MUX509: MUX 509 input output communication

Hi,
Let me put my question clearly here in short.
As same channel can be used as input or output (Ex. S3A and DA both can be used as input /output) Is any time limit between switching of Input to output on same channel?. If I am using DA as output and now some acknowledgement come on DA (as an input) so what is there any time limit.?

Because I am not getting acknowledgement on S3A(while as input) considering this scenario.

Thanks

Hijack,

The MUX509 device is a passive FET switch which means it doesn't have any drive, repeat, or signal conditioning capability. It will simply pass the voltage it sees on one side of the FET to the other.

Determining input or output of the MUX509 is up to the user on how they connect their signal source and load or in your case the TX or RX. There shouldn't be any issue from the switch in the direction of communication. A quick way to check is to remove the switch and short the signal path to see if the problem still exists.

What are you connecting to the switch? Do you have a schematic or diagram?

Are you able to measure as scope shot of the signals in and out of the switch to see if there is any distortion between the source (SxB) and drain (DB) of the FET switch?

Thank you,
Adam

 Adam,

We have advanced in this and now able to receive the pulses on receiver side. But there is still some issue.

I am herewith attaching simplified schematic and waveform and further explaining the queries.

I have attached waveform with using the Mux and another without(bypassing) the Mux.

Here I am connecting DALI based LED driver on the receiving side.

1. When I applied command bypassing the Mux the received waveform signal amplitude level is approx 12.5V.

    But when I connected through Mux. received signal amplitude is approx. 7.5V .

What could be the reason behind it. Signal amplitude level of transmitting pulses is OK as you can see in both the waveform.

I have applied 24V VDD to Mux and S3A channel has constant 15V. S3B is for transmitting and receiving

the signal.

What could be the root cause for this behavior

HiJack,

This is not expected. If the transmit signals are not different when you bypass the mux vs going through the mux, would not expect the receive signals to be different. If you saw smaller amplitude going through the switch for receive signals I would expect to see that same effect on the transmit signals

The on-state resistance of the MUX509 is typically 125 ohms. If you are passing 25mA of current through the switch with 125 ohm resistance you can expect a voltage drop of about ~3V across the switch. Do you know if the drive strength is different between the transmit or receive drivers?

Do the voltages A0 and A1 remain at the same levels in both cases?


Thank you,
Adam

Hi Adam,

1. The current passing through is in between 1.5 to 2mA on both the channel. So I understand that there should not be significant drop considering current and voltage.

2. I have hardwired A0 to GND and A1 to 3.3V to select S3A and S3B.

 Still I am not able to solve the issue.

Thanks

Hijack,

The odd thing about your experiment is that your first transmit pulses are not effected if there is a switch or not.  Only the receive pulses are effected by the switch.  If the switch is causing the issue I would expect it to be causing issues in both cases because it is a passive FET switch.   

Have you tried debugging the problem with a mechanical mindset vs electrical?  Have you tried swapping out a new IC or putting an IC on a different board? 

What do you think is different between the DALI selection transmitter sending information across the bus vs the LED driver sending the received information across the bus?

Thank you,

Adam

Hijack,

Have you run any additional experiments? Do you have an idea of the root cause of the issue?

Thank you,
Adam

Hi Adam,

I was quite busy in last few days in other activity so could not continue on this.

But Last update was that I could not succeed on that and I will start again to find out the root cause. 

I will update you and come to you for further results and queries.

Thanks

Hijack,

Do you have an update from further testing?

Thank you,
Adam

Hijack,

I'm closing this thread due to inactivity. If you need additional support you may respond here and it will reopen issue or you may start a new thread.

Thank you,
Adam