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TPS92515HV: PWM Frequency

WEI LI5
Prodigy 60 points
Part Number: TPS92515HV
Other Parts Discussed in Thread: LM3409HV, LM3409, TPS92515,

Hi,

We are using LM3409HV in our product, it is very good, now I have a new project. I want to try this one, because it is nice to integrate a switching MOSFET for lower cost, and I have one question: Is it able to support 20KHz PWM Frequency at 3-5% lowest duty cycle, which LM3409HV can easliy meet it, thanks.

Regards,

Wei

  • 0
    TI__Mastermind 25500 points

    Hello Wei,

    Aside from some minor differences the TPS92515 is essentially the integrated version of the LM3409. So whatever capabilities the LM3409 has that you like, including high frequency PWM dimming, the TPS92515 can also do it.

    Keep in mind however that depending on your operating points (Vin, Vout, ILED, etc...) you will need to consider thermals with the 515 since it is integrated.

    Regards,

    Clint

  • 0
    Prodigy 60 points

    Hi,

    Sounds Great! Can I get 2 evaluation board samples (p/n: TPS92515HVEVM-749) for checking? Many thanks.

    Regards,

    Wei

  • 0 in reply to WEI LI5
    TI__Mastermind 25500 points

    Hello Wei,

    Unfortunately I do not have any of those EVMs. But they are available on the web. You can also refer to its user's guide for some dimming information. You can also check the TI/Reference designs at:

    Those designs have a good bit of high frequency dimming data as well.

    Regards,

    Clint

  • 0
    Prodigy 60 points

    Hi,

    How about the Turn-On delay between PWM and the output current? Is TPS92515 shorter than LM3409 in general, assuming they are running at the similar condition, e.g. same input voltage and same output current? How can we reduce the delay of LM3409, except by using external parallel FET shunt dimming method, thanks.

    Regards,

    Wei

  • 0 in reply to WEI LI5
    TI__Mastermind 25500 points

    The inherent IC delays are about the same, 40ns to 50ns or so. It looks like the 09 has slightly less delay. But the current rise time will be the same given the same conditions and component values.

    Regards,

    Clint

  • 0 in reply to Clinton Jensen
    Prodigy 60 points

    Hi Clinton,

    It shows about 3.5us rising time on Figture 7 of AN-1953 LM3409HV Evaluation Board, which will effect the dimming performance at very low dimming level, is there way to reduce it? Our target is about 2us, by using internal swithch. BTW, do you have any local FAE in bay area, thanks.

    Regards,

    Wei

  • 0 in reply to WEI LI5
    TI__Mastermind 25500 points

    Hello Wei,

    I'm checking about an FAE in the bay area but I have not heard back yet. As far as the 3.5us rise time, that is a function of the input voltage, the LED stack voltage, and the inductor value. It's just v=Ldi/dt. So that rise time (dt) is dt = (L*di)/(Vin-Vled). So if you change the inductor value from 33uH to 15uH you will get approximately half the current rise time. I will let you know if/when I find out about a bay area FAE.

    Best regards,

    Clint