DC2361A - Demo Manual

DEMO MANUAL DC2361A
LT3952EFE
2MHz 60V LED Driver with
Internal 4A Switch
DESCRIPTION
Demonstration circuit DC2361A is a 2MHz 60V LED driver
with internal 4A switch featuring the LT3952 monolithic
LED driver. It accepts an input voltage from 8V to 28V
(with transient to 36V) and boosts to a single string of
LEDs up to 40V at 330mA. DC2361A features an integrated
4A switch, constant current and constant voltage output
control as well as input current limit and monitoring.
The LT3952 has a wide input voltage range down to 3V
and up to 42V. It has adjustable switching frequency
between 200kHz and 3MHz. It has an option for external
frequency synchronization or spread spectrum frequency
modulation. It has high PWM dimming capability from an
external signal and can be PWM dimmed with an internally
generated PWM oscillator and analog input signal. It can
be analog dimmed with a control voltage on its control
pin. LT3952 features both open LED and short LED (LED+
to GND) protection as well as fault output flags for each.
Although DC2361A is assembled as a boost LED driver,
it can be altered to be run as a buck mode, buck-boost
mode or boost-buck LED driver.
There is another demonstration circuit featuring LT3952
at 350kHz (DC2013A).
DC2361A features an option to turn on spread spectrum
by simply changing the position of a jumper from NO
SPREAD to SPREAD or to EXTERNAL SYNC.
Small ceramic input and output capacitors are used to save
space and cost. The open LED overvoltage protection uses
the IC’s constant voltage regulation loop to regulate the
output to approximately 45V if the LED string is opened
although it may reach 49V peak during transient from
running LEDs to open. There is a protection diode from
LED+ to GND to prevent negative ringing during a shortcircuit with long wires.
There is undervoltage and overvoltage lockout that can be
adjusted on the circuit with a few simple resistor choices.
There is a small EMI filter on the input of DC2361A. This
EMI filter has a ferrite bead and very small cap to reduce
high frequency EMI. The PCB layout contains a small
hot-loop for minimized very high frequency EMI. The EMI
filter can be used by connecting to the ‘EMI VIN’ terminal.
However, if the EMI filter is not needed, the input connection can be directly to the PVIN terminal. If the EMI filter
is not used, it is recommended to remove the EMI filter if
EMI measurements are being made from the PVIN terminal
for base EMI testing. It can be replaced for EMI testing at
the EMI VIN terminal.
The LT3952 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 DC2361A. The LT3952EFE 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
Layout Considerations section.
Design files for this circuit board are available at
http://www.linear.com/demo/DC2361A
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.
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DEMO MANUAL DC2361A
PERFORMANCE SUMMARY
Specifications are at TA = 25°C
PARAMETER
CONDITIONS
MIN
Input Voltage PVIN and EMI VIN Range
Operating VIN = PVIN VLED > 36V
8V
TYP
MAX
28V
Switching Frequency
R5 = 40.2k
2MHz
ILED
R1 = 0.75Ω 8.0V < PVIN < 36V VLED > 36V
333mA
VLED range
R2 = 1M R3 = 26.7k
Open LED Voltage VOUT
R2 = 1M R3 = 26.7k
43.5V
Typical Efficiency (100% PWM DC)
90%
Input Under Voltage Lockout (Falling Turn-Off)
PVIN = 14V VLED = 40V ILED = 333mA
R7 = 499k R8 = 71.5k R9 = 25.5k
Input Under Voltage Lockout (Rising Turn-On)
R7 = 499k R8 = 71.5k R9 = 25.5k
9.1V
VISMON
Operating ILED = 330mA
1.0V
Peak Switch Current Limit
Operating
4A
Demonstration circuit 2361A is easy to set up to evaluate
the performance of the LT3952 Follow the procedure below:
5. Release the EN/UVLO-to-GND connection.
PVIN
40V
7.6V
QUICK START PROCEDURE
1. Connect a string of LEDs that will run with forward voltage less than or equal to 40V (at 330mA), but greater
than PVIN, to the LED+ and GND terminals on the PCB
as shown in Figure 1.
6. Observe the LED strings running at the programmed
LED current.
2. Connect the EN/UVLO terminal to GND.
7. To change the brightness with analog dimming, simply
attach a voltage source to the CTRL terminal and set
the voltage between 0V and 1.5V. See data sheet for
details.
3. With power off, connect the input power supply to the
EMI VIN (or PVIN) and GND terminals. Make sure that
the DC input voltage will not exceed 28V (or VLED).
