From: Marc Dejardin [marc.dejardin@cern.ch]
Sent: 17 November 2005 12:42
To: Dave Cockerill
Cc: Magnus Hansen
Subject: Re: Testing the VFE cards from E0' in 2004

Attachments: VFE_MGPA_sch.pdf

Dave Cockerill wrote:
> Hi Marc,
Hi Dave,
> 
> 3 questions concerning E0prime:
> 
> SC03 had 5 barrel 'early' VFE cards, with hand written labels on the 
> copper screen (side opposite the cooling bar) with 'Card 1', 'Card 2', 
> etc.
> 
> 1) We would like to calibrate these VFE cards, using an external 
> capacitor, to give a calibration for our VPT yields in electrons per 
> MeV.
Good

> 
> 2) Looking at E0prime from the back, do you remember if card 1 would 
> have been top most or bottom most (sorry to ask such minutiae so long 
> after the event!). I attach photos as an aide memoire.
If I was not completly stupid, I should have put the card 1 (or lowest
number) in the position 1 and then in increasing number. The position 1 is in the position near the LVRB.

> 
> 3) We have asked Magnus how we can power up these early barrel VFE 
> cards (they were used with an old FE card with FPGAs).
> 
> His proposal:
> 
> Use new LVR card - should be OK
> Use new FE card - should be OK
> He worried that the FE card might pull too much current.
> However we only intend to calibrate 1 VFE card at a time.
> 
> Do you agree with Magnus?
I think that you need a couple (old FE-FPGA/old LVRB) or a couple (new FE-asic/new LVRB).
With old FE/old LVRB you will get 3.3 V for the output buffer, with the new FE/new LVRB you will power the output buffer in 2.5 V which has shown to work despite the fact that it is out of specs.

Please ask Lubo for confirmation for the coreectness of the schematic version.

> 
> Tony would like to do this this afternoon, Thursday.
> 
> Thanks,
> Dave.
> Ps 3 other cards, for SC04 (15 channels with APDs) - we could also 
> calibrate these in the same way, if you agree.
No problem
Regards
Marc