Effect of flat cableto MPPC signal

S. Uozumi (Kobe)Jun-6 2008 ScECAL meeting

Readout cable

Idea 1:

Idea 2:

Idea 3: Just adopt long flat cable with MPPC(as done in DESY BT).

Objective

• How the MPPC signal skewed by passing through industrial-standard FPC cables and connectors?

• Any reflection clearly seen?• This will determine (or give a feeling) specs of

our readout flat cable (inpedance, length…).• Electrocal cross-talk between adjacent lines

on the flat cables?

Setup• 20-lines FPC cables with 15cm length 1.25mm pitch and

FPC connectors are used.

FPC (15 cm)

FPC (15 cm) FPC (15 cm)

Relay board

MPPC

MPPC

Readout circuit

Signal connected toOscilloscopeThrough x63 amp

FPC cable FPC connector

Dark noise signal with different cable length

With two cablesAnd relay board(30 cm)

With one cable(15 cm)

Electrical cross-talk

Signal channel Adjacent channel

Amount of electrocal cross-talk on the flat cable is at leastbelow noise level.

Conclusion Of course those checks are not perfect, but we can somehow learn :– Better to set the cable inpedance to 50ohm, even if it makes production cost ~20% higher. (it was NOT considered at the DESY BT.)– Electrical cross-talk on flat cable is not significant

level.– I suppose to go ahead with idea-I, but with 50ohm

flat cable, not industrial standard FPC cable.– But, if the cable length can be short enough, taking idea-3 is also possible(but with 50ohm

cable).