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I am designing a little mezzanine PCB that uses Hirose DF12 connectors to connect to the motherboard.
Four different voltages are delivered to this PCB: ±10v, 3.3v, 48v (and ground). They go through one of the DF12 connectors.
Which of these two ways is the preferred way to lay out the power and ground connections on the connector?
First way: Each power has its own ground.
Second way: Single set of ground shared by all power.
I would keep grounds separate especially if you have sensitive analog and ONLY tie them at the power supply, or at least at only one place if not at the power supply.
Also, I'd physically separate powers in your connector by one pin position. For example on #2, put a space between 3.3V and +10V (pins 36 and 37).
I usually lay out my connectors based on where the circuit components are physically located relative to the connector. Pay attention to return currents and try to keep them from crossing each other, if you've tied all the grounds together on your mezzanine. With segregated grounds you mitigate this but then have to make sure your signals aren't crossing the splits.
Arrange your power/ground pins such that if you reverse the connection end-for-end or plug a cable into the wrong connector you won't short power to ground.
