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TMUX1308: TMUX1308 Driving a reed relay

HARI T O1
Expert 1395 points
Part Number: TMUX1308
Other Parts Discussed in Thread: TMUX1208

Dear Team,

I am using TMUX1308 for driving a reed relay. Below is my Circuit. In the simulation, it is working fine.

In real circuit selection lines and Enable is coming from Arduino.

Enable(Active low) will be connected to Vcc via a pull-up resistor of 10K.

May i know this circuit is fine or do I need to make any changes.

Regards

HARI

  • 0
    TI__Mastermind 29498 points

    Hey HARI,

    Looks good for the most part. I typically wouldn't recommend driving your I/O signal from your VCC directly though. There could be transients when switching the load. This isn't a problem on the Enable pin since it seems you're just holding it high the entire time plus the fail-safe logic will remove any powering sequence issues that may come from the EN receiving a signal before the device is fully powered up. 
    I'd also recommend placing a decoupling capacitor on the VDD pin. The datasheet recommends a 0.1uF cap. This should be placed as close to the device as possible to filter out any noise and increase reliability. Would you mind sharing what's the application here? 

    Thanks,
    Rami

  • 0 in reply to Rami Mooti1
    Expert 1395 points

    Hi Rami,

    This ckt is a part of our ASIC evaluation board. In this board, 5 ASIC parameters are measured in a TDM manner.

    ASIC outputs will be connected to a relay. This relay driving BJT is turned on and off with the help of this mux.

    This MUX is controlled by an Arduino Nano.

    Regards

    HARI

  • 0 in reply to HARI T O1
    TI__Mastermind 29498 points

    HARI,

    Thanks for sharing the application. We're always interested to hear where are devices are being used.
    As mentioned, the circuit looks good with some minor recommendations that may not affect simulations but would help a real life circuit. At the very least, the decoupling caps offer a huge benefit at very little cost. Asides from that, sounds like you're good to go!

    Thanks,
    Rami 

  • 0 in reply to Rami Mooti1
    Expert 1395 points

    Hi Rami,

    Thank you.I will make the changes you suggested.I have one more question . This is regarding TMUX1208 and Arduino Logic compatibility.

    Please see my question below. This board will be sitting outside the oven.

    Question

    I am using Arduino Nano for driving TMUX1208. The address lines, Enable and I/P are coming from Arduino Nano.

    The output of the MUX is used for driving a BJT which is used for driving a relay. The Vil of TMUX1208 is 0.87V and the Vol of Arduino nano is 0.9V(IOL=20mA, VCC = 5V).

    May I know will cause any issues in my circuit. I want the transistors(MMSS8050-H-TP) to be off when EN is low.

    The input leakage current of TMUX1208 is ±0.005uA. So I assume Arduino Nano is Vol will never go to 0.9V. Please correct me if I am wrong.

    MY CIRCUIT

    DC SPEC of Arduino Nano

    DC Spec of TMUX1208

    Regards

    HARI

  • 0 in reply to HARI T O1
    TI__Mastermind 29498 points

    HARI,

    You are correct in your thinking. The leakage means that there is a higher impedance there. This should limit your logic input and keep you well below the threshold when the line is pulled to ground via the 10k resistors.

    Thanks,
    Rami

  • 0 in reply to Rami Mooti1
    Expert 1395 points

    Hi Rami,

    Thank you...

    Happy New year in advance.

    Regards

    Hari