1
DEMO MANUAL DC2686A
Rev. 0
DESCRIPTION
LT3967/LT3960
1.3A 8-Switch Matrix LED Dimmer with I2C
to CAN-Physical Layer Transceiver
Demonstration circuit 2686A is a 1.3A 8-switch matrix LED
dimmer system with an I2C to CAN-physical transceiver
featuring the LT
®
3967 and LT3960. This demonstration
circuit connects directly to a LED string and LED driver
demonstration circuit to allow for independent dimming
control of up to 8 channels of LEDs. A Linduino
®
One
demonstration circuit is used to interface with the board
and can connect in one of two different ways:
1. Connect directly to a Linduino One demonstration
circuit with a QuikEval™ ribbon cable.
2. Connect using the LT3960 break-off board to con-
nect to the I2C master device, but pass data over two
twisted pair lines to the LT3960 on the main PCB.
The LT3967 matrix dimmer features 8 individually con-
trolled 1.3A rated floating NMOS switch channels and can
support up to 56V of LEDs per device. The channels of
the LT3967 can be configured for series connections, or
non-series connections. Additional DC2686A demo cir-
cuits can be connected in series for higher number of
LEDs, or in parallel to allow for higher current operation.
Resistors are used to configure both the I
2
C slave address
as well as the default start-up state. The default configu-
ration for DC2686A sets the I2C address as 0000 with all
LEDs off. See the LT3967 data sheet for details.
All registered trademarks and trademarks are the property of their respective owners.
The LT3960 I2C to CAN-Physical transceiver is used to
send and receive I2C data through harsh or noisy envi-
ronments at up to 400kb/s using the CAN-Physical layer
for differential signaling over twisted pair connections.
Both SDA and SCL data lines are converted to differential
signals and are shared between devices connected to the
bus. This allows for physical separation of the I2C source
with the LT3960 transceiver board and the LT3967 main
PCB along with the LED driver.
This demo circuit is designed to be easily configured and
interfaced with a compatible low output capacitance LED
driver and LED string. It can easily be directly attached
to a buck LED driver or a floating buck-mode LED driver.
More sophisticated setups with series matrix dimmers
for higher number of LEDs such as 12 or 16 is possible.
Please consult factory applications for details or look for
more details on analog.com.
The LT3967 and LT3960 data sheets give complete
description of the parts, their operation and applications
information. The data sheets must be read in conjunc-
tion with this demo manual for demonstration circuit
DC2686A. The LT3967EFE is assembled in a thermally
enhanced 28-lead TSSOP package. The LT3960EMSE is
assembled in a 10-lead MSOP package.
Design files for this circuit board are available.
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DEMO MANUAL DC2686A
Rev. 0
PARAMETER CONDITION MIN TYP MAX UNIT
Input Voltage LT3967, Operating
LT3960, Operating
8
4.5
5
60
5.5
V
V
LED Voltage LT3967, Operating 56 V
LED Current LT3967, Operating 1.3 A
LT3967 ENH Threshold Falling Voltage (VIN – ENH) R1 = 10k, R2 = 49.9k 1.10 1.22 1.34 V
LT3960 EN/MODE Voltage Master Mode
Slave Mode
Low-Power Shutdown Mode
2
0.7
0
5
2
0.7
V
V
V
Ext LDO Output Voltage R22 = 392k, R23 = 127k 5 V
Ext CLK Frequency R13 = 57.6k 350 kHz
LT3967 PWM Dimming Frequency Ext CLK to RTSYNC 170 Hz
LT3967, LT3960 I2C CLK Frequency 400 kHz
LT3967 POR Initial Switch State RADRR[4:1] = 0Ω LED Off
In order to properly function, DC2686A must be interfaced
with a low output capacitance Buck LED driver or floating
buck-mode LED driver. The input power supply to both
LED driver and DC2686A must be set to at least 6V higher
than each LT3967 SRC channel source voltage. This demo
manual highlights interfacing DC2686A with a buck LED
driver. For buck mode connections, refer to the LT3967
data sheet.
DC2686A works with a Linduino microcontroller board
(DC2026C) and can be connected to a PC via USB. This
allows DC2686A to be controlled via serial port interface
in Arduino IDE. Refer to the DC2026C demo manual for
detailed instructions on installing and configuring the nec-
essary software and libraries.
