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TPSM84824: Use it as a converter + power MOSFET

Jingwen Zhu
Prodigy 30 points
Part Number: TPSM84824

Hi team,

I'm planning to use TPSM84824 as a DC converter and power MOSFET for a LED circuit design. Can I switch the LEDs off by pulling down the EN pin on TPSM84824? I've tested it on the evk and it works. However, I would like to know if this usage is recommended.

Thanks,

Jingwen

  • 0
    TI__Genius 14455 points

    Hi Jingwen,

        When you mention Power MOSFET, are you referring to the internal MOSFET of the converter or do you have any additional circuitry?

    There is nothing wrong with pulling the EN pin down frequently. But nevertheless, can you please draw the circuit quickly and share it so that we can give feedback?

    Regards,

    Gerold

  • 0 in reply to Gerold Dhanabalan - Online Design Tools
    Prodigy 30 points

    I meant using the internal MOSFET. I'm hoping to pull the EN pin down to "turn off" the LEDs. In the schematic below, I'm planning to use R1 to pull down the EN pin, to set it as normal off. Connecting 8V_EN pin to a GPIO to toggle the LEDs. Does it work? Should I add an additional circuitry to achieve the toggle function?

  • 0 in reply to Jingwen Zhu
    TI__Genius 14455 points

    Hi Jingwen,

          When the EN pin turns off, you would want Vout to be discharged to prevent the LEDs from turning off. If the output capacitance holds the voltage, then the LEDs will not turn off even though EN pin is turned off. Also, typically the brightness of the LED is a function of the LED current. So driving LEDs with a constant voltage source can result in varying brightness across different designs when manufactured. Typically, constant current sources are used for driving LEDs.

    Also the frequency of the EN pin turn off should be low enough - turning it on/off too fast, will not give enough time for Vout to discharge as well.

    Just things to keep in mind when you are designing. 

    Regards,

    Gerold