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Original question:

TMUX1511: Tolerant voltge on input/output pins

TMUX1511: TMUX1511 and PAL/NTSC video

user5867317
Prodigy 90 points
Part Number: TMUX1511
Other Parts Discussed in Thread: TS5A22362, TS12A4516

Hello,

We're currently testing the TMUX1511 with a PAL/NTSC video.

It's currently working but we are wondering about the analog sync tip which goes down to -300mV (so below the recommended operating conditions).

The datasheet (absolute maximum ratings §6.1) shows Vs or Vd accept down to -0.5V. but note (1) shows it's not guaranteed this will work for all devices. Do you confirm this statements?

Do you have suggestions we could use to stay in the recommanded conditions?

Thanks.

Sébastien

  • 0
    TI__Expert 5660 points

    Hello Sébastien,

    To confirm, VS,VD of -300mV is outside of Recommended Operating Conditions (min 0V). As you pointed out in note (1) of the Absolute Maximum Ratings: These are stress ratings only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.

    You may choose to use a diode or similar clamping device/circuit at S,D pins to limit voltage at that node to >0V to comply with recommended operating conditions.

    Best regards,
    Kate

  • 0 in reply to Kate Dickson
    Prodigy 90 points

    ok. Thanks Kate.

    The thing is we need this excursion in negative voltage as this is part of the analog signal NTSC or PAL. WE don't want to suppress it by using a diode.

  • 0 in reply to user5867317
    TI__Expert 5660 points

    Hi Sébastien,

    I understand you want to pass the negative signal through the switch. As most analog switches are rail-to-rail and pass a complete range of voltages from GND (or negative power supply rail, if applicable) to the positive supply rail, if you want to pass negative voltages you will need a device with a negative supply rail. Please see this list of dual-supply switches in your configuration from the online product selection tool.

    Alternatively, TI has a few single supply devices capable of passing negative voltages, such as TS5A22362. This device will pass signals from Vcc - 5.5V to Vcc.

    Let me know if either of these solutions would work for you.

    Best regards,
    Kate

  • 0 in reply to Kate Dickson
    Prodigy 90 points

    Could you help me selecting another reference? This chip is also used with a HDS-SDI video. So there is a high bandwidth requirement as well.

    So far, the TMUX1511 fits the need unless we consider this small negative voltage issue.

    I was also wondering if I could use a power inverter to create a -1V and assign it only to the GND pin of the TMUX1511. As we power the device in 3.3V, it'd stiil be in recommanded operating conditions and allow the -300mV f the PAL/NTSC signal.

    BR,

    S/

  • 0 in reply to user5867317
    TI__Expert 5660 points

    Hi Sébastien,

    As you stated, TMUX1511 is a good choice for high bandwidth, but the negative voltage would be beyond recommended operating conditions.

    TI does not have a high-bandwidth, single-supply analog switch that will pass negative signals. As I mentioned earlier, you could attempt to use a dual-supply device, such as TS12A4516 that offers rail-to-rail signal switching and a bandwidth of 464 MHz. 

    Best regards,
    Kate

  • 0 in reply to Kate Dickson
    Prodigy 90 points

    Thanks Kate.

    Could you tell how our case could affect the reliability of the device if we don't fix it. Do you have figures to share on this subject?

    Regards,

    Sébastien

  • 0 in reply to user5867317
    TI__Expert 5660 points

    Hi Sébastien,

    Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability. I don't have any figures or information about this exact case, operating in this boundary condition is beyond recommended operating conditions and functional operation is not implied.

    Best regards,
    Kate