We are using 9 clusters of 3 MP4689A drivers in parallel to drive “flashing” LEDS, 100ms pulses. Additionally we use PWM dimming with 20kHz frequency.
Doing this effects in poor EMC emmition performance. We tried to add a 1nF capacitor in parallel to the LED, which helped. Is there any other measures that could be taken?
Does anyone know about a MP driver suitable for driving the LEDs of each cluster (3 LEDs each) to reduce the number of drivers from 27 to 9?
Hi Roman,
Thank you for posting on the MPS Technical Forum.
What output voltage ripple are you targeting with the 1nF output capacitor? Is the ESR of the capacitor being minimized? Some possible actions to improve EMC performance include:
Decreasing the output voltage ripple as per this equation:
If you haven’t already, consider staggering the enable signals of each cluster on the order of 50-100 µs offsets to limit parallel inductor switching
On a layout level, ensuring a GND connection is closest to the output capacitor (and not the switching paths)
As far as a multi-channel LED driver to reduce the total number of drivers, the closest device for your application would be the MPQ7210-AEC1. The maximum input voltage for the part is 60V, and two channels can be connected in parallel to support up to 4A of output current (or separately 2A per channel). If your input voltage allows, this device may be able to decrease your total number of drivers.
Thanks,
Mason
