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CSD19532KTT: How to make the circuit output pulsed voltage waveform with MOSFET?

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Replies: 3

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Part Number: CSD19532KTT

Hello, TI engineers !

I am intending to obtain pulsed voltage with MOSFET, and the chooper circuit I designed is as followed. To ensure the MOSFET can be turned on, the Source terminal of the FET is connected to the gate driver GND. The gate-source voltage waveform is effective to drive the MOSFET, which is pulse voltage of 5V with duty 20%. 

The output voltage is obtained from Source and GND of supply voltage Vsup (DC power).

When the output of gate driver is high, the MOSFET is conducting so the Source terminal voltage is equal to Vsup.

But when the output of gate driver is low, the MOSFET is working in switch-off state. Then, the voltage difference between Source terminal and GND of Vsup is not sure because there is no common between the two terminals. 

When suppying pulse control signals to the Vin, the output voltage Vout is always high and equal to Vsup, rather than chopped pulse voltage as intended.

What is the problem of this circuit and what should I do to output pulse voltage?

  • Hi Hongwei,
    Thanks for your interest in TI FETs. I don't understand this circuit. Where is the reference for Vsup? From the circuit diagram, it appears that you're trying to use the FET as a high side switch but the source is tied to GND. In order to use this FET as a high side switch, you will need to drive the gate at least 6V greater than the input voltage. This is because the drain and source voltages are essentially equal when the FET is turned on.

    Best Regards,

    John Wallace

    MOSFET technical information on ti.com here

  • In reply to John Wallace1:

    Hi Hongwei,
    Just following up to see if you have resolved your issue. Please let me know if I can be of further assistance. If not, then I will close this thread tomorrow.

    Best Regards,

    John Wallace

    MOSFET technical information on ti.com here

  • In reply to John Wallace1:

    Hi Hongwei,
    Thanks again for your interest in TI MOSFETs. I am closing out this thread as I have not heard back from you and assume your questions have been answered.

    Best Regards,

    John Wallace

    MOSFET technical information on ti.com here

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