1. Launch Arduino IDE.
2. Connect Linduino to computer via USB.
3. Download the Linduino code and library files from the
DC2686A web page
4. Upload the code to the connected Linduino
democircuit.
5. With input power off, connect the input power supply
from LED Driver to VIN and GND of DC2686A.
6. Connect LED
+
and LED
–
from LED driver to DC2686A
LED+ and LED– terminals.
7. Connect 8 LEDs as shown in Figure1 and Figure2.
8. Connect Linduino to DC2686A using one of the two
methods shown in Figure1 and Figure2.
9. Open up the serial monitor inside Arduino IDE.
10. Turn on input power supply.
11. Use command line interface in serial monitor to con-
trol and monitor LEDs.
QUICK START PROCEDURE
PERFORMANCE SUMMARY
Specifications are at TA = 25°C
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DEMO MANUAL DC2686A
Rev. 0
Figure1. Quick-Start Procedure Setup Drawing for DC2686A (without LT3960)
Figure2. Quick Start Procedure Setup Drawing for DC2686A (with LT3960)
QUICK START PROCEDURE
*SNAP OFF SMALL BOARD
FROM THE MAIN BOARD
TO SET UP VIA LT3960
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DEMO MANUAL DC2686A
Rev. 0
SETUP DIFFERENCES BETWEEN BUCK VS BUCK-MODE
When using DC2686A with a buck LED driver, connect the
VIN of the buck LED driver directly to VIN of LT3967, and
ensure that VIN is 6V higher than channel source voltages
on the LT3967. When interfacing with a floating buck-
mode LED driver, a charge pump is necessary to create
the needed 6V headroom from VIN to VSRC. Please ref-
erence LT3967 data sheet for details on how to properly
implement this.
SETTING THE ADDRESS AND POR DEFAULT
SWITCHSTATE
Both the I2C address and power-on-reset (POR) default
switch state are configured by placing resistors between
the ADDR pins. Connecting the ADDR pins either VDD or
GND defines the unique I
2
C address. Using a resistor value
less than 5k to set the address configures the LT3967
to start-up with the LEDs off, and using a resistor value
greater than 50k configures the LEDs to be on. Refer to
the LT3967 data sheet for detailed explanation on setting
the default POR settings and I2C address.
SETTING THE PWM DIMMING FREQUENCY
Dimming frequency for the LT3967 can be configured
either by the internal oscillator or an external clock source.
The LT3967’s internal oscillator frequency is set by con-
necting a resistor from the RTSYNC pin to GND. Refer to
the LT3967 data sheet for guidance on sizing this resistor
for the desired dimming frequency.
An external clock source capable of sink 500µA at 0.4V
can be used to override the internal oscillator. If either
the internal oscillator or external clock source become
slower than 100kHz, then the IC will switch to a 100kHz
internal standby clock. The PWM dimming frequency is
derived using clock division of the RTSYNC signal, diving
down by2048. DC2686A is equipped with an external
clock source (LTC6900CS5) that can be powered from the
5V rail of either the onboard LDO or a connected Linduino.
UTILIZING LT3960 FOR SERIAL COMMUNICATION
The LT3960 can be used to communicate with the
LT3967 over longer distances and/or in noisy environ-
ments. DC2686A has two LT3960 ICs, one local to the
LT3967IC, and another on a snap-off board that plugs
directly into the QuikEval header of the Linduino demo
circuit (DC2026C).
The LT3960 on the snap-off board is powered by a
Linduino when connected via QuikEval header. The EN/
MODE pin is tied to the drain of a MOSFET that can be
controlled by a Linduino. The MOSFET allows configu-
ration of IC to be set to master mode, slave, or power
off. The LT3960 on the main board can be powered by
the on-board LDO. EN/MODE pin is not connected, con-
figuring this device in slave mode. Twisted pair connec-
tions should be made between the differential pins of the
LT3960 using the terminal blocks to connect.
PROGRAMMING THE NUMBER OF CHANNELS
A single LT3967 can control up to 8 individual chan-
nels. For any unused channels, connect the associated
DRN pins to V
DD
with 100k resistor and the SRC pins
to GND. This ensures proper fault monitoring for the
unusedchannels.
LEDs can be driven in series by adding 0Ω resistors to
R6, R7, R10, R11, R12, R14, R15, which connects adja-
cent DRN and SRC channels at the J2 and J4 connectors.
