LED driver regulates a string of LEDs up to 34V

The LT3922 is a monolithic, synchronous, step-up DC/DC converter with internal 40V, 2A power switches and an internal PWM generator from Linear Technology.

Fixed frequency peak current mode control regulates current within ±2 per cent for a string of LEDs up to 34V. An integrated PWM generator offers up to 128:1 dimming ratio. For dimming ratios of up to 5,000:1, the converter and an external PWM generator can be used.

The 2.8 to 36V input voltage range can be used for automotive, industrial and architectural lighting. The combination of a Silent Switcher topology and spread spectrum frequency modulation minimises EMI, claims the company. The converter can drive up to 34V of 350mA white LEDs from an automotive input, delivering in excess of 10W.

Efficiencies of 93% can be delivered in the boost topology while switching at 2MHz. There is internal LED short-circuit protection and a frequency adjust pin to allow the user to program the frequency between 200kHz and 2MHz. Other features include frequency synchronization, open and short LED protection and fault indication, programmable UVLO and OVLO, and an accurate LED current monitor

The converter is offered in a thermally enhanced 4.0 x 5.0mm QFN package. Three temperature grades are available, with operation from –40 to 125 degree C (junction) for the extended, industrial grades, and a high temperature grade of –40 to 150 degree C.



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