Knowledge Base - How does the analog multiplexer work ?

Weeroc read-out chips allow analogue multiplexed output once the ASIC as triggered for serial analogue charge measurement outting.

The multiplexer is composed of a read shift-register that sequentially connects the different analogue memory to the analogue multiplexed output.

The read registers can be daisy chained on several ASIC to multiplex several ASIC input into one single analogue output.

3 digital inputs and 1 digital output are used to control the read register:

  • RSTB_READ which reset the shift register, unhooking any connected channel to the multiplexed analogue output and setting that analogue output to high impedance
  • SRIN_READ which is the shift register input used to propagate a 1 along the register
  • CK_READ which is used to shift the register, therfore changing the output signal from channel N to channel N+1
  • SROUT_READ which provides the propagated 1 when the last channel of the ASIC is connected to the multiplexed analogue output

It is possible to connect several ASIC to the same register by connecting all multiplexed analogue outputs to the same line and by connecting SROUT_READ of one ASIC to SRIN_READ of the next ASIC. The 1 connecting a channel to the multiplexed analogue output will propagate along several ASIC allowing a multi-chip multiplexing.

Connecting several channel simulteanously to the analogue multiplexed output will cause a conflict and analogue data provided will not be valid, user has to ensure that their is only one connected channel at the same time.

The following chronogram whows how to use the read register to multiplex the analogue charge measurement.

read register chronogram

 

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Created : 2015-02-18 15:16:35, Last Modified : 2015-02-18 15:35:28

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