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Yet More on Clocks

Explore a new bias network for AC-coupled BCO clocks on stavelets, predicting amplitudes, and testing multiple input amplitudes for optimal performance gains. Considerations and challenges in modifying circuit boards.

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Yet More on Clocks

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  1. Yet More on Clocks Peter and John

  2. New bias network for AC coupled BCO • Original version left 120mV DC bias between the two inputs • Alternative shown suggested by Dave Nelson and Dieter Freytag (SLAC) • Implemented on the stavelet by PWP (for H0 only – others unchanged) using 0603 components mounted vertically 2V5 33k 33k

  3. How did we do? H0 post blocking C, 68R ET, 100R BT H0 Recovered BCO, 68R ET, 100R BT => Looks great! Next: vary back termination (0R < X < 100R) to explore margins

  4. H0: Recovered BCO, 56R ET, X1 BT H0: BCO pre blocking C, 56R ET, X1BT H0: BCO pre blocking C, 56R ET, X2BT H0: Recovered BCO, 56R ET, X2BT

  5. H0: Recovered BCO, 56R ET, X3BT H0: BCO pre blocking C, 56R ET, X3BT H0: BCO pre blocking C, 56R ET, X4BT H0: Recovered BCO, 56R ET, X4BT

  6. Can we predict amplitude at capacitor inputs, using MLVDS driver, after 24 drops? Amplitude (mV) 380mV Drop number

  7. Crystal Ball Time • For a 24 drop stave built to the same tape geometry, we can extrapolate the stavelet data to predict the amplitude at the end of the BCO bus • Predict 380mV, 56R end term, 100R back term • We have tested the BCC board with the new bias network for several input amplitudes • 340mV gives 51.8% duty • 186mV gives 52.3% duty • 120mV gives 54.6% duty (limit for ABCN) • Prediction • A stave using BCC V2 with the modified circuit should work just fine! Even looks like we have a factor >2 safety.

  8. This looks great – but... • Caveat • Need to try a chain of many boards with the new circuit to confirm this, not just one • Modifying the card on the stavelet was very tricky, it would be much safer to do this with an alternate“testvehicle” • Any volunteers with suitable facilities? • We could maybe replace the BCC boards on the stavelet with new ones? • I would strongly recommend this be tested before any decision be made to leave BCO clock regeneration out of BCC V3. • Having said that – it looks like we won’t need it ;-)

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