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UCC27614: UCC27614 related inquiries & circuit review

Grady Lee
Genius 4485 points

Part Number: UCC27614

Hi, TI experts

The customer is currently reviewing the use of UCC27614 for N-channel MOSFET drive ON/OFF control

1.MCU GPIO -> TI UCC27614 -> N-channel FET Gate control must be performed.

First of all, if you press and hold the POWER OFF button on the product, the N-channel FET should be turned off, but if you look at the attached circuit diagram, it doesn't seem to be turned off accurately.

Q1) We request a review of the attached circuit for identification of any issues and suggestions for improvement.

Your assistance in assessing potential problems and providing recommendations would be greatly appreciated.

Q2) Is it possible to control ON/OFF of N-channel FET using UCC27614?

For reference, the function control configuration diagram is as follows.

[Function control diagram]

Please check. Thank you.

  • 0
    TI__Genius 11810 points

    Hi Grady,

    The UCC27614 will pull out to VDD when on, and pull to GND when off. 

    This setup essentially makes a voltage divider, where 4.7K is in parallel with R5 when a high signal is sent, and in parallel with R6 when the low signal is sent. This results in a gate voltage of 17.2V when high, and 11.4V when low. I simulated this and got the same result. By removing that voltage divider in simulation, the FET was able to be turned off.

    However, the main problem (for Q2) is the source voltage. The FET is only on when Vgs is > Vth. UCC27614 is a low-side gate driver, intended to be used to drive a FET with a source referenced to GND. This is a high-side switch, and the UCC27614 does not have any level-shifting ability to adjust for the source voltage not being 0V.

    Here are three options:

    1. Swap the positions of the heating wire and FETs to make it a low-side switch.
    2. Use a PMOS FET as a high-side FET
    3. Use a high-side switch product. 

    Thanks,

    Alex M.

  • 0 in reply to Alexander Mazany
    Genius 4485 points

    Hi, Alex

    Thank you for reply.

    Is there a device you can recommend as a high side switch?

  • 0 in reply to Grady Lee
    TI__Expert 8568 points

    Hi Grady,

    Alex is currently OoO and will get back to you before end of this week.

    Best,

    Pratik

  • 0 in reply to Pratik Adibatla
    TI__Genius 11810 points

    Hi Grady,

    Sorry for the delay. I would direct your question to the team behind those products. 

    I can send this thread to that team.

    Thanks,

    Alex M.

  • +1 in reply to Alexander Mazany
    TI__Genius 16205 points

    Hi Grady, 

    What is the PWM frequency of this application? Our high side switches are not meant for PWM applications higher than 2kHz. 

    If f≤2kHz, we have the following single channel devices (linked) capable of handling 24V and 2.5A: options

    Our new TPS281C100 could be a good fit. Please let me know if you have any questions about the device.

    Best Regards, 

    Elizabeth