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TPS7A78: SCIN voltage calculation

Part Number: TPS7A78

Hi team,

On the datasheet of TPS7A78, section 7.3.7, I found that the Vscin=4*(Vldo+0.6V)-2.5V, so the Vscin should be around 20V.

But according to the block diagram, SCIN should be the output of half bridge/full bridge rectified voltage from AC input.

If I put a 220VAC/50Hz AC input voltage on AC PIN, what's the Vscin voltage?

Could you please help to provide some calculation for this?

Thanks a lot.

James

  • Hi James,

    Thank you for your interest in TI's new smart AC/DC linear regulator. Just wanted to highlight that you should not directly connect AC supply to AC+ pin. AC supply must be connected in accordance to Typical Schematic on the first page of the datasheet.

    As for CSCIN capacitor size, please refer to section 8.1.4 (Input and Output Capacitors Requirements), for calculating CSCIN cap needed for your application based off your load current by using equations 4 - 7 and knowing the AC supply voltage and frequency. 

    CSCIN capacitor voltage is internally controlled (clamped) when AC supply ( AC input mode) is used to power TPS7A78 device, please refer to section 7.4 (Device Functional Modes) for more details. 

    In addition to the device datasheet, the device's EVM User's Guide provide a good insight for this new and innovated device. 

    Again thanks for your interests and please feel free to post any question/questions you may still have.

    BR,

    Haidar