Linear's latest monolithic synchronous step-up Silent Switcher LED driver dims smoothly



The LT3922 monolithic, synchronous, step-up DC/DC converter

The LT3922 is a monolithic, synchronous, step-up DC/DC converter with internal 40V, 2A power switches and an internal PWM generator. Its fixed frequency peak current mode control accurately regulates current within ±2% for a string of LEDs up to 34V. Its integrated PWM generator offers up to 128:1 dimming ratio. If dimming ratios of up to 5,000:1 are required, the LT3922 and an external PWM generator can accommodate these applications. The LT3922’s 2.8V to 36V input voltage range is ideal for a wide range of applications, including automotive, industrial and architectural lighting. The combination of a Silent Switcher topology and spread spectrum frequency modulation minimizes EMI concerns. The LT3922 can drive up to 34V of 350mA white LEDs from an automotive input, delivering in excess of 10 watts.

The LT3922 incorporates a high side current sense, enabling its use in boost, buck mode or boost-buck topologies. It can deliver efficiencies of 93% in the boost topology while switching at 2MHz, offering a tiny and compact solution footprint. Internal LED short-circuit protection enables added reliability. A frequency adjust pin permits the user to program the frequency between 200kHz and 2MHz. Combined with a thermally enhanced 4mm x 5mm QFN package, the LT3922 offers a very compact high power LED driver solution. Other features include frequency synchronization, open and short LED protection and fault indication, programmable UVLO and OVLO, and an accurate LED current monitor.

The LT3922EUFD is available in a thermally enhanced 28-lead 4mm x 5mm QFN package. Three temperature grades are available, with operation from –40°C to 125°C (junction) for the extended, industrial grades, and a high temperature grade of –40°C to 150°C. Pricing starts at $3.95 each in 1,000-piece quantities and all versions are available from stock. 


Linear Technology