IS32LT3965 Synchronous Buck LED Driver

Lumissil's IS32LT3965 high-performance synchronous buck LED driver IC is designed for automotive applications requiring stable LED brightness over a wide operating voltage and temperature range. It is a 1.5 A synchronous switching LED driver with advanced features such as integrated high and low-side FET switches, high-side current sensing, ultra-low 1 μA shutdown current, quick output response, spread spectrum for low EMI, guaranteed -40°C to +150°C operation and housed in a low-profile flip-chip package. These features make it ideal for automotive lighting applications such as dual-brightness daytime running lights (DRL), fog lights, welcome lighting, logo lamps, and motorcycle headlights.

By implementing synchronous rectification, the IS32LT3965 eliminates the need for an external diode and improves the system’s operating efficiency. Replacing the external diode with an integrated FET switch increases a system’s efficiency by minimizing output loss. The IS32LT3965 also implements forced continuous conduction mode (FCCM) to ensure it operates with a fixed frequency under light or full load conditions. Operating at a fixed FCCM frequency of up to 2.2 MHz along with spread spectrum significantly reduces EMI energy peaks. This allows for smaller and lower-cost filter circuits, making it easier to pass Class-5 EMI tests.

The IS32LT3965 is available in an ultra-miniature 3 mm by 4 mm WFCQFN package with wettable flanks that has many benefits, including better EMI performance with reduced switch node ringing. The flip-chip construction results in extremely low parasitic resistance and inductance that minimizes switch node ringing which further reduces EMI. The 14-pin WFCQFN package is designed to provide a direct thermal path from the silicon die to the printed circuit board. The IS32LT3965 has an integrated die temperature monitor and a thermal roll-off function to protect it from any possible effects of high-power dissipation.

The IS32LT3965 1.5 A synchronous buck converter supports a fast transient response over a wide output voltage range without the need for external compensation. A cycle-by-cycle current limit on the high-side FET switch protects the device during overcurrent situations. High-side current sensing makes it possible to drive a remote LED board with only a single wire since the LED cathode is referenced to ground making it possible to use the chassis ground and eliminate the return wire.