Other Parts Discussed in Thread: BQ24040
We went to EMI testing on a new product in the past two days. It uses a BQ24040 linear charger. Ultimately we had issues with the device, though, and failed class B in the 85-95 MHz range. Since this is a linear device, the fact that it could cause so much noise was very surprising to us.
We tried introducing an input filter with an extra capacitor and ferrite bead, but it did not clear up the bad peak.
At this point I'm trying to identify alternatives to the BQ24040 that might better get us through our EMI testing, but if I can get the current chip working it will save a lot of effort.
The current schematic is shown below. We introduced a 330 pF capacitor and a ferrite bead (Wurth 742792651) to turn the input into a pi filter, which as I said was not enough.
The results of the scan are below. The two very large spikes are radio stations and can be dismissed.
