This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

LM5118 noise on Vout

Other Parts Discussed in Thread: LM5118, LM3151, TPS56121


We used LM5118 in order to provide power supply for an embedded board.

The LM5118 is designed to provide Vout = 10 to 15V - 4A : Vin = 10 to 30V

We adjust Vout with Rfb1 and Rfb2 with a numeric potentiometer.
We adjust the Vout voltage in order to do loading of 12V lead acid battery.

The LM5118 is the primary power supply, in cascade we have a 5V-6.5A power supply based on TPS56121 and a 3.3V-5A power supply based on LM3151.

Problem :
As you can see on oscilloscope graph, with have lot of noise and ripple on Vout and this perturbation are the same on the other power supply level (5V and 3.3V).

We have mesured noise until 10V peak to peak with the scope meter on the Vout continued voltage.

Channel 1 : mesure between inductor (L21) and diodes (D11/D16)
Channel 2 : mesure on Vout (mesures are in AC mode)

This noise disrupt all of our electronic board particulary our display.

We have try to do FFT on the noise and the primary ray is around 100MHz

Have you some ideas in order to reduce or solve this problem.

Best regard