LED driver simplifies dimming control

December 03, 2017

A dual-channel step-down LED driver, the LT3964 from Linear Technology packs 40 V, 1.6 A power switches and an I2C interface for dimming control. Operating over an input voltage range of 4 V to 36 V, the driver integrates two independently controlled LED drivers that switch at up to 2 MHz. Synchronous operation results in efficiencies above 94% with both channels at full current load.

The part’s 400 kHz I2C interface greatly simplifies digital PWM dimming. A PWM signal from a microcontroller to the LED driver is not necessary. Rather, internal registers are programmed with the desired dimming duty cycle, which is synchronized to the internal clock. This provides dimming ratios of up to 8192:1 and eliminates beat frequencies caused when the PWM signal and the internal oscillator are not synchronized. Alternatively, with analog dimming, an I2C settable 8-bit scale factor sets the control voltage-to-LED current ratio. 1000:1 external PWM dimming and 10:1 analog dimming are also supported.

LED driver protection features include open LED, short-circuit LED, LED overcurrent, and LED overvoltage detection, all of which are reported via the I2C interface. Thermal protection provides an added layer of protection.

The LT3964 comes in a 36-lead, 5×6-mm QFN package and in three temperature grades. Prices for the driver start at $4.50 each in lots of 1000 units. Samples and production quantities are available now.

LT3964 product page

Linear Technology, www.linear.com

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