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Power Electronics Europe News
Synchronous buck LED driver simplifies dimming control
The LT39664 has internal 40V, 1.6A power switches and an I²C interface. It operates over a wide 4.0 to 36V input range, and has two independently controlled LED drivers that switch at up to 2MHz. According to the company, this results in an integrated, compact solution with small external components.

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

The 400kHz I²C interface can simplify digital PWM dimming as a PWM signal from a microcontroller to the LED driver is no longer necessary. Internal registers are programmed with the desired dimming duty cycle, which is synchronised to the internal clock to provide dimming ratios up to 8192:1 and eliminate beat frequencies caused when the PWM signal and the internal oscillator are not synchronised.


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 analogue dimming are also provided.

The switching frequency is programmable from 200kHz to 2MHz or it can be synchronised to an external clock signal. LED driver protection features include open LED and short-circuit LED fault detection, and LED over-current and over-voltage 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 5.0 x 6.0mm QFN package. Three temperature grades are available, operating from -40 to 125°C (junction) for the extended and industrial grades, and -40 to 150°C for a high temperature version.

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