AMX Schematics & Layout

[Carl-NC]

Here is an initial try at a more-or-less complete schematic. I still need to add some provisions for connecting to a micro. I believe the AFE is pretty much the same as I posted before. The TX schematic is close to what I've discussed, I had to make some minor changes to the integration loop to accommodate the eventual use of an ADC & DAC for digital control. At real high level, the TX looks like this:

The power circuitry is as discussed before. Here's a block diagram:

The positive boost is an option if I decide to pursue a single-cell lithium battery like a 26650. Right now I'm leaning toward (2) 18650 which makes the positive boost unnecessary. An identical boost has been added to drive the TX switches. Since 2 switches will likely be 1200V SiC MOSFETs they usually require a higher drive; I'm expecting 12-15V.

Overall, including a micro and audio, I think I can get this whole design under 2 watts. Either (2) 18650 or (1) 26650 has ~20W-hrs of energy so this will be 10hrs of run time on a charge.

AMX_SchRev0.1.pdf

[Carl-NC]

I forgot to mention, the FET switches in the TX circuit are just place holders. I have not selected the actual devices, still looking at options.

Also, based on feedback in the TX thread, there are pending changes to the TX sampling circuitry for tilt correction. See this post for details.

[Carl-NC]

Here is Rev 0.2. Based on feedback from Willy & Olly (see the TX thread). I've changed the simple sample-holds into a differential integrator to get more resolution for the tilt measurement. Also put in some real FET switch numbers and fixed a few other things.

AMX_SchRev0.2.pdf

[Carl-NC]

Layout is progressing, though slowly. I've made it to the hard part, where I need to figure out the power planes. Total board size is currently 100x150mm.

[GeoMax]

Hi Carl,

If you need a good PCB size for your detector projects and if all the components fit, choose one of the following board sizes.

1) PCB size 134x70mm (LxW). This PCB size fits nicely in many different and easy available enclosures of the size 160x80x56-90mm (LxWxH).
2) PCB size 151x98mm (LxW). This PCB size fits in an standard enclosure of the size 160x110x90mm (LxWxH)
3) PCB size 145x75mm (LxW). This PCB size fits for the Hammond 1591XXDBK enclosure series 152x82x51mm (LxWxH)
4) PCB size 172x110mm (LxW). This PCB size fits for the standard Pollin enclosure of the size 200x120x90mm (LxWxH)

[ivconic]

Hi Carl,

If you need a good PCB size for your detector projects and if all the components fit, choose one of the following board sizes.

1) PCB size 134x70mm (LxW). This PCB size fits nicely in many different and easy available enclosures of the size 160x80x56-90mm (LxWxH).
2) PCB size 151x98mm (LxW). This PCB size fits in an standard enclosure of the size 160x110x90mm (LxWxH)
3) PCB size 145x75mm (LxW). This PCB size fits for the Hammond 1591XXDBK enclosure series 152x82x51mm (LxWxH)
4) PCB size 172x110mm (LxW). This PCB size fits for the standard Pollin enclosure of the size 200x120x90mm (LxWxH)

Another solution is we to design our own enclosure and 3D print it.
So I propose total freedom in designing the pcb with no compromises on account of quality of pcb design.

[Carl-NC]

For me, this first board is for bench testing. It will be mated with some kind of micro eval board. But if I can, I'll try to make it fit a particular box.

[Olly]

Here is Rev 0.2. Based on feedback from Willy & Olly (see the TX thread). I've changed the simple sample-holds into a differential integrator to get more resolution for the tilt measurement. Also put in some real FET switch numbers and fixed a few other things.

[ATTACH]n411310[/ATTACH]

Hi Carl, I was wondering whether it might be advantageous to increase the op amp supply voltage to somewhere closer to +/- 12V in order to make full use of the wide input voltage range of the ADC?

I expect this should improve SNR somewhat.

Regards,
Olly

[Carl-NC]

When I did a quick read of the data sheet I was under the impression that the total bipolar input range was +/- 10.24V, or +/- 5.12V per input pin. Fig 5 & 6 suggest that it is actually +/- 10.24V per pin, so we could increase the opamp supplies to +/- 10V. All of the power supply chips can handle this so it is a matter of changing some resistor values. All of the opamps can also handle this except for the MAX412, but that was just a placeholder anyway until I decide on the real opamp. So the design does not need any changes to support +/- 10V. Supporting +/- 12V requires adding an external reference to the ADC and I'd rather not do that right now.

[Olly]

When I did a quick read of the data sheet I was under the impression that the total bipolar input range was +/- 10.24V, or +/- 5.12V per input pin. Fig 5 & 6 suggest that it is actually +/- 10.24V per pin, so we could increase the opamp supplies to +/- 10V. All of the power supply chips can handle this so it is a matter of changing some resistor values. All of the opamps can also handle this except for the MAX412, but that was just a placeholder anyway until I decide on the real opamp. So the design does not need any changes to support +/- 10V. Supporting +/- 12V requires adding an external reference to the ADC and I'd rather not do that right now.

Thanks Carl, good flexible design

[Carl-NC]

Here is Rev 0.3 of the schematics. No major changes, but a lot of detail changes in order to finish the layout.

AMX_SchRev0.3.pdf

Also, I have completed the layout. It is also called Rev 0.3 and I will leave it for a while so others can review and offer feedback. I also like to chew on a layout for a few days before I send it to JLC.

AMX_GerberRev0.3.zip

Here is a preview:

[Carl-NC]

I did a quick-check with JLC, 5 boards will run $40 USD plus shipping. That's not bad; it's 4 layers and 5.6" x 3.75" (143mm x 96mm).

Most passives are 0805, a few are larger. Chips are SOIC and SOT23, except for the ADC which is MSOP-16. I just noticed D7 & D8 are SOD323, I'll change them to SOD123.

[wtrk]

Hello Carl.
Could you please share if possible BOM and CPL files for assembling directly to jlc

[Carl-NC]

It will take some time for me to clean up the BOM and get proper part numbers entered. I'll post it when done.

[Mdtoday]

Carl,
I had a look over your PCB layout and noticed a couple of minor things.
Two or three tracks around D1,D2,R2 could be beefed up to match other tracks.
Maybe increase track width section at pads on the SPI connector, purely based on my experience with JLPCB, PCBWAY boards in the past where, thin tracks to larger connector pads are not all that reliable….not a game stopper but maybe worth increasing track width section just at pads.

Nice work on the layout btw.