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TMUX7462F: Supplying the VFP pin with a series diode

İbrahim Mete
Prodigy 50 points
Part Number: TMUX7462F

Hi,

TMUX7462F protects from overvoltage beyond the VFP+VT
I need to protect a 5V level signal with GND-0.3V to 5V+0.3V (absolute max) range.
If I connect VPF pin to 5V supply, max voltage on the signal can go up to 5.7V before cut off.
Do I need additional 4.6V supply (or divider+buffer) to supply VFP?
Or can I do this with a simple series 0.4V~0.5V forward voltage drop diode on the 5V supply line? And maybe one more series diode needed for the VFN pin also to protect GND-0.3V?

(TMUX7462F will be supplied by 12V signle supply.)

And a second question when will be available this device in the stocks?

Regards,
Mete

  • 0
    TI__Expert 3515 points

    Hi Mete,

    What is the voltage range for the signal that you are switching? The VT value is listed as a typical and can vary so it is best practice to set the VFP level to as close to the maximum signal voltage range as possible. Either method (divider+buffer or diode) to reduce the voltage should work.

    You can subscribe on ti.com to be alerted when the product is in stock again.

    Thanks
    Tyler

  • 0 in reply to Tyler McGuire
    Prodigy 50 points

    Hi,

    I want to protect the 5V DAC outputs that connected to a connector pin.
    And full range is used (0V to 5V)

    If the VFP is around 4.5V and VFN is around 0.5V then TMUX7462F should protect the signal in the -0.2V to 5.2V range if I understand correctly.


    VFP and VFN current specified 10uA typically in the datasheet.
    I have tried to calculate a diode(MA4X194) voltage drop and compared the VT/temp graph.
    According to this calculation if the VFP current is 10uA then 0.3V over-rail protection possible up to 70C.
    If VFP current would be 100uA then it will protect up to 120C.

    Maybe a better VF fitting diode should be selected or divider+buffer method should be used.

    What do you think about this method? What do you recommend?

    Thanks, Regards,
    Mete

  • +1 in reply to İbrahim Mete
    TI__Expert 3515 points

    Hi Mete,

    Your understanding is correct, with VFP at 4.5V and VFN at 0.5V then the clamping voltage should be around 5.2V and -0.2V based on the typical VT value.

    If the application calls for temperatures over 70C, then a diode with a lower drift over temperature would be recommended. Or, as you mentioned, a buffer+divider may also be the better option over temperature since you can select resistors with very tight tolerances and a buffer with a wide temperature range.

    In general, I would recommend evaluating either option on a board because it sounds like this application calls for tight clamping specs. TI offers an EVM kit for this device to help with this.

    Thanks,
    Tyler