Dimmer chip simplifies complex LED matrix designs

December 09, 2015 // By Christoph Hammerschmidt
The LT3965 is a LED bypass switching device that enables independent dimming and diagnostics of eight individual LEDs or LED segments like those in matrix headlamps for cars. Working in conjunction with a LED driver circuit configured as a current source, the chip features eight individually controlled floating 17V/330mΩ NMOS switches . Using these internal power switches and an integrated I2C serial interface, individual LEDs within the string can be turned on or off, or they can be PWM dimmed to offer unique patterns within the LED matrix.

Besides automotive matrix LED headlights, typical applications for the LT3965include industrial lighting and large LED display lighting. The I2C serial interface enables digital programming with 256:1 dimming ratios with or without the 11-bit resolution fade transition between the dimming states. Each switch can control and monitor a single LED or a segment of up to 16V of series-connected LEDs.

The LT3965’s 8V to 60V input voltage range can accommodate a wide range of LED drivers commonly used in automotive and industrial applications. For larger LED matrix applications, multiple LT3965s (up to 16) can use a common I2C bus.

The LT3965’s eight switches can be connected in parallel and/or in series to bypass current around one or more LEDs in a string. When multiple LT3965s are used, the I2C serial interface enables communication between the master microcontroller and one or more LT3965s configured as slaves. The LT3965 provides an internal clock generator and also supports an external clock source for PWM dimming.

Additionally, each channel of the LT3965 offers both open LED and shorted LED fault reporting and protection. It is offered in a 28-lead TSSOP thermally enhanced package, ensuring a compact solution footprint for matrix dimming applications.

For more information, visit www.linear.com/product/LT3965.