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DS90LV012A: Output Current

Trenton Reed
Intellectual 2825 points
Part Number: DS90LV012A
Other Parts Discussed in Thread: SN74LVC1G17

Hi Team,

What is the output sink/source current (pin 5 TTL OUT) of DS90LV012A?

Thank you,

TR

  • +1
    Guru 244020 points

    The effective limits are IOH = −0.4 mA, IOL = 2 mA, as these are the test conditions for VOH/VOL.

  • 0 in reply to Clemens Ladisch
    TI__Intellectual 2825 points

    Follow-on question... Can you help me understand why the I_OS (output short circuit current) is -15mA to -100mA but then the output current for Voh/Vol is -0.4mA and 2mA in the test conditions? 

    If the output is shorted then isn't the -15mA to -100mA what our part is designed to sink?

    Trying to figure out why the numbers are vastly different. Customer is trying to level translate the 3.3V output to a 1.8V signal. They used series 150-Ohms and 270-Ohms to GND; they estimated the current was 7mA. This is 27MHz output. Looks pretty good to me. Any issue with their waveform?

  • 0 in reply to Trenton Reed
    Guru 244020 points

    The output has a certain impedance; if you source or sink current, there will be a voltage drop over the output transistor, and the output voltages are no longer at the supply rails. A shorted output does not generate voltages that would allow you to distinguish high and low levels. As long as you source no more than IOH, TI guarantees that the output voltage stays above VOH.

    If you do not care about VOH, then you can try to source more current. But then there are no longer any guarantees about the actual output voltage; the short-circuit current specification shows that the output impedance is somewhere between 33 Ω and 220 Ω.

    How much current should flow through the voltage divider depends on how much parasitic capacitance your circuit has. The waveform looks OK; you might try to increase the resistors to find out when you get problems.

    If you want to translate down without wasting power, use a buffer with overvoltage-tolerant input such as the SN74LVC1G17.