Channels can also be separated for individual LEDs control
with non-serial LED string connections. DC2686A is con-
figured for 8-channel operation but has resistor options
that allow for easy reconfiguring to allow for as low as
6LEDs. Solder a 0Ω resistor to R16, R18, and 100k to
R20, R21 to defeat the lower 2 channels of the LT3967.
CONFIGURING THE ARDUINO COM TERMINAL
For operation of the command line interface, parameters
of the terminal window must be set properly. 115200
Baud, No line ending, and Clear output should be selected.
See Figure3 for details.
BOARD OPTIONS
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DEMO MANUAL DC2686A
Rev. 0
Figure3. Arduino COM Terminal Window; Selectable Options Menu
BOARD OPTIONS
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DEMO MANUAL DC2686A
Rev. 0
Figure4. Two Series-Connected LT3967 ICs
ADDR1
ADDR2
ADDR3
ADDR4
LT3967
ENH
ALERT
SCL
SDA
RTSLK
VDD
ALERT
SCL
SDA
49.9k
LED+
CIN3
1µF
100V
D2
VIN
VIN
GND
WDI
D6
D8
D7
S7
S8
S6
D5
S5
D4
S4
D3
S3
D2
S2
D1
S1
LED–0.1µF
+5V
+5V
ADDR1
ADDR2
ADDR3
ADDR4
LT3967
ENH
ALERT
SCL
SDA
RTSLK
VDD
ALERT
SCL
SDA
10k
49.9k
LED+
CIN2
1µF
100V
D1
VIN
GND
WDI
D6
D8
D7
S7
S8
S6
D5
S5
D4
S4
D3
S3
D2
S2
D1
S1
0.1µF
+5V
+5V
LED+
EXTERNAL
CLOCK
SOURCE
+5V
1k
1k
1k
1k
DC2786A F04
BOARD OPTIONS
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DEMO MANUAL DC2686A
Rev. 0
TEST RESULTS
Figure5. Thermal Capture of DC2686A at 50VIN, 8 Channels Shorted Through IC at 1.3A. LED+ = 1.2V, LED− = 0V
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DEMO MANUAL DC2686A
Rev. 0
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
Required Electrical Components for LT3967 Matrix Dimmer
1 1 C1 CAP., 1µF, X7S, 100V, 10%, 0805, AEC-Q200,
NOSUBS.ALLOWED
MURATA, GCM21BC72A105KE36L
2 1 C4 CAP., 0.1µF, X7R, 10V, 10%, 0402, AEC-Q200 MURATA, GCM155R71A104KA55D
3 1 D1 DIODE, SCHOTTKY, 60V, 1A, SOD-123F, AEC-Q101 NEXPERIA, PMEG6010CEH, 115
4 1 R1 RES., 10k, 1%, 1/10W, 0603, AEC-Q200 VISHAY, CRCW060310K0FKEA
5 1 R2 RES., 49.9k, 1%, 1/10W, 0603, AEC-Q200 PANASONIC, ERJ3EKF4992V
6 1 U1 IC, 8-SWITCH MATRIX LED DIMMER, TSSOP-28, 1.3A ANALOG DEVICES., LT3967EFE#PBF
Optional Electrical Components for LT3967 Matrix Dimmer
7 1 C5 CAP., 0.1µF, X7R, 16V, 10%, 0603, AEC-Q200 MURATA, GCM188R71C104KA37D
8 6 RC1, R3, R40, R41, R42, R43 RES., 0Ω, 1/10W, 0603, AEC-Q200 VISHAY, CRCW06030000Z0EA
9 1 R4 RES., 10k, 1%, 1/16W, 0402, AEC-Q200 VISHAY, CRCW040210K0FKED
10 0 R6, R7, R10, R11, R12, R14,
R15, R16, R18, R19, R20,
R21, R44, R45, R46, R47
RES., OPTION, 0603
11 1 R13 RES., 57.6k, 1%, 1/10W, 0603, AEC-Q200 PANASONIC, ERJ3EKF5762V
12 1 R17 RES., 121k, 1%, 1/10W, 0603, AEC-Q200 VISHAY, CRCW0603121KFKEA
13 1 R39 RES., 22k, 1%, 1/10W, 0603, AEC-Q200 VISHAY, CRCW060322K0FKEA
14 1 U2 OSCILLATOR, 1kHz to 20MHz, 5k AND/OR 10pF,
±40ppm,TSOT23-5, RESISTOR SET OSC.