8. To change brightness with external PWM dimming,
attach a 3V rectangular waveform with varying duty
cycle to the PWM terminal.
4. Turn the input power supply on and make sure the
voltage is between 8V and 28V (or VLED) for proper
operation.
9. To enable spread spectrum frequency modulation,
simply change the position of the shunt on the SYNC/
SPRD jumper to the SPREAD SPECTRUM position.
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DEMO MANUAL DC2361A
DEMO CIRCUIT OPTIONS
Demonstration circuit 2361A can be adjusted for higher
or lower output voltage, different LED current, or different
topology. The following options are for simple changes
to the demonstration circuit. The data sheet gives more
information regarding designing with the LT3952. For
more information, see the data sheet for details or contact
Linear Tech customer support.
regulator. Output voltage should remain below 60V when
used as a constant voltage device.
MAXIMUM LED VOLTAGE
A change in LED current or input voltage may lead to higher
or lower maximum switch current. The maximum switch
current for this converter is 4A and is fixed internally.
DC2361A is set for 44V of overvoltage protection and the
maximum LED string voltage used on the standard build
should be 40V. LT3952 output voltage can be set higher
with an adjustment to the OVP resistors. When raising
output voltage, be sure not to violate the maximum duty
cycle limit at 2MHz (or adjusted frequency), the 60V abs
max output voltage of the part (including open LED output
overshoot), and 4A peak switch current limit at low VIN.
See data sheet for details.
CURRENT OR VOLTAGE REGULATION
The LT3952 can be used for constant current or voltage
regulation. If the load placed on the LED+ to GND terminals
allows VOUT to climb high enough for V(ISP-ISN)=1.2V,
then the voltage regulation loop of the converter takes over.
In this case, the compensation for a given channel should
be adjusted for proper use as a constant voltage regulator.
The IC can be used as a boost or SEPIC constant voltage
LED CURRENT
LED current on DC2361A is set for 330mA with 0.75Ω
resistor R1. For a different maximum LED current, change
this resistor. 250mV/RLED = ILED.
OVERVOLTAGE PROTECTION
Overvoltage protection is set with the resistor pair R2 and
R3 for the boost topology. For buck mode, buck-boost
mode, and boost-buck see data sheet for details how to
set the feedback resistors. Note that R19, R20, R21, and
Q1 are provided as optional placeholders on the demonstration circuit for simple feedback resistor changes for
these topologies.
UNDERVOLTAGE AND OVERVOLTAGE LOCKOUT
UVLO and OVLO can be adjusted by changing the values
of R7, R8 and R9.
Resistors R10 and R11 are available for setting UVLO and
OVLO separately.
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DEMO MANUAL DC2361A
DEMO CIRCUIT OPTIONS
–
ILED
+
CONNECT POWER TO
EITHER PVIN OR TO EMI VIN
IIN
+
–
VOUT
–
+
POWER
SUPPLY
+
–
+
VIN
–
+
–
+
–
OPTIONAL
SHUTDOWN
SELECT JPI SETTING
3V
3V
0V
0V
EXTERNAL SYNC OPTION
0V
3V
OPTIONAL
ANALOG DIMMING
OPTIONAL
EXTERNAL PWM
Figure 1. Test Procedure Setup Drawing for DC2361A
Figure 2. DC2361A 12VIN 120Hz PWM Dimming Waveforms at Different PWM Duty Cycles with 5000:1 in Bold.
ILED Waveform (200mA/Div) Is on the Bottom (with 40V LED String) and IL1 Waveform (2A/Div) Is on the Top.
