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analogdevicesinc / m1k-cad

ecad for the ADALM1000
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Rev C shows CHA_2.5V connected to UB11 #3

Closed shabaz123 closed 9 years ago

shabaz123 commented 9 years ago

Hi! I don't have cadence software, so can only look at PDF schematics. Which is the latest schematic in PDF? I looked in the 'old' folder, and there is a rev C schematic there. I noticed CHA_2.5V is connected to integrated circuit UA11 (as expected), but also seems to be connected to UB11. Is that intentional?

There is a CHB_5V power signal, but that is not connected to UB11, it only goes to the connector.

I'm guessing the purpose of the CHA_2.5V connection is to allow self-calibration when it is switched in using the digipot?

What is the purpose of the CHB_5V connection? Is it just to be a general purpose connection, not actually related to channel B?

Thanks!

itdaniher commented 9 years ago

Hello there!

https://github.com/analogdevicesinc/m1k-cad/blob/master/02-037760-01-d-1.pdf is the latest schematic.

The connection from the buffered 2v5 supply to UA11 and UB11 allows the output switches to offer a 50o biasing to the 2.5V virtual ground, switchable onto both channels A and B. This concept is briefly described at https://wiki.analog.com/university/tools/m1k/hw#output_stage - if you can think of better wording, feel free to edit! The 5V supply is simply a buffered / fixed voltage rail.

In short, the connector naming reflects the electrical grouping with regards to the original amplifier - you didn't find a bug, just a hidden (for now) feature.

Regards! Ian

PS - Allegro Viewer can be grabbed for free from http://www.cadence.com/products/pcb/pages/downloads.aspx, runs fine in a Virtual Machine.

shabaz123 commented 9 years ago

Hi Ian,

Thank you for the information and super-quick response! Thank you for this great project - very exciting times, exploring with the hardware and software currently!