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ALM2403-Q1: Inquiry on loss calculation formula in the data sheet

Paul Chang
Prodigy 30 points
Part Number: ALM2403-Q1

Tool/software:

Hi TI Teams

I would like to ask,

Since the Rsolver we are using is for AC signals,

But the calculation formula used in the document is the calculation formula used for DC signals

Because the AC formula is used under the condition

We want to know If we are using AC signal directly, can we ignore the condition and use POPA (PEAK⎽AC) directly to calculate the loss?

Thanks

  • 0
    TI__Genius 10836 points

    Hi Paul,

    Yes, you are correct. If you are AC coupling the resolver, you will have no DC current path passing into the resolver. Even still, you may have the feedback components which offer a DC path to GND. These feedback and gain resistors can appear as an equivalent RL to the amplifier depending on the circuit configuration.

    Additionally, the quiescent current of the device will act as a constant power loss to the amplifier. 

    It is likely that the DC power loss for an AC coupled resolver will be much less than the AC power loss, but it is still a good idea to run the calculation to verify this is the case. 

    Please let me know if you need any help with calculating power dissipation for the ALM device. 

    Thanks,

    Jacob

  • 0 in reply to Jacob Nogaj
    Prodigy 30 points

    Hi Jacob

    Thanks for answer

    But I have another question

    If my Vcc is 20V，Vout is 7Vrms so peak is about 20V

    Can the AC formula be used in this situation as well?

    Thanks

  • 0 in reply to Paul Chang
    TI__Genius 10836 points

    Hey Paul,

    Yes, 20V supply is fine for LM2403-Q1. You can use the AC formula for the situation above.

    Output voltage will depend on the load (resolver) and circuit design. 20V Pk will probably not be possible depending on the peak load current seen by the system. 

    Do you have a circuit design in mind?

    Thanks,

    Jacob

  • 0 in reply to Jacob Nogaj
    Prodigy 30 points

    Hi Jacob

    Thanks for answer

    Yes, I have a direction in mind.

    Thanks

  • 0 in reply to Paul Chang
    TI__Genius 10836 points

    Hey Paul,

    Great to hear! Please let me know if you have any questions on the design. I am happy to assist as needed. 

    Best,

    Jacob