ADM2682E VISOOUT Response

Hi

I'm a DFAE in Japan. Our customer evaluates ADM2682E and gives us a question. When DE switches from L to H, an undershoot of about 0.1V occurs in VISOOUT, and when switching from H to L, an overshoot of about 0.1V occurs. When DE is L, VISOOUT is 3.4V, and when H, it is 3.36V. Only the Typ value of 3.3V is described in the DS, and it is not possible to judge whether this voltage change is the correct operation. Could you please help me?

Regards,

Hiroyuki

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  • +1
    •  Analog Employees 
    on Mar 30, 2021 12:49 PM

    Hi Hiroyuki, 

    This is expected behavior for the ADM2682E and is caused by the step change in load when the DE switches to/from L and H, and by the dynamic load regulation of the isolated DCDC converter in the ADM2682E. 

    When the DE pin is low, the ADM2682E driver is off and the current drawn from the VISOOUT pin is a few mA's. 

    When the DE pin is high, the ADM2682E driver is enabled, and the current drawn from the VISOOUT pin rises to up to 40mA, depending on the termination resistors across the Y and Z pins, and the data rate applied to the TxD input.

    This step change in the current drawn from the VISOOUT pin causes a voltage overshoot (during HL transition on DE) and undershoot (during LH transition on DE). This is expected behavior for any voltage regulator.  

    The plot shown below shows the load regulation of the DCDC converter used in the ADM2682E, for a step increase in current from ~4mA to ~36mA. This correlates pretty closely the 0.1V undershoot and overshoot you have observed.  

    Regards,

    Neil 

Reply
  • +1
    •  Analog Employees 
    on Mar 30, 2021 12:49 PM

    Hi Hiroyuki, 

    This is expected behavior for the ADM2682E and is caused by the step change in load when the DE switches to/from L and H, and by the dynamic load regulation of the isolated DCDC converter in the ADM2682E. 

    When the DE pin is low, the ADM2682E driver is off and the current drawn from the VISOOUT pin is a few mA's. 

    When the DE pin is high, the ADM2682E driver is enabled, and the current drawn from the VISOOUT pin rises to up to 40mA, depending on the termination resistors across the Y and Z pins, and the data rate applied to the TxD input.

    This step change in the current drawn from the VISOOUT pin causes a voltage overshoot (during HL transition on DE) and undershoot (during LH transition on DE). This is expected behavior for any voltage regulator.  

    The plot shown below shows the load regulation of the DCDC converter used in the ADM2682E, for a step increase in current from ~4mA to ~36mA. This correlates pretty closely the 0.1V undershoot and overshoot you have observed.  

    Regards,

    Neil 

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