Demo circuit DC1274A features the LTM8040 36V, 1A step-down constant current μModule® LED driver. The demonstration circuit is designed to drive a single LED or string of LEDs at up to 1A from a wide input voltage range of 4V to 36V. The maximum LED string voltage is 13V and the minimum voltage varies depending upon the BIAS pin supply arrangement.

Demonstration circuit 2176A features the LT3909, a 2-string × 50mA, 2MHz step-up LED driver with ±1.8% current matching. The LT3909 precisely regulates two LED strings for equal current, supports LED dimming that reduces brightness down to a 1/40,000 ratio, protects against faults and also reports faults. The LT3909 consists of a step-up converter with a fixed 2MHz switching frequency and current sources for the LED strings. The maximum current in each LED string is 40mA. The ISET resistor can be changed to 20.0kΩ to program the string current to 50mA – see the data sheet for an application example with 50mA string current. Voltage feedback resistors optimize operation for LEDs that are 35V maximum.

Demonstration circuit 976 is a Quadruple High Power LED Driver in Buck Mode featuring the LT3476EUHF. The LT3476 is a quad output, multitopology DC/DC converter designed to operate as a current source for driving high current LEDs. Each of the four regulators on the demo circuit is independently operated. The VIN power supply for the IC ranges from 2.8V to 16V. The PVIN power supply for the buck regulators ranges up to 33V. On the demo circuit, the default current for each output channel is 350mA but it can be adjusted up to 1.05A via resistor dividers at the VADJ pins. The output current should not exceed the rated current of the LEDs used. If 1W LEDs, such as the Lumileds Luxeon LEDs, are used, 350mA current is the maximum. 1A output current is reserved for 3W LEDs, such as Luxeon III. The input voltage is limited by the CAP pin overvoltage protection threshold. As a result, each channel of the demo circuit can drive up to 27V total LED voltage.

Demonstration circuit 1470 is a High Current Synchronous Step-Down LED Driver with Three-State Control featuring the LT3743EUFD. The demo board is optimized for 20A output from a 12V input. Being an LED driver, the output current is regulated until the output voltage reaches a programmed voltage limit. The voltage limit on this demo board is set to around 6V by resistors R5 and R6. The 6V is chosen because of the 6.3V voltage rating of the output capacitors. The ideal load to be used with this demo board is a single LED, such as PT120 from Luminus Devices. The input voltage range of the LT3743 is 6V to 36V; however, the demo board utilizes 30V MOSFETs to demonstrate best efficiency, so the maximum recommended input voltage is 24V for the demo board.

Demonstration circuit 2686A is a 1.3A 8-switch matrix LED dimmer system with an I2C to CAN-physical transceiver featuring the LT3967 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: Connect directly to a Linduino One demonstration circuit with a QuikEval™ ribbon cable. Connect using the LT3960 break-off board to connect 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 circuits 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 I2C slave address as well as the default start-up state. The default configuration for DC2686A sets the I2C address as 0000 with all LEDs off. See the LT3967 data sheet for details. The LT3960 I2C to CAN-Physical transceiver is used to send and receive I2C data through harsh or noisy environments 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 conjunction with the 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.

Demonstration Circuit 366A is a low noise constant frequency regulated charge pump featuring the 100mA output current LTC3200. The demo board accepts a 2.7V to 4.5V input voltage and drives six white LEDs in parallel, resulting in 16.6mA per LED. Ballast resistors are employed to provide more uniform light intensity fromr the paralleled LEDs.

DC1436A is a 16-Channel High Voltage Boost LED Driver featuring the LT3754. The LT3754 drives up to 50mA per string and has a maximum LED string voltage of 45V. The VIN terminal is powered from an 8V to 14V input supply and is distinct from the 24V PVIN supply (20V to 28V) for best thermal performance. Overvoltage protection is set at 55V in case the LEDs are removed from the circuit. If the LEDs are opened, the FAULT terminal output flag goes low and reports the fault condition. If one or more of the 16 LED channels is not used, its LED pin or terminal should be tied to VOUT (LED+) to disable it. Multiple channels can be tied in parallel by tying their LED1-LED16 pins together.

Demonstration circuit 1327B is a 4-Channel 80mA LED Driver with +/-1.5% Current Matching featuring the LT3599. The LT3599 is a step-up DC/DC converter designed to drive up to 4-strings of LEDs at up to 120mA per string, and with an output voltage up to 44V. The LED strings are connected to internal current sources where the current level is set with an external resistor. Each string can have up to 10 white LEDs. Paralleling of strings is allowed. The LT3599 runs from a 3.1V to 5.5V power supply, and the step-up converter is powered from an 8V to 16 voltage supply, though higher voltages up to 40V may be acceptable depending on the circuit requirements.

DC1542A: Demo Board for LT3596 60V Step-Down LED Driver.

DC1573A is an 8-Channel High Voltage Boost LED Driver featuring the LT3760. The LT3760 drives up to 100mA per string and has a maximum LED string voltage of 45V. The VIN terminal is powered from an 10V to 14V input supply and is distinct from the 24V PVIN supply (20V to 28V) for best thermal performance. Overvoltage protection is set at 55V in case the LEDs are removed from the circuit. If the LEDs are opened, the FAULT terminal output flag goes low and reports the fault condition.  If one or more of the 8 LED channels is not used, its LED pin or terminal should be tied to VOUT (LED+) to disable it. Multiple channels can be tied in parallel by tying their LED1-LED8 pins together.