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should connector ground be connected to circuit ground?

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fala

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hi, I have a question about philips application note ESG89001(https://www.web-ee.com/primers/files/u89001.pdf). I think I couldn't understand one point. on page 10 it says: "it may be necessary to make a separation between
the reference-strip near to the connectors and the groundplane, groundgrid or reference of the circuitry on the PCB. This groundstrip shall, if applicable, be connected to the metal cover of the product. From this separate
groundstrip, only high impedances; inductors,resistors, reed relays and opto-couplers are allowed in between these two grounds." what it means? does it mean that connector ground should not be connected directly to circuit ground? figure 12 on page 11 just adds to my confusion these two grounds(connector and circuit) seems completely isolated for DC. I didn't understand what // in this figure means. does it mean that metal cover should not be connected to circuit ground at DC?
can someone please explain it to me ? thanks in advance.

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IanP

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.. it may be necessary to make a separation between the reference-strip near to the connectors and the groundplane, groundgrid or reference of the circuitry on the PCB ..

This describes a very specific situation where you have connectors providing interconnections for other external panels through a PCB, which, from its point of view, has almost nothing to do with "the other blocks/panel" ..
It is obvious then that you want to keep interference between these blocks as low as possible, and an effective way of doing so is to separate their grounds/shields by total isolation (optical) or high impedance link (choke) ..

The "//" means, for example, that you can connect an inductor (RF choke) between these two grounds, and by doing so you will provide a dc reference, but in the same time, with decoupling caps at both sides, you will practically "shut down" any inteference from one side to the other and the opposite way around ..

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IanP
 

    fala

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fala

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thanks IanP, you are really helpful. this concept has many significances for me because till now I used to connect sheild of I/O cables and also metal cover directly to my analog ground.

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