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CSD18543Q3A: Amplify 1MHz signal with push-pull circuit

zabbza
Prodigy 140 points
Part Number: CSD18543Q3A
Other Parts Discussed in Thread: UCC27284, DRV8870, TMUX7221

Tool/software:

Hello,

 I try to design a push pull circuit to amplify 1MHz 3 VDC input signal  to 1MHz 50VDC signal. Output current is maxsimum 100mA.

Signal is square wave.

is there any fault or any suggestion?

Best Regards.

  • 0
    TI__Mastermind 37950 points

    Hello zabbza,

    Thanks for the inquiry. I think your push-pull arrangement should work. The pull up resistor value of 100kΩ is probably too large. Turn-on of the NMOS and turn-off of the PMOS will be slowed down by the large pull up resistor. Also, PMOS FETs switch slower than NMOS due to lower carrier mobility for the same on resistance. TI NMOS goes to 100V max and PMOS only goes to -20V max. Please let me know if I can assist you further.

    Best Regards,

    John Wallace

    TI FET Applications

  • 0 in reply to John Wallace1
    Prodigy 140 points

    Hello John,

    Is there any IC solution ? or any improvement to drive FETs high speed?

    Above pic there is one more nmos for high side, what is its purpose?

    Best Regards

  • 0 in reply to zabbza
    TI__Mastermind 37950 points

    Hi zabbza,

    Yes, you can use a gate driver IC to drive the FETs. The device you have shown is a low side driver. The added NMOS looks like it provides a short pulse of current to turn on the FET fast. You might consider a half-bridge driver to drive 2 N-channel MOSFETs. I am going to move this thread to the gate drivers applications team to assist you.

    Thanks,

    John

  • 0 in reply to John Wallace1
    TI__Genius 14145 points

    Hey Zabbza,

    I am the Applications Engineer supporting our gate drivers. As John has mentioned, you may want to consider a half-bridge gate driver such as the UCC27284 to drive two NMOS FETs in a configuration as seen below:

    Can you share more about your output load, circuit topology, and end equipment you are working with?

    Let me know if you have any questions.

    Thank you,

    William Moore

  • 0 in reply to William Moore
    Prodigy 140 points

    Hello William,

    Thank you for your kindly answer.

    The load is piezo.  The frequency is 1MHz.

    Please share your suggestions.

    Best Regards.

  • 0 in reply to zabbza
    TI__Genius 14145 points

    Hey Zabbza,

    The UCC27284 should be a good potential candidate for this system then. It is a 120V rated half-bridge driver with 3A of gate drive current to drive 2 NMOS FETs in a half-bridge configuration.

    Thank you,

    William Moore

  • 0 in reply to William Moore
    Prodigy 140 points

    Hi William,

    May The Cap which is between "HB" and "HS" distorted 1MHz output signal?

    There are extra diodes in datasheet typical application circuit.

    What is their purpose? may you give some details?

    In below document,

    https://www.ti.com/lit/an/slaa780a/slaa780a.pdf?ts=1718267498729&ref_url=https%253A%252F%252Fwww.google.com%252F

    DRV8870 drive piezo without mosfets but maxiumum frequency is 200kHz.

    Is there any other IC which is capable 52VDC and 1Mhz signal.

    Or May UCC27284 used without mosfets like DRV8870.

    Best Regards.

  • 0 in reply to zabbza
    TI__Mastermind 23015 points

    Hello Zabbza,

    William is out of the office until next week, I will look to address your recent questions. I am not sure about the 1st question, may the cap which it between HB and HS distorted 1MHz output signal? I am not sure what that is asking, can you clarify if you are worried about noise between HB and HS? 

    There are diodes shown in the typical application on the gate drive circuit that 1) provide a path to have a lower turn off gate resistance than turn on gate resistance and 2) clamp the driver output to the ground reference.

    The HPD product line that I support does not have any drivers rated to 52V VDD and driver output voltages. the DRV products are likely your best choice for direct drive.

    The UCC27284 driver is intended to drive N channel Mosfets in a HB configuration. The drivers can support high peak currents to charge and discharge the Qg of the Mosfets but are not rated for high average current. We would not recommend the UCC27284 for direct drive unless the average current is very low.

    Regards,

  • 0 in reply to Richard Herring
    Prodigy 140 points

    Hello Richard,

    "if you are worried about noise between HB and HS? "

    Yes worried about noise.

    "We would not recommend the UCC27284 for direct drive unless the average current is very low."

    Average current is maximum 50mA. Is UCC27284 capable for direct drive when current is 50mA?

    if it is capable for direct drive how it may connect to piezo cell directly?

    Best Regards

  • 0 in reply to zabbza
    TI__Mastermind 23015 points

    Hello Zabbza,

    If the average current is 50mA or less then the driver is likely capable of supporting this average current. Regarding how to drive or connect to the piezo directly, that now becomes an issue. To be able to switch from 0 to the voltage buss input, the driver is set up to drive a low side FET with the FET drain supporting the higher bus voltage. I think you still need the external FETs to achieve the higher voltage peak to peak drive signal. These FETs could be very small devices however.

    Regards,

  • 0 in reply to Richard Herring
    Prodigy 140 points

    Hello Richard,

    Thank you for your answers.

    I have one last question, do you have any suggestion to drive push-pull circuit without any driver IC.

    Best Regards

  • 0 in reply to zabbza
    TI__Expert 5921 points

    Hi Zabbza, it is a holiday in the US this week, so responses will be delayed. Our team will get back to you early next week.

    Regards,

    Daniel

  • 0 in reply to Daniel Norwood
    Prodigy 140 points

    Hello,

    May TMUX7221 is used instead of low side gate driver.

    Max current is about 50mA.

    Best Regards

  • 0 in reply to zabbza
    TI__Genius 14145 points

    Hey Zabbza,

    Richard and myself are Applications Engineers for the gate drivers and so we are not experts to comment on other products. Please create a thread for the TMUX7221 and the team for that product will be able to assist you for if it will work for your application.

    Thank you,

    William Moore