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.

temperature range.APPLICATIONS Advanced TVs PDP HDTVs LCD TVs (HDTV ready) LCD/DLP? rear

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 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.

Demonstration circuit 876 is a dual step-up white LED driver with wide dimming range featuring the LT3486. The board is optimized to drive a string of six, eight, or ten white LEDs at 100mA from each of its two outputs with a PVIN input voltage range of 3V to 25V. The maximum LED output voltage must be less than 36V as the overvoltage protection at the output will limit the maximum output voltage to 36V in the case of an open circuit load. The high input voltage range, high-efficiency low-side internal 1.3A NPN power switches, ground-referenced low-voltage current sense resistors, PWM pins for 1000:1 dimming ratio, control pins for brightness adjust, overvoltage protection, shutdown control pin, externally programmable switching frequency, low shutdown current and internal soft-start capacitor make the LT3486 an extremely powerful and versatile LED driving IC for portable applications and displays.

Demonstration Circuit 395A is a Low Noise, Charge Pump White LED Driver featuring the LTC3202. The LTC3202 is a fractional charge pump LED driver that operates from 2.7V to 4.5V (3.3V nominal) and provides up to 125mA of LED current. The demo board includes 6 white LEDs in parallel, supplying approximately 20mA of current per LED.  Controls pins D0 and D1 set the values for the internal 2-bit DAC, which allows LED current to be adjusted for LED brightness control.

Demonstration circuit 1137 is a 20mA Six White LED Driver and OLED driver with Integrated Schottky featuring the LT3498. The LT3498 is a dual output boost converter featuring a 2.3MHz PWM LED driver and a PFM (Pulse Frequency Modulation) OLED driver. The demo board is designed to operate from 3V to 5V, ideal for Li Ion battery powered dual display applications, such as main and sub-displays for cell phones. The demo board offers flexible LED dimming methods. Users can use DC dimming, filtered PWM dimming or direct PWM dimming. The parts functions as a “one-wire” current source from the LED string point of view. The circuit protection clamps LED driver output to 27V (typ) if an open circuit condition occurs. When CTRL2 is higher than 1.5V, the demo board OLED supply output voltage is 16V. It can deliver up to 24mA from a 3V source.

Demonstration circuit 1288 is a Triple Boost or Buck-Boost LED Driver featuring the LT3496EUFD (for evaluating an LT3496 buck mode LED driver, use the demonstration circuit 986). The LT3496 is a triple output DC/DC converter designed to operate as current sources for driving high current LEDs. The board can be configured as either a buck-boost (default) or boost solution. The current for each output is set at 200mA in either mode. The three LEDs are included in the demo board assembly. The operating power input voltage (PVIN) range is 8V to 16V. The buck-boost circuit can tolerate an input voltage up to 40V when the LED string is on the high side. The part shuts down when the overvoltage threshold is reached. For a typical application with 5 LEDs totaling 16V of LED voltage, the circuit will operate until PVIN reaches 22V if the overvoltage protection is set to 38V.

Demonstration circuit 2339A is a high current synchronous step-down LED driver featuring the LT3744. The unique drive stage used on the LT3744 allows the anodes of three LEDs to be connected together for better heat sinking in both the step-down configuration and the inverting buck-boost configuration (shown in a separate demonstration circuit DC1930A). The pros and cons of each configuration can be found in the data sheet.  The DC2339A targets high power LEDs and laser diodes (not included). The 3 LEDs are driven from the same output, but each LED is individually controlled. The input voltage range is 5.5V to 30V.

Demonstration circuit 1187 is an RGB LED Driver and Charge Pump featuring the LTC3212. The LTC3212 is a low noise boost charge pump capable of driving three LEDs at up to 25mA each. The charge pump operates in either 1x or 2x mode, with automatic mode switching. Individual current sources allow each LED to be turned on individually, in combination with the other LEDs, or in white mode using a single wire interface. The demo board input voltage range is 2.7V to 5.5V. White mode optimizes the red, green, and blue current settings to provide the best white color. LED currents are regulated using internal low dropout current sources. Automatic mode switching optimizes efficiency by switching modes only when a dropout is detected.