Part Number:LM5001-Q1
I'm using an LM5001-Q1 to generate 100mA at 30V from an vehicle battery supply (8V to 18V). I used Webench to work out the component values for me, and built a small prototype board using the Webench generated parts. I was expecting to see a continuous switching waveform with a variable duty cycle, depending on load and supply voltage, but what I've got is bursts of switching, with the gap between bursts depending on the supply voltage. Is this what I should be seeing? My colleagues tell me that the board is making a high pitched whistle, which is outside my hearing range(!). The switching frequency is around 500kHz, and the burst rate is about 9kHz. The switching pulses don't have a lot of overshoot or ringing, but at the end of the burst, there is a decaying ringing waveform which lasts for about 150µs, with a frequency close to the switching frequency. If anyone has any ideas, I would be grateful to hear them.