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TPSF12C3-Q1: How do we select CSENSE and CINJ value?

Yoshiki Ochi
Genius 9365 points
Part Number: TPSF12C3-Q1

Hi team, 

  1. How do we decide CSENSE and CINJ value? 
  2. How do we decide RG, CG1, and CG2 value? 
  3. What is GAEF shown in datasheet equation (1)? Which parameter should we refer to on quickstart calculator?

Regards,
Ochi

  • 0
    TI__Guru 72992 points

    Hi Ochi-san,

    1. Csense is typically 680pF. This gives a reasonable AC amplitude at the sense pins and sufficient attenuation of line ripple to the INJ pin. Cinj is typically 4.7nF but can be higher as well, e.g. 10nF, 22nF (depends also on the allowable leakage current spec).

    2. Rg, Cg1 and Cg2 set the gain and are typically not modified.

    3. Gaef is the AEF loop gain. It is plotted in the quickstart file.

    Regards,

    Tim

  • 0 in reply to Timothy Hegarty
    TI__Genius 9365 points

    Hi Tim, 

    Timothy Hegarty said:
    1. Csense is typically 680pF. This gives a reasonable AC amplitude at the sense pins and sufficient attenuation of line ripple to the INJ pin. Cinj is typically 4.7nF but can be higher as well, e.g. 10nF, 22nF (depends also on the allowable leakage current spec).

    4) How do we calaculate AC amplitude at the sense pin using 680pF?

    5) How Cinj leakage current do we estimate for each Cinj value?

    Regards,
    Ochi

  • 0 in reply to Yoshiki Ochi
    TI__Guru 72992 points

    Ochi-san,

    You can use the PSPICE or SIMPLIS models to examine the AC amplitude at the sense pins. The first-stage high-pass filter is the sense cap and a 10kΩ resistor.

    The leakage current at 50Hz or 60Hz is Vac*2*Pi*fac*Cinj. Note, however, that this line-frequency current can flow in the VDD supply and not actually to GND.

    Regards,

    Tim