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UCC2818A-Q1: Formula for Imout(max)

Madhura Gogate
Intellectual 1425 points
Part Number: UCC2818A-Q1

Hello team,

In the formula, we can see three terms being used. Can you please confirm on below"

 

I_IAC@Vin_min – This is the current flowing in the IAC pin at Vin_min peak which can be calculated as Vin_min(rms) * sqrt(2) /R_IAC where, Vin_min(rms) = 85Vrms or 170Vrms (in our case), R_IAC = resistance connected to the IAC pin

 

V_VAOUT(min) – Apparently minimum Voltage amplifier output. Is this the voltage amplifier output for Vdc_link(min) which can be calculated as Vdc_link(min) = Vdc_link(nominal) – Vdc_ripple/2 or something else?

 

V_VFF(min) – The current at IAC pin during Vin(min) peak instant is mirrored with 2:1 ratio into the VFF pin. So, this parameter should be equal to I_VFF*R_VFF = (2*I_IAC)*R_VFF. Is this correct?

Thank you!

Best Regards,

Madhura Gogate

  • 0
    TI__Genius 10655 points

    Hi Madhura,

    I'm having trouble finding some of the terms you reference, so it's difficult to verify your assumptions. From what I can discern:

    1. Your assumption on I_IAC(Vin_min) appears correct.

    2. V_VAOUT(min), Please clarify what you mean by Vdc_link.  Also, where is V_VAOUT(min) used?

    3. V_VFF(min) = 1.4V (dictated by internal circuit constraints).  V_VFF is RMS, not peak and is ~ R_VFF*(I_IAC/2)

    Are these references from the datasheet or another app note?

    Also, if you can point me to specific equation numbers, I can have a better idea of the context and can help you more.

    If it helps, you can reference the MathCAD tool from the non-Q1 version of this product: https://www.ti.com/lit/zip/sluc092

    Regards,

    Ray

  • 0 in reply to Ray DiCecco
    TI__Genius 10655 points

    Hi Madhura,

    Since it's been over three weeks since our last correspondence, I assume you determined the wrong part number was entered in the E2E request and your question was ultimately answered. If your question was not resolved, please submit a new E2E. Please be sure to verify the correct part number. 

    Regards,

    Ray