"Daniel Kelly (AKA Jack)" schreef in bericht news:cko5qp$n34$ snipped-for-privacy@uns-a.ucl.ac.uk...
Most likely the ringing comes from radiation. Too long powerlines that are not properly decoupled or long and/or thin traces in the power circuit. The coil itself also may be a radiation source. You may have to redesign the layout. Keep the traces around chip and coil thick and short. The same for the other components. You may need some shielding or a ground plane. Keep the input lines away from the powersupply.
I see no use for a diode in the power supply input. A decoupling capacitor is absolutely necessary as shown in the example circuit. If that capacitor is good there is no use for a coil. A good decoupling requires a low ESR elco of some tens uF (or larger, depending on the current) parallel to a ceramic capacitor of let's say 10nF.
Main rule: Prevent the disturbing "signal" to escape from the circuit.
petrus bitbyter