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| Ferrite bead/ Capacitor filter causes ringing in output? |
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| Siwastaja:
One thing you need to understand is the timescale of your measured peaks (~100us). The 100n let alone 10n caps can't do anything on this timescale. They are useful in your filter if you have an EMI issue in tens-hundreds of MHz range. Local regulation using a fast regulator is the key. If you look at the typical transient response curves of your TPS62175, it should react in a few µs, even in pulse-skipping power save mode. And, if you are indeed measuring stable output voltage from the regulator, but have dips at the IC power pins, the problem has to be between the regulator and the IC. Let me suggest: the filter is the problem. Possibly too much DC resistance, even! Try connecting the load directly to the regulator output, with a few inches of wire max, and see what happens? |
| Sjoertdb:
Thanks for the input! I'll try adding a regulator with a LE33 from ST. This one has a drop of 200 mV. I'll try to remove all the possible dc resistances. I'll send an update later. Thanks! Your information is very valuable to me! :-+ |
| Sjoertdb:
I've tried tying an LDO to the 3V3 output and the 5V output. The one on the left is the output of the LE33 when 3V3 is used as input, (probably LDO stops regulating by now) The one on the right is an LDO added to 5V, now the issue is completely gone. |
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