Re: fADC

[Mitch Newcomer <mitch@hep.upenn.edu>]

Our target will be to get this design, as is, fully ready for 
submission.   Then circle back and look for an obvious spot to
include switchable  X5 gain. ( I am assuming that is with 1/5 the 
dynamic range.)   This approach  will allow us to encounter
every last problem prior to sending it to MOSIS before adding new 
features.   At the moment everything except the
Cadence  Assura LVS checker for NWELL resistors is working.   We only 
use NWELL resistors  in non signal path
filtering where precision in setting absolute  R values is unimportant.  
In fact they are not necessary for this design.   Nandor
is chasing the error that causes LVS to crash and Nishant is finishing 
up the single channel layout.  
  - Mitch

Gerard Visser wrote:
> Hi Fernando,
>   I'll get some kind of block diagram together. It will be needed 
> anyway, not only for the review; it's good to get it done now. I am 
> expecting feedback from a vendor soon on some parts pricing, I'll 
> probably wait for that first.
>   I complete acknowledge, we did not discuss the two gains option with 
> Mitch, and it would certainly be a change that requires some extra 
> work from him. I guess I did not really appreciate that we would need 
> such a large (~6) gain factor difference between cathodes and anodes, 
> but it looks that way at least based on recent results. We need to 
> nail this down further before asking Mitch to actually do anything 
> about it. Perhaps it can be accomodated only at the ADC board, but as 
> you know this is not optimal from the noise perspective. It may not 
> matter very much though - we should be able to easily calculate and 
> add the corresponding amount of extra noise into the measured samples 
> and see how much the cathode position resolution is degraded, if at all.
>
>     Gerard
>
> p.s. I'll post the block diagram and spec slides to the portal in a 
> few days, when I have it.
>
> Fernando J. Barbosa wrote:
>> Hi Gerard,
>>
>>    Thanks for the specs on the fADC. A block diagram would be really 
>> great and I would need it sometime within the next week (maybe 2). 
>> The review is on March 6th but Elke would like to have the slides 
>> distributed by the end of next week for comments. I am planning on 
>> running the electronics slides by you to get your feedback.
>>
>>    On another note, I called Mitch yesterday after he replied to my 
>> email. He was surprised about the gain for the cathodes as that was 
>> never mentioned to him. He will look at it after the prototype is 
>> complete because it affects a lot of the design, as you know. It may 
>> be that the x5 gain has to be provided on the fADC just like you do 
>> now. He also didn't see a problem with sharing the spice net and it 
>> also helps with reviewing the final design.
>>
>> Best regards,
>> Fernando