Tool/software:
Hi,
I wanted to get some advice regarding connecting the chassis ground of a metal enclosure that contains the PCB of PMP21611. Normally, taking into account ESD and EMI considerations, I would make a low inductance connection of the chassis ground to the signal ground. However, in the case of the PMP21611, there is the common-mode choke that (at least for me) makes things a bit confusing, because of the VBATT- at the input and the GND at the output of it and because chassis ground is essentially the same as VBATT- (at least in our case).
The extra complication that I have in my case is that I'm using this circuit to supply a wireless transceiver with an antenna that is connected to the board via a UFL to SMA cable attached on the enclosure. Therefore, the ground on the SMA connector (which is the signal ground) is connected via the cable to the enclosure (chassis ground). But the enclosure is at the same potential as the "-" of the power in. Essentially, what I'm doing is that I connect VBAT- with GND. I suppose there no meaning in doing that, since then the choke's purpose is diminished or nullified. I've actually also observed failures (perhaps due to noise) in some cases when the connection I described above is there.
I guess what I'm trying to understand is this. If I want to keep the choke (which I think it's a good idea to do), is there a way to still keep the metal enclosure or should I better switch to one with non-conductive material (or maybe isolate the SMA connector from the enclosure)?