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DS26F32MQML-SP: Maximum Output Voltage

Errol Leon6
Expert 5830 points
Part Number: DS26F32MQML-SP

Hello team,

My customer designing with DS26F32MQML-SP and has a question/concern on the maximum output voltage. In page 4 of the datasheet the minimum Voh is specified to be 2.5V (with a supply of 4.5V), but does not show a max value. Is it correct to assume that the max value would be the whatever VCC is? Is there a way to limit the max output so that it doesn’t exceed 3.6V?

Thank you in advance for your support!

Errol

  • 0
    TI__Guru 62910 points

    Hi Errol,

    The outputs use a push-pull output stage, so a maximum VOH value of VCC is implied.  In reality there will be some voltage drop (especially if there are significant load currents, since the high-side driver would have non-zero resistance), but if you wanted to ensure that the voltage does not exceed 3.6 V the safest solution would be to try to limit it externally.  A couple options to consider would be a dedicated level translator IC or use of a blocking diode in series with the receiver output so that it is able to pull low but high voltages would not pass.  (The lower-voltage device's input could then be pulled up externally to its own IO rail.)

    Regards,
    Max

  • 0 in reply to Max Robertson
    TI__Expert 5830 points

    Thank you Max!

    Do you have any more information about the minimum voh with different load currents? The datasheet calls out a minimum Voh of 2.5V with an Ioh of -440uA.

    This minimum Voh is closer to what the customer would expect with a few milliamp load. Can you shed any light on this?

    Thank you for the support on this!

    Best regards,

    Errol

  • 0 in reply to Errol Leon6
    TI__Guru 62910 points

    Hi Errol,

    I understand the concern.  I'm checking into what further data may be available.  I'll get back to you tomorrow.

    Regards,
    Max

  • 0 in reply to Max Robertson
    TI__Guru 62910 points

    Errol,

    I was able to locate some test data on this.  Even at lower currents there is a somewhat large drop from VCC to VOH due to a blocking diode in the high-side driver.  This causes a drop of about 1.5 V at 25 C and tends to reduce as the temperature increases.  Beyond that, there is some load-dependent drop due to the output resistance of the driver (nominally about 80 Ohms at 25 C).  You may be able to constrain the voltage to within 3.6 V with the right loading, then, although it would require some validation of the solution on the customer's side.

    Regards,
    Max