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SN74ABT540: Does VOH(MIN) occur at low temperature?

Kurt Schmidt
Genius 11125 points
Part Number: SN74ABT540

Based on the output structure of ABT logic (bipolar + high-side diode) I assume VOH will increase with increasing temperature. If so, then the VOH(MIN) spec will occur at low temperature.

a) Is this a correct assumption?

b) Do you have any characterization data that would suggest what the tempco is such that we could estimate VOH(MIN) over a limited temperature range (0C - 85C)?

c) Do you have any data to suggest what VOH(MAX) is?

Thank you, Kurt

  • 0
    TI__Mastermind 46045 points

    Hey Kurt,

    Unfortunately, there is no data we have to confirm your assumption or to help with estimations. My expectation, the Voh will see more of a shift from slight current shifts rather than temp changes. We can see this by comparing the specs for the mil version with extended temp range, the 3 mA case share the same spec which would indicate similar performance at the same current out.

  • 0 in reply to Dylan Hubbard
    TI__Genius 11125 points

    The simplified output structure is a diode in series with a Darlington driven transistor. I know these are very mature parts so there isn't a ton of data. But a look at the output structure suggests Voh will increase with increasing temperature (diode Vf and transistor Vce(sat) usually decrease with increasing temperature, while transistor beta usually increases.)  So the expectation is that Voh will be worst at low temperature. But I don't know everything that is in the actual internal circuitry ...

    Voh will absolutely move with shifting output current. But that does not tell us anything about shift over temperature at a given current (say 3mA which is the current the data sheet sets it specifications at. I'm not looking for absolute values just the behavioral trend.

  • 0 in reply to Kurt Schmidt
    TI__Mastermind 46045 points

    Hey Kurt,

    Your understanding is correct here, I just wish I had some data to provide to really solidify your assertion and provide you a better look at the behavioral trend. 

    I did dig up a characterization report as well an app note covering ABT design (linked below) that I hope will help provide any additional details.