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Original question:

[FAQ] TPS23731: Vout setting on diode rectification and primary-side regulation (affect by VFCP)

TPS23731: How to activate CP pin

Shuhei Goto
Expert 4890 points
Part Number: TPS23731

Hi team,

I have a question about CP pin.

[FAQ] TPS23731: Vout setting on diode rectification and primary-side regulation (affect by VFCP)

In this thread, 

The explanation seems to be that the CP pin is recommended for PSR and activated by diode rectification.

Is there a way to function the CP pin without connecting the PSRS pin to AGND, please teach me.

Best regards,

Goto

  • +1
    TI__Mastermind 37071 points

    Hi Goto,

    Thanks for reaching out!

    For PSRS pin configuration:

    PSRS open: when sec side is sync FET and uses PSR

    PSRS tied to AGND: when sec side is diode, or when uses SSR

    When you are using PSR and sec side is diode rectification, PSRS-AGND will make CP pin work as a diode (anode to AGND). It makes sure the auxiliary cap voltage (C40 in the below example) equals a ratio of Vout (V_C40 = N_AUX/N_SEC * Vout). Then the PSR can refer the C40's voltage to regulate Vout. 

    Best regards,

    Diang