Re: questions (fwd)

[Frederick Gray <fegray@berkeley.edu>]

On Fri, Mar 31, 2006 at 07:23:39PM +0200, Ron McNabb wrote:
>  Hi Peter,
> Yes, we have the the ECL/LVDS input FIFO. It will accept either one. The 
> only other option is NIM inputs.
> Ron

Dear Peter and Ron,

I just removed one of the little input daughtercards.  It contains two
National Semiconductor DS90C402 LVDS receivers and a little bypass capacitor. 
The absolute maximum rating on this device allows input signals from 
-0.3 V to Vcc+0.3 V.   Consequently, ECL levels of -1.75 V and -0.9 V are out 
of range and may destroy the chip.  I suspect that there are ESD protection 
diodes on the pins, and that a negative signal causes a current to flow
through them.  The absolute maximum rating would be set by the power 
dissipation limit in the diodes.  (The recommended operating range is 
from 0 V to +2.4 V.)

The reason for the question is that, well, I connected some ECL signals
to this FIFO for a few minutes yesterday.  I do not know whether I
actually caused any damage, but it certainly explains why there was no 
data collected.

(For Ron: The FIFOs used for the muCap ePC readout have an ECL receiver 
instead -- ON Semiconductor MC10H125P.  For some mysterious reason, all of 
these chips were destroyed during the interval between runs.)

Thanks,

-- Fred

-- Fred Gray / Visiting Postdoctoral Researcher                 --
-- Department of Physics / University of California, Berkeley   --
-- fegray@berkeley.edu / phone 510-642-2438 / fax 510-642-9811  --