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LM5021-Q1: CS DISABLE

Chun Hung Chen
Intellectual 590 points
Part Number: LM5021-Q1
Other Parts Discussed in Thread: LM5021, UCC35706, UCC35705, UCC25706, UCC25705, UC3525A, UCC27517

Hi TI Team

I'd like to know the CS function of LM5021-Q1.

Could I disable this function?

I need a PWM IC could work on voltage mode without peak current mode.

Thanks

  • 0
    TI__Mastermind 28990 points

    Hello Chun Hung,

    Thank you for your interest in the LM5021 PWM controller. 

    This device is designed specifically as a peak-current mode controller and cannot be easily adapted to voltage-mode.

    Instead May I suggest for you to consider one of these two voltage-mode controller options:

    UCC25705/UCC35705 are more suited to DC-DC conversion, whereas UCC25706/UCC35706 are suited for off-line conversion.
    The "35" device parameters are guaranteed over 0C to 70C junction temperature range, while the "25" devices are guaranteed from -40C to +85C.

    I hope one of these can satisfy your requirements.

    Regard,
    Ulrich

  • 0 in reply to Ulrich Goerke
    Intellectual 590 points

    Hi Ulrich

    Can I ask you something about two output (like UC3525A or LM2524D) combine together?

    I don't know how to do it. I need a PWM IC could work on CCM & SYNC.

    So, I want to combine the two output of UC3525A.

    The two outputs are the same but there is a 180-degree phase shift between them. 
    I think its duty could achieve 98%, isn't it?

    Thanks

  • 0 in reply to Chun Hung Chen
    TI__Mastermind 28990 points

    Hello Chun Hung,

    I am not an expert concerning the UCC3525A controller, but I do have an idea that might work:
    Connect a 1K resistor in series with each OUTPUTA and OUTPUTB, then connect the other end of both 1K resistors to the input of a single gate-driver IC.  That should result in ~98% duty cycle at the driver input.   Since the center-point voltage will be 1/2 of the OUTPUTx voltage, I think you would need TTL-type input for the gate-driver IC.

    I suggest UCC27517 or similar driver.  Or, search for other low-side driver possibilities here: http://www.ti.com/power-management/gate-drivers/low-side-drivers/overview.html 

    I will also ask some colleagues more familiar with this part to consider your question.

    Regards,
    Ulrich