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DEMO MANUAL DC2361A
DEMO CIRCUIT OPTIONS
0.400
0.300
0.250
0.200
0.150
0.100
0.050
0.000
6
7
8
9
10
PVIN (V)
11
12
13
14
24
25
26
27
PVIN (V)
28
29
30
Figure 3. DC2361A UVLO and OVLO Falling and Rising
100%
95%
EFFICIENCY (%)
LED CURRENT (A)
0.350
90%
85%
80%
75%
70%
0
5
10
15
PVIN (V)
20
25
30
Figure 4. DC2361A Efficiency at Maximum ILED vs PVIN with 40V LEDs (at 330mA)
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DEMO MANUAL DC2361A
PARTS LIST
ITEM
QTY
REFERENCE
PART DESCRIPTION
MANUFACTURER/PART NUMBER
MURATA, GRM31CR61H106KA12L
Required Circuit Components
1
1
C1
CAP., 10μF, X5R, 50V, 10%, 1206
2
1
C2
CAP., 1μF, X7R, 50V, 10%, 0805
MURATA, GRM21BR71H105KA12L
3
1
C3
CAP., 0.1μF, X7R, 10V, 10%, 0402
MURATA, GRM155R71A104KA01D
4
1
C4
CAP., 1000pF, X5R, 10V, 10%, 0402
MURATA, GRM155R61A102KA01D
5
1
C5
CAP., 2.2μF, X5R, 6.3V, 10%, 0603
MURATA, GRM188R60J225KE19D
6
1
C6
CAP., 4.7μF, X7R, 50V, 10%, 1206
MURATA, GRM31CR71H475KA12L
7
1
D1
DIODE, SCHOTTKY, RECTIFIER, 60V, 1A,SOD-123F
NXP, PMEG6010CEH,115
8
1
L1
IND., PWR., 2.2μH, 20%, 4020
Würth Elektronik, 74437324022
9
1
M1
XSTR., MOSFET, P-CH, 60V, SOT-23
VISHAY, Si2309CDS-T1-GE3
10
1
R1
RES., 0.75Ω, 1/2W, 1%, 1206
SUSUMU, RL1632R-R750-F
11
1
R2
RES., 1M, 1/10W, 1%, 0603
VISHAY, CRCW06031M00FKEA
PANASONIC, ERJ3EKF1004V
12
1
R3
RES., 26.7k, 1/16W, 1%, 0402
VISHAY, CRCW040226K7FKED
13
1
R4
RES., 10k, 1/16W, 5%, 0402
VISHAY, CRCW040210K0JNED
14
1
R5
RES., 40.2k, 1/16W, 1%, 0402
VISHAY, CRCW040240K2FKED
15
1
U1
I.C., LED Driver, TSSOP-28
LINEAR TECH., LT3952EFE#PBF
Optional Electrical Components
1
1
C7
CAP., 0.47μF, X5R, 10V, 10%, 0402
MURATA, GRM155R61A474KE15D
2
1
C8
CAP., ALUM. ELECT.,33μF, 50V, 20%, D8 CASE
PANASONIC, EEHZA1H330XP
3
1
C9
CAP., 0.1μF, X7R, 10V, 10%, 0402
MURATA, GRM155R71A104KA01D
4
0
C10, C12(OPT)
CAP., OPTION, 1206
OPT.
5
0
C11, C13(OPT)
CAP., OPTION, 0402
6
1
D2
DIODE, RECTIFIER, 100V, 1A, SMA
DIODES INC., ES1B-13-F
7
1
FB1
IND., BEAD, CHIP, 100Ω, ±25%, 0805
TDK, MPZ2012S101AT
8
0
Q1(OPT)
XSTR., OPTION, PNP, SOT-23
OPT.
9
1
R6
RES., SENSE, 0.015Ω, 1W, 1%, 1206
PANASONIC, ERJ8BWFR015V
10
1
R7
RES., 499k, 1/16W, 1%, 0402
VISHAY, CRCW0402499KFKEA
11
1
R8
RES., 71.5k, 1/16W, 1% 0402
VISHAY, CRCW040271K5FKED
12
1
R9
RES., 25.5k, 1/16W, 1% 0402
VISHAY, CRCW040225K5FKED
13
0
R10, R11, R15, R16,
R19-R23(OPT)
RES., OPTION, 0402
OPT.
14
3
R12, R13, R14
RES., 100k, 1/16W, 1%, 0402
VISHAY, CRCW0402100KFKED
NIC, NRC04F1003TRF
15
0
R17(OPT)
RES., OPTION, 0603
OPT.
16
1
R18
RES., 0Ω, 1/10W, 0603
VISHAY, CRCW06030000Z0EA
NIC, NRC06ZOTRF
1
7
E1-E7
TEST POINT, TURRET, .094" MTG. HOLE
MILL-MAX, 2501-2-00-80-00-00-07-0
2
8
E8-E15
TEST POINT, TURRET, .064" MTG. HOLE
MILL-MAX, 2308-2-00-80-00-00-07-0
3
1
JP1
CONN., HEADER, 2 × 3, 2mm
Würth Elektronik, 62000621121
4
1
XJP1
SHUNT, 2mm
Würth Elektronik, 60800213421
Hardware
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DEMO MANUAL DC2361A
SCHEMATIC DIAGRAM
dc2361af
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.
7
DEMO MANUAL DC2361A
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
dc2361af
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Linear Technology Corporation
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●
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