Power on two, cable connected PCBs

Question

I'm making a device that will require two PCBs. One will be smaller, and pretty much just be the sensor that I'm testing. Almost like an evaluation board. This smaller PCB will be connected or inserted to a larger PCB which has all of the other components (some signal processing, biasing, a little microcontroller for data acquisition, etc).

The problem is that the sensor requires 4 different DC power supplies. Can I put power planes on both the smaller and larger PCBs, and connect them with a cable? The actual data coming in and off the sensor will use some high-density PCB-PCB connector, maybe an SO-DIMM architecture like this:

I feel like I shouldn't use these connections for power lines though. The sensor is fairly power hungry, so I'd have to send a lot of current through those tiny pins, which seems like it wouldn't be the best idea. So as I see it, I've got 3 options:

1. Put the voltage regulators on the larger PCB, and connect them to the smaller PCB through shielded coax cables.

2. Put identical voltage regulators on the smaller and larger PCBs, and connect just a single power and ground line between them (I'm thinking this one isn't the best).

3. Put voltage regulators on the smaller PCB, and connect them to the larger PCB through shielded coax cables.

Ideally, I'd want to use power and ground planes on both of the PCBs, to help with noise and losses over traces. But I have a feeling like I'm missing something important. Any advice would be welcome.

Answer 1

The pins on a so-dimm connect can handle 0.5 Amps to 0.75 Amps per pin. A pin on a PCI connector can handle 1.1 Amps. They are not as weak as you would expect. Use multiple pins if you need more current. Yes you could also use a local power regulator and higher voltage lower current through the pins, or a combination of both techniques.

Typically power input to a daughter card/carrier setup like this is the power comes into the carrier and passes through the daughter card connecter. Extra cables is only used on retroactive designs (think PCI E supplemental power connection) when the needs exceed the spec.

Answer 2

it's a good practice to separate power and signal PCBs, separate high voltage used to power the sensor on the larger PCB and use some good connectors that can support high current (I used XT-60 and is pretty good, you can also use fork terminals). keep on the good work!