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