ANALOG DEVICES, LTC6900CS5#PBF
Required Electrical Components for LT3960 I2C CAN
15 2 C9, C15 CAP., 2.2µF, X7S, 10V, 10%, 0603, AEC-Q200 TDK, CGA3E3X7S1A225K080AB
16 2 C10, C13 CAP., 1µF, X7R, 25V, 10%, 0603, AEC-Q200 MURATA, GCM188R71E105KA64D
17 4 C11, C12, C14, C16 CAP., 4700pF, X7R, 25V, 10%, 0402, AEC-Q200 YAGEO, AC0402KRX7R8BB472
18 1 Q1 XSTR., MOSFET, N-CH, 60V, 210mA, SOT-23, AEC-Q101 DIODES INC.2N7002Q-7-F
19 4 R25, R26, R33, R34 RES., 4.99k, 1%, 1/10W, 0603, AEC-Q200 VISHAY, CRCW06034K99FKEA
20 8 R27, R28, R29, R30, R31,
R32, R35, R36
RES., 60.4Ω, 1%, 1/8W, 0805, AEC-Q200 VISHAY, CRCW080560R4FKEA
21 1 R38 RES., 1k, 5%, 1/10W, 0603, AEC-Q200 VISHAY, CRCW06031K00JNEA
22 2 U4, U5 IC, 12C TO DUAL CAN TRANSCEIVER, MSOP-10 ANALOG DEVICES, LT3960EMSE#PBF
Optional Electrical Components for LT3960 I2C CAN
23 1 R37 RES., 0Ω, 1/10W, 0603, AEC-Q200 VISHAY, CRCW06030000Z0EB
Components for Optional 5V Source
24 1 C7 CAP., 0.47µF, X7R, 16V, 10%, 0603, AEC-Q200 MURATA, GCM188R71C474KA55D
25 1 C8 CAP., 1µF, X7R, 25V, 10%, 0603, AEC-Q200 MURATA, GCM188R71E105KA64D
26 0 R5 RES., OPTION, 0805
27 1 R22 RES., 392k, 1%, 1/10W, 0603, AEC-Q200 VISHAY, CRCW0603392KFKEA
28 1 R23 RES., 127k, 1%, 1/10W, 0603, AEC-Q200 VISHAY, CRCW0603127KFKEA
29 1 R24 RES., 0Ω, 1/10W, 0603, AEC-Q200 VISHAY, CRCW06030000Z0EA
30 1 U3 IC, LDO MICROPOWER LINEAR REG., SOT23-5, 20mA,
3VTO 80V
ANALOG DEVICES, LT3014IS5#PBF
PARTS LIST
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DEMO MANUAL DC2686A
Rev. 0
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
Hardware
31 4 E1, E2, E3, E4 TEST POINT, TURRET, 0.094" MTG. HOLE, PCB 0.062" THK MILL-MAX, 2501-2-00-80-00-00-07-0
32 3 E5, E6, E7 TEST POINT, TURRET, 0.064" MTG. HOLE, PCB 0.062" THK MILL-MAX, 2308-2-00-80-00-00-07-0
33 1 J1 CONN., HDR, SHROUDED, MALE, 2×7, 2mm, VERT, ST, THT MOLEX, 87831-1420
34 2 J2, J4 CONN., HDR, MALE, 1×10, 2.54mm, VERT, ST, THT SAMTEC, TSW-110-07-L-S
35 2 J3, J6 CONN., TERM BLOCK, 5 POS, 2.54mm, ST, THT,
SIDEENTRY, GREEN
ON-SHORE TECHNOLOGY, OSTVN05A150
36 1 J5 CONN., SOCKET STRIP, RCPT, FEMALE, 2×7, 2mm,
VERT,ST, THT
MOLEX, 0791077006
PARTS LIST
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DEMO MANUAL DC2686A
Rev. 0
SCHEMATIC DIAGRAM
11
DEMO MANUAL DC2686A
Rev. 0
Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog
Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications
subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
SCHEMATIC DIAGRAM
12
DEMO MANUAL DC2686A
Rev. 0
ANALOG DEVICES, INC. 2020
09/20
www.analog.com
ESD Caution
ESD (electrostatic discharge) sensitive device. Charged devices and circuit boards can discharge without detection. Although this product features patented or proprietary protection
circuitry, damage may occur on devices subjected to high energy ESD. Therefore, proper ESD precautions should be taken to avoid performance degradation or loss of functionality.
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