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ad8561 model seems to be incorrect in LTspice

Category: Datasheet/Specs
Product Number: AD8561
Software Version: ltspice

Hi the ad8561 model in LTspice seems to be incorrect. see the picture i attached. the schematic has a vref of (2.5V) at the (+) input and i am suppling a ramp input at (-) . the output at  pin 7(green) should go low when the input reaches 2.5v but it looks like its going high(green). i am not sure if this is correct. also the same goes for output at pin 8 (blue). 

  • Hi naahm2,

    Based on your circuit, the pulse signal is in the negative input and the threshold voltage = 2.5V is in the positive input which then inverts your output. Therefore, the response is correct.
    If you do not want to invert your output, the pulse signal should be in the positive input and the threshold voltage = 2.5V should be in the negative input.

    Hope it helps.

    Best Regards,
    Sham

  • the ramp signal is in the negative input and vref is on the positive input.  the pulse signal in green is the output from pin 7 and the blue signal is from pin 8. i don't think this is correct. The signal injection is at the inverting input (pin 3), so the sense of the non-inverting output (pin 7) should be opposite the input signal. 

  • I agree; the model (more precisley, the .asy) is wrong. The output pins are swapped.

    In the .asy, right klicking on OUT (right pin order but wrong label):

    Right click on OUT_BAR (right pin order but wrong label):

  • hi  ,

    I've checked this with my LTspice and the response seems to be different from yours, I have to agree with   that the output Q and Q' is originally inverted when it was first uploaded in our library.

    I've checked it already and this was already address last March 4, 2024. (You can check the Model Change Log under Help)

    Here is also my version of your circuit showing that the expected response is met.

    Kindly update your Model Library under Tools>Update Components.

    Please also make sure that you are using our latest LTspice Version 24. Slight smile

    Thank you and Best Regards,

    Earl

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