TPS5410-Q1: - This regulator is conducting 100MHz noise back to 24V input line.

Thanks for the reply.

Yes, L2 is populated and was added to cut down on the conducted noise back onto the power line. I have tried other values but none seem to effect this high frequency noise on the power line. I will bypass it tomorrow to see the effect.

I will also try a 470nF on the Vin pin.

I will need to look to see if / how the SW node could be smaller.

I also tried a snubber across D13 which seemed to make it worse.  A 150pF across R87 with no effect, and various caps around L2 with no effect.

I did add a 10 Ohm resistor in series with the BOOT cap C54 which helped greatly, but caused chip overheating.

You can try reducing RBOOT value to avoid higher switching loss.

Please let me know how your experiments go.

I jumped across L2 with a slight increase in noise.

I replaced L2 with a 10 uH inductor with no change.

I added a bypass cap on the chip leads from Vin to GND with no change.

I added a capacitor bank of 10uF II .1uF II .01uF  - with no change

I used a .01uF in series with 47 Ohms with only minor change

Nothing is working so far.

Thanks for the experiment.

It sounds so far like the only thing that is helping is slowing down rise time of the HS FET turn-on to limit SW node ringing.

In addition to slow down the turn on with a lower value rboot resistor to avoid inefficiency, you could try and reduce the inductor physical size in case it is coupling back to input wires.

Lastly, make sure your high frequency caps are placed close to the IC to minimize high frequency loop inductance.

I have tried all of the suggestions and nothing is working - I have run out of things to try. When I chose this part I thought that is would be an easy solution.

Does TI offer any other part in the same 8SOIC package and pin-out? Are there other automotive rated parts with low size, 8SOIC package that would not have these noise issues?

The board redesign and retesting is really going to cause great problems.