TMUX1119: Peaking at the output of TMUX1119DCKR

HARI T O1

Part Number: TMUX1119

Dear Team,

I am using TMUX1119DCKR in one of my projects.

My I/P is S1=3.6V and S2 is 1.8V.In our lab circuit, I/P is provided from a Power analyzer from Keysight.(https://www.keysight.com/in/en/product/N6705B/dc-power-analyzer-modular-600-w-4-slots.html)

In the TINA TI reference design I can see a 50ohm series resistor in the I/P of S1 and S2 . May I know the use of it?

Select is driven by a CLK of Amplitude 5V and Max frequency is 400Khz.

I am observing some peaking at high(3.6V ) and Low states (1.8V).

May I know is expected behavior or is there any way to solve this problem.

Please find my TINA TI simulation file.

mux.TSC

Regards

HARI

over 3 years ago

0 Rami Mooti1 over 3 years ago

TI__Mastermind 27798 points

Hey HARI,

In the TINA simulation file, the resistors are supposed to simulate the internal resistance of the supply that is feeding the signals into the mux. They aren't tied to the actual function of the multiplexer, so they can be changed as your needs require.

With regards to the 'peak' this looks like an overshoot condition. Although it's very minor (looks to be in the 14mV range. Is this that impactful on your system?
Typically an overvoltage condition is due to inductance on the line. There is probably inductance added to the model which is why you're seeing this. You should expect inductance in real life applications as well from just the traces and wiring. You can mitigate this often with just a series damping resistor. The 50ohm one currently there may just not be enough. Have you increased that value to see the effects?

We also have an FAQ on debugging overshoot in switching events
https://e2e.ti.com/support/switches-multiplexers-group/switches-multiplexers/f/switches-multiplexers-forum/863546/faq-debugging-and-fixing-overshoot-in-switching-events

Thanks,
Rami

0 HARI T O1 over 3 years ago in reply to Rami Mooti1

Expert 1355 points

Hi Rami,

I did not keep any series damping resistors.

I will keep and test it tomorrow.

The O/P of this SPDT is going to an SPST switch.I think I need to keep there also.

I will update you tomorrow.

Regards

HARI

0 HARI T O1 over 3 years ago in reply to HARI T O1

Expert 1355 points

Hi Rami,

I kept a resistor of value 61.9 in series with S1 and S2 and solved the issue of overshoot and undershoot.

May I know how that resistor is reducing the overshoot and undershoot

Regards

HARI

0 Rami Mooti1 over 3 years ago in reply to HARI T O1

TI__Mastermind 27798 points

Hey HARI,

Glad to see it helped!
There's actually a good and rather extensive app report on this Bus-Interface Devices With Output-Damping Resistors or Reduced-Drive Outputs. The theory here is that you're limiting the reflection with impedance matching.

Thanks,
Rami

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TMUX1119: Peaking at the output of TMUX1119DCKR