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RPL1116 (MSO1000Z) and PLA2216 (MSO5000) Active Logic Probe teardown

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dren.dk:
Here's my take on an 8 channel lmh7324 based pod, highlights:

* Still single-sided load, for ease of assembly with a super-generous courtyard around the QFNs for ease of rework, should it be needed, but at 40x42 mm I don't really think it needs to be any smaller.
* I went with a 26 lead, 1 mm pitch ribbon and IDC connectors towards the scope, because I don't want to deal with the nightmare of laying out the 1.27mm pitch header and 26mm is narrow enough for me:)
* The inputs are via a 2x8 2.54 mm pitch female socket, with half of the pins being ground, that should make it easy to plug in a single-use adaptor board or individual probes, I want to plug in my inputs from the top, but it's just as easy to use the same foot print for an angled header or socket if front-entry is desired.
* I want to laser cut an acrylic sandwich case, which basically requires a hole for a screw in each corner, so the board grew 10 mm in width because of that.
* To use the space between the mounting holes for something I stuck a crude voltmeter on the board in the form of an ATtiny85 and 10 charlieplexed LEDs, so it's fast and easy to verify that the threshold voltage is set correctly.
* The Kicad project is on gitlab here: https://gitlab.com/dren.dk/mso5k-la-pod/tree/master/lmh7324-8ch

Roast my layout:)

Rerouter:
Ok, 1.27mm non-inline header done, I'll make up my ribbon breakout board probably tonight.

oliv3r:
Beautiful! and really good use of that attiny!! Just 2 question I have.

Why not make it a nice 50 x 50 mm, gives you more room to play with bigger ground cooling plane, and allt hese cheap PCB services houses have their minimum size set to 50 x 50 anyway. Size is probably smallest concern anyway, right?

One question remains, I do not recall the pinout from the scope-end; but do remember the original 2 channel LM's they 'split' the inputs between channel 0 and 8 for the first LM. The second LM goes to 1 and 9 and so on. Now if that's also how the signal enters, then it does not matter I think how you do it.

But with this new redisgn, you will end up with a really odd UI don't you think? So bit 0 - 8 on your probe, will correspond to the odd bits, and 9 - 16 to the even?

Rerouter:
That's why the breakout board idea, to remap the channels back to the correct order, 2 layers is a pain for routing crossing differential pairs with decent impedance. So at this point I've drifted to 4 layer

dren.dk:
I started out making my breakout board in 2 layers, but then I noticed that jlcpcb allows me to panelize two pods and a breakout for 15 usd, which means that I can get 4 layer boards for 20 pods and 10 breakout boards in black for 60 USD, so I'm going with 4 layers for my breakout too.

I've been trying to hit the correct impedance with the stackups offered by jlcpcb and I've taken the time to length match the wires of each pair, but not the inter-pair length.

Seeing that it was possible to route the 1.27mm pitch header, I switched to a 1.27 mm pitch header in smd and that freed up an enormous amount of space which made it much easier to route.

The idea with the breakout is to reorder the pin outs so the channel numbering on the scope fits with the numbering of the pods and channel 0-7 goes on one pod and 8-15 goes on the other

My breakout is designed to sit flat against the front of the scope with a tall female socket on the bottom, but it can also be used with a short cable to the scope.

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