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Original question:

TXS0102-Q1: Input voltage level

TXS0102-Q1: Please confirm output behavior for VIL range 0.15V to Vcc-0.4V

Stephen Thomas
Intellectual 710 points
Part Number: TXS0102-Q1 
If input voltage is between 0.15V and Vcc-0.4V, how status is output?

I'd like to know whether the output is high impedance, undefined, whether it is high or low, or whether it is at an intermediate potential proportional to the input voltage.

I'm not pretty clear with the reply TI has provided for the above question.Is it like ,

Considering one shot time period has been expired and if steady state value of 0.15V to Vcc-0.4V is applied to the input the output voltage will be = UNDEFINED ( there is no guarantee that it will be either high or low) .Please confirm if this statement is correct.

  • 0
    Guru 243220 points

    Each channel is switched with a MOSFET. When the input voltage is below the gate voltage (by more than the MOSFET's threshold voltage), then the transistor switches on, and the output voltage is the input voltage plus the voltage drop over the transistor. (The on-resistance is 20 Ω typical, 250 Ω maximum; in the low state, there is always some current because of the pull-up resistors.)

    When the input voltage is increased above 0.15 V, then the output voltage will increase by the same amount. When the input voltages comes near Vgate − Vthreshold, then the on-resistance increases, and the output voltage will increase even more.

  • 0 in reply to Clemens Ladisch
    TI__Mastermind 42600 points

    Hey Stephen,

    Clemens did a great job covering the functionality of this scenario, but I wanted to relate it to you original question. Since this voltage at the output will shift and there really isn't a good way of knowing what it will be ( there are a few variables he provided that you won't have values for), your statement is pretty accurate as the voltage will be undefined.

  • 0 in reply to Clemens Ladisch
    Intellectual 710 points

    Ok I understand your mentioning about the internal working . But I'm not sure about the Vgate and Vthreshold. I checked datasheet but couldn't find it.Can you please provide me the values for the same?

    And really my situation is like im using this device in I2C lines. So most of the device they specify a VOL=0.4V @3 or 4mA .So what i wanted to understand was that when i provide a 0.4V at input what exactly i can expect at the output since VIL max for this device is specified as 0.15V which is pretty tight.

    So from Clemens reply i understand that it will not be an abrupt jump ( to VCCA or VCCB as i initially thought)  in case of 0.4V at input as long as  Im able to keep the transistor turned ON. So some delta +0.4V i can expect at the output. ( that delta will be the current x Rds ON )

    And i think if you can characterize the device in this voltage range i.e above 0.15V and put a curve in datasheet it will be really helpful (just a suggestion).

    Best Regards
    Stephen

  • 0 in reply to Stephen Thomas
    Guru 243220 points

    TI does not tell, but I would expect Vgate to be VCCA, and Vthreshold to be at most 1 V.