The ALT80802 is a high-frequency switching regulator that provides constant output current to drive high-power LEDs. It integrates a power MOSFET for step-down or inverting buck boost conversion. The wide input range of 3.8 to 50 V makes the ALT80802 suitable for a wide range of lighting applications, including those in an automotive input environment. The device rating also enables a simple solution for driving 3 to 4 WLEDs in buck boost configuration—a very common application requirement for automotive lighting applications.
The ALT80802 is designed to aid in EMC/EMI design by frequency dithering, soft freewheel diode turn-off, and well controlled switch node slew rates. A programmable oscillator allows the ALT80802 to switch outside EMI-sensitive frequency bands such as the AM band.
With current-mode control and simple external compensation, the ALT80802 can achieve fast transient response. The control loop of the ALT80802 is designed for PWM dimming operation to achieve low dimming on-time and low turn-on overshoot. In buck-boost operation, the ALT80802 reduces the current overshoot normally caused by right half plane zero effect during a PWM diming turn-off transient. Extensive protection features of the ALT80802 include pulse-by pulse current limit, hiccup mode short-circuit protection, open/ short freewheeling diode protection, BOOT open/short voltage protection, VIN under voltage lockout, and thermal shutdown. Also, it includes internal clamp to prevent output voltage runaway if output LED string is opened in buck-boost operation.
The ALT80802 is available in a small 10 pin DFN package with thermal pad and wettable flank (automotive qualified).