Hello,
We are having EMI issues with LM5145 during specifics circumstances. We have optimized the routing as described in the datasheet and added gate resistors to the transistors as well as snubber circuit between switching node and ground. Radiated emissions look controlled and reasonable during 30-42 V in 24 V out, light load and heavy load. During 20-24 Vin (still with 24 V out setting) we see good results at heavy loads but significant emissions during light load.
Oscilloscope measurements show that there is undesirable ringing at the switch node during light load and low input voltage. When reducing the supply using a power box we see a significant increase in ringing as soon as the supply voltage closes in on output voltage during light load.
What steps can we take to reduce the radiated emissions in this mode except gate resistances and snubbers? It is possible to stop the circuit from switching the external FETs when the supply goes beneath set output?
We currently operate the circuit around 400 kHz, is it very beneficial in terms of EMI to reduce this frequency and use a larger coil?
