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LM5122: Device Suggestion

Jagannathan Rajan
Prodigy 140 points
Part Number: LM5122
Other Parts Discussed in Thread: LM51772

Tool/software:

Hi team,

We are designing a high-power LED flash system. The LEDs require 500W peak power for a 1ms pulse, with a flash frequency ranging from 1Hz to 67Hz. We plan to use a MOSFET to switch the LEDs and are looking for a suitable regulator to supply this power. Using two drivers in parallel is acceptable if needed.

The output requirements are either 50V at 10A or 100V at 5A, with an input voltage range of 9V to 36V. We are currently evaluating the LM5122 and LM5172 using Webench.

Is this design feasible? Could you recommend any suitable power devices or alternative approaches for this application?

LM5122 - webench.ti.com/.../SDP.cgi

LM5172 - webench.ti.com/.../SDP.cgi

Thanks,

Jagan

  • +1
    TI__Mastermind 30080 points

    Hi Jagan,

    Thanks for using the e2e forum.
    Is LM5172 the correct device name, or do you mean LM51772? (I did not find LM5172)

    LM5122 works fine for the output case of 50V, 10A, but the output voltage in the seconds case (100V, 5A) might be too high.
    The LM5122 has an abs max value of 105V at the SW pin. This means, if there are any overshoots or ringing on the SW, the device will break.

    Unfortunately, I do not know any other synchronous devices from our portfolio that support higher output voltages.
    An alternative would be to do a asynchronous implementation. Meaning to replace the high side FET with a diode and short the SW pin to GND.
    This avoids the problem with the abs max restrictions.
    The disadvantage of this implementation is that the losses at the diode will be higher for these power levels.
    (Multi phase implementation does still work with this approach)

    Best regards,
    Niklas