ADA4433

Hello Sir/Madam,

I am approaching this forum, because I would like to have some more information regarding the functionality of ADA4433 Video Filter and Amplifier.

1. The datasheet, page 15-16, mentions that the IC has a short to ground protection feature, and it limits the current source/sink up to 60mA. If two inputs are shorted the current source/sink is limited to 50mA. However, the datasheet fails to mention whether in this condition the ADA4433 would stop sourcing/sinking current (for power safe reasons) after a certain time. Is there such a functionality? If so, what is this time? Also what is the power consumption vs short to GND time.

2. I would also like to know more information regarding the current consumption (drawn from the power source) on:

     a) No Load/No Signal condition

         What does No-Load condition entails? Is having an open circuit on only one of the output lines considered a No Load situation?

          It would be helpful to know how the IC determines the absence of the load.

     b) Normal operation i.e. RL = 150 Ohm and with input signal

         what is the current consumption variation in normal operation? It would be great to have minimum and maximum levels indicated.

Thank you in advance for your help!

  • Hi, Ertion Axha.

    These are the answers to your questions.

    1.The condition holds as long as the fault persists. If the part was to turn off the 60 mA after a certain period but the fault still persisted the part would blow up. So, I think you are asking for an impossible “functionality”. If you short the inputs or outputs to GND the current limit is the same at 60 mA.

    2. a) No Load/No Signal condition

             What does No-Load condition entails? Is having an open circuit on only one of the output lines considered a No Load situation?

    No load means both outputs are open circuit.

              It would be helpful to know how the IC determines the absence of the load.

    The IC does not know if there is a load connected or not. The output voltage will force current through the load. If the load is not connected no current.

        b) Normal operation i.e. RL = 150 Ohm and with input signal

            what is the current consumption variation in normal operation? It would be great to have minimum and maximum levels indicated.

    The average current consumption depends on the load resistance and on the average output voltage. It would be unwise for ADI to “guess” what sort of average output voltage will the customer generate, so the maximum levels have to be determined by the user.


    Credit to Zoltan.


    Regards,

    Anna

  • Hi Anna,

    Thank you very much for your reply. I appreciate it.

    1. I agree with you that if the current limiting functionality would be turned off, the IC would blow up. Maybe my question was not formulated properly. I wanted to know if the chip had the functionality to stop supplying/sinking currents at the output (i.e. open circuit the output terminals) after a certain time. This would be a power save functionality in case such faults would persist. Continuously supplying +-60mA of current would be a waste in remote applications with a battery supply.

    2.a From your second answer I see that the IC is able to understand the current flow through he load. What is the mechanism that measures this a current sense on the output lines?

    I am asking because in the datasheet, it is mentioned that at no load/no signal situation, the quiescent current consumption from the power lines is max 18 mA. Is this only because there is no current flow on both differential lines, (thus current requirements are less) or is it because the IC restricts current consumption when detects no load/no signal.

    2.b Thank you for your answer on this. The datasheet mentions that the average linear Output Current on RL = 150 Ohms, Vs = 3.3V, V-in = 0.5V, Ta = 25 C is +- 29mA. How can I estimate or do an approximated but educated 'guess' of the supply current requirements of this IC at these conditions?

    Thank you in advance.

    Regards,

    Ertion

  • Hello Anna,

    I would also like to add to question 2.b. What would be the current consumption if one output is open circuit, in the same conditions. I would expect it to half, but I would appreciate your comment on this.

    Kind regards,

    Ertion

  • Hi, Ertion.

    1. There's no way that the part will stop from sinking/sourcing current. The best way for this is to add some protection circuit before the ADA4433-1.

    2. Current is like water. If there is no path (like load resistor), the water won't flow.

    2.b The current would be half on the open circuit because the half of the current will flow through the output with load.

    3. This depends in so many factors. First is the load: the lower it is the more current it consumes. Second is the voltage: the higher it is the higher the current. Third is the adjacent circuits: the more the components the more the current. Fourth is the temperature: the higher the temperature the higher the current. And other factors like frequency etc. ADI can't predict all the effects of these factors so ADI provide typical or tested values which the customer could refer to.

    Regards,

    Anna

  • This question has been assumed as answered either offline via email or with a multi-part answer. This question has now been closed out. If you have an inquiry related to this topic please post a new question in the applicable product forum.

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    EZ Admin