• State TI Thinks Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 64 subscribers
  • Views 811 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

UCC20520: Half Bridge Gate Driver (similar to UCC20520) with capability of negative bias

Michael Moitzi
Prodigy 60 points
Part Number: UCC20520
Other Parts Discussed in Thread: LM5110

Hi,

I am looking for a half bridge gate driver with the possibility of negative bias. I am thinking of something like a combination of UCC20520 and LM5110. Is there a part available, which suits my requirements? Currently I am using the LM5110 but unfortunately I have a lot of ringing on the outputs of the driver which causes distortions on the output of the half bridge at short on times. I am hoping that a part similar to UCC20520 provides more stable outputs.

For further specification here are some details about my requirements:

  • ton = 20ns – 20µs
  • toff = 500µs – 1ms
  • duty cycle min = 0.002%
  • duty cycle max = 4%
  • Vvarneg = -1.5V – -5V


The reason why I need negative bias is due to the negative voltage across the half bridge I need a negative voltage to fully turn on the FET. For further information I have attached a simplified schematic.


 

Best regards,
Michael

  • 0
    TI__Mastermind 31510 points

    Hi Michael,

    I want to make sure I understand: you are attempting to drive a square wave with low level +3.3V and high level +5V, to the gates of a half-bridge with top drain connected to 0V and bottom source connected to an adjustable negative voltage between -1.5V and -5V? The level-shift should not be a problem for UCC20520, provided there are isolated or level-shifted supplies available for the outputs. However, all TI isolated gate drivers have UVLO threshold of 5V or greater. I don't think there are any TI gate drivers designed to produce short, low-amplitude pulses like this. Please let me know if I am understanding the application correctly, or else let me know the characteristics of the signal applied to the gates of the bridge in more detail, and I will provide further assistance.

    Regards,

  • 0 in reply to Derek Payne
    Prodigy 60 points

    Hi Derek,

    Thank you for your answer.

    Yes you (kind of, maybe my schematic is a bit misleading) understood it correctly – I want a square wave with low level -5V and high level +3.3V. But for high level +5V should work as well. It should just switch the voltage connected to the bridge.

    The signal to the gates of the bridge should be sufficient to switch the voltage Vvarneg (which is, as you understood correctly, between -1.5V and -5V). That means that the characteristics of the signal applied to the gates are just definded by the pulse width (which is between 20ns – 20µs). The half bridge is used to implement a simple pulse generator.

    I hope that this answers your questions.

    Best regards,

    Michael

  • 0 in reply to Michael Moitzi
    TI__Mastermind 31510 points
    Hi Michael,

    Thanks for the clarification. Since the UCC20520 UVLO threshold is set at 8.5V typical, using -5V and +3.3V does not provide sufficient voltage to activate UCC20520. I recommend -5V and 5V since this combination exceeds the UVLO threshold.

    UCC20520 can function with the control side referenced to GND and the output VSSx pins referenced to any voltage within the isolation ratings. Unless there is a specific feature from LM5110 that is required but not replicated by UCC20520, I think using UCC20520 alone should be sufficient for this application.

    Regards,