Projects Document 780-v23

8-channel ASDQ-based wire chamber pcb

Document #:
Document type:
General Documentation
Submitted by:
David Christian
Updated by:
Shou Miyasaka
Document Created:
10 Nov 2009, 15:43
Contents Revised:
01 Jul 2011, 07:50
Metadata Revised:
18 Jan 2012, 11:29
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Front-end card and level adapter for SeaQuest drift chambers. Version 4 of the ASDQ card has DC coupled inputs (no transformers, no capacitors) and only one "ground."
Design by Sten Hansen.

The ASDQ digital outputs are the open collectors of a "long tail pair." When pulled up to a voltage sufficiently greater than -3V (the negative rail of the ASDQ output circuit), 3mA flows through one or the other of an output pair. The level adapter board terminates each side through 50 ohms to approximately .6V. The resulting logic levels at the input to the LVDS receiver chip are ~0.6V & ~0.45V.

The level adapter also provides voltages, receives signals, & facilitates tests of the ASDQ-based front end cards.

The level adapters will be held in a 9U enclosure and be powered by 24V. The level adapters will be controlled over Ethernet. The first card in the crate will be connected to an Ethernet cable; subsequent cards will receive control signals via a daisy chain of telephone-style cables. The ASDQ test pulse signal will be generated in response to a command and/or by a TTL (3.3V) signal input to the first level adapter. The TTL signal will be daisy chained to the rest of the cards in the 9U enclosure with short lemo cables. The last card in the chain will require a 50 ohm termination.

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Notes and Changes:
Dummy load cards made:
2 60 ohm 1/8 watt resistors in parallel +3V--GND
4 78 ohm 1/8 watt resistors in parallel -3V--GND
should be about 2x ASDQ card current from each bias voltage.
Related Documents:
  • Projects-doc-779: ASDQ
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