Isolated Secondary Side 6-CH LED Driver with Optocoupler Driver

The RT8464 is an isolated secondary side 6-CH LED driver that delivers well matched LED current to each channel of LED strings. A built-in optocoupler driver supports the transformer primary side control circuit to regulate the LED current. The LED current is linearly controlled by a high gain amplifier that drives the optocoupler to control the primary side, thus making the conventional secondary DC/DC PWM switching stage unnecessary. The RT8464 selects and regulates the LED strings with the highest voltage, hence it allows voltage mismatches between LED strings. The RT8464 automatically detects and disconnects any unconnected and/or broken strings during operation from the PWM loop to prevent V_OUT from over voltage.

The LED currents on all channels can be simply programmed with a resistor on each channel. Three convenient dimming methods are provided : 1. Analog dimming is linearly controlled by an external voltage; 2. True digitally controlled PWM dimming controls duty cycle of LED current; 3. PWM dimming signal can also be easily filtered into analog dimming signal for noise-free PWM dimming by the low pass filter with an external capacitor at ACTL pin. Other protecting features include output over voltage protection and thermal shutdown.

The RT8464 is available in the SOP-28 package.