From: Sean Breheny <shb7@cornell.edu>
To: Microcontroller discussion list - Public. <piclist@mit.edu>
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Date: Fri, 17 Jan 2020 11:37:04 -0800
Subject: Re: [EE] Measurement noise, signal superimposed on H-Bridge
 operation.
Thread-Topic: [EE] Measurement noise, signal superimposed on H-Bridge
 operation.
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Lots of possibilities:

1) Can we see the whole circuit?
2) Try adding ferrite beads in the gate lead of the mosfets (during turn-on
and turn-off there can be a very high gain which can amplify RF oscillation=
)
3) How well do you bypass the power and ground close to the h-bridge?
4) Why do you want shoot-thru?
5) Consider separate ground and power "islands" for the h-bridge and then
connect them to the rest of the circuit at only one point each (and have
lots of bypass caps sprinkled about the fets, linking the power and gnd
islands)
6) Why does your diagram show a block called h-bridge which is itself
switched by another low-side fet?


On Fri, Jan 17, 2020, 1:38 PM Jason White <whitewaterssoftwareinfo@gmail.co=
m
wrote:

> As a follow up: I have attached a screen capture showing the waveform
> of the noise.
>
> The signal presents itself as 1 cycle of a sine wave at 12.5MHz
> followed by 12 cycles of a sine wave at 62.5MHz on a 100MHZ scope
> using a 25MHz differential probe. Less than 400ns in duration from
> start to finish.
>
> Just writing this out made me think: while I would like to eliminate
> the radiation from my circuit - I may or may not be able to. Perhaps I
> can filter it out of my measurements?
>
> --
> Jason White
> --
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