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TPS92660: TPS92660 functiont

user1166673
Prodigy 70 points
Part Number: TPS92660

helleo , I need to drive a laser diode array, total 8 strings , each string voltage about 35V, constant current 2.5A(typical), 3A(max), TPS92660 can be current trimmed by I2C interface, and achieve PWM current, it is good for me. Now I have some questions for TPS92660:

  1. Its Iout ( max )is 5A from TI website . This is buck converter out current, right? The linear regulator max out current?

  2. About the buck converter out current trim, if I set out current is 2.5A, the current change -20% should be 2A, 32 steps from 2.5A to 2A, each step change about 0.6%(about 0.015A); the current change 19.4% should be 2.985A, 32 steps from 2.5A to 2.985A, each step change about 0.6%(about 0.015A); right?

  3. If I parallel 8 stings LD at an output voltage, is that okay? Will there be interference between them?

Do you have any suggestions or good solutions for my application?

  • 0
    TI__Mastermind 25500 points

    Hello,

    Could you let me know what your input voltage will be? Do you need the I2C trim functionality? Is the 2.5A/3A spec per LED string or a total for all 8 in parallel? I might be able to suggest something else if you can give me these answers. But to answer your questions on the 660:

    1. Yes, that is for the buck converter. The linear regulator max current really depends on if the 660 linear gate drive can handle the FET used and how much power dissipation you don't mind burning in the FET. The power could get very high in it very fast as you increase current depending on how much voltage it has to drop to regulate the LED string current.

    2. Yes, that is correct.

    3. It depends on how tight the current accuracy needs to be in each string. It's a common practice so yes in theory you can parallel all 8 strings. But any slight variation in Vf between the strings will cause some slight current mismatch.

    Regards,

    Clint

  • 0 in reply to Clinton Jensen
    Prodigy 70 points

    Hi Clint

    Thanks for you answer.

    my input voltage can be adjust, my initial idea is to 30-40V between the adjustable, it depend on each string voltage. If each string voltage is 35V, how much voltage do you recommend? What is the minimum voltage difference between input and output? Is this value a little more efficient?

    I think I2C trim functionality is best, this feature is integrated into the chip, precision, stability and anti-interference will be better.

    Per led string current is 2.5A/3A,

  • 0 in reply to user1166673
    TI__Mastermind 25500 points

    Hello,

    If you like the I2C and high precision then this is a good device. You may need one for each string or two if each of them needs to be at that current level. Stability is also not an issue with this device. It just requires a cap and will still have fast transient response.

    If your LED string is 35V then I would have an input voltage of at least 40V or so. The 660 doesn't require a ton of headroom, but I would still shoot for at least 5V.

    Regards,

    Clint