, TURRET, .094" MTH HOLE MILL-MAX, 2501-2-00-80-00-00-07-0
2 9 E3, E4, E5, E6, E7, E8, E9,
E12, E13
TEST POINT, TURRET, .061" MTG. HOLE MILL-MAX, 2308-2-00-80-00-00-07-0
3 1 JP1 CONN., HEADER, 1 × 3, 2mm WURTH ELEKTRONIK, 62000311121
4 2 JP2, JP3 CONN., HEADER, 2 × 3, 2mm WURTH ELEKTRONIK, 62000621121
5 3 XJP1, XJP2, XJP3 SHUNT, 2mm WURTH ELEKTRONIK, 60800213421
6 4 J1, J2, J3, J4 CONN., JACK, BANANA, Non-Insulated, 0.218" KEYSTONE, 575-4

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DEMO MANUAL DC2345A
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 representa-
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
SCHEMATIC DIAGRAM

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DEMO MANUAL DC2345A
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
[phone] ●FAX: [phone] ●www.linear.com
© LINEAR TECHNOLOGY CORPORATION 2016
LT 0516 • PRINTED IN USA
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

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