36V, 2-ch, 1.6A synchronous buck LED driver has I²C dimming

The LT3964 operates with a 4V to 36V input range, and features two independently controlled LED drivers that switch at up to 2 MHz, resulting in a highly integrated, compact solution with small external components.

The LT3964 employs fixed frequency, current mode control and operates as a constant-current and constant-voltage source with accurate current regulation to provide optimal LED lighting in automotive, industrial and architectural lighting applications. Synchronous operation results in efficiencies above 94% with both channels at full current load.

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

The LT3964’s switching frequency is programmable from 200 kHz to 2 MHz or it can be synchronized to an external clock signal. LED driver protection features include open LED and short-circuit LED fault detection, and LED overcurrent and overvoltage detection, all of which can be reported via the I²C interface. Thermal shutdown provides an added layer of protection.

The LT3964EUHE is available in a thermally enhanced 36-lead 5 x 6 mm QFN package. Three temperature grades are available, with operation from –40°C to 125°C (junction) for the extended and industrial grades, and a high temperature grade of –40°C to 150°C. Pricing is from $4.50 (1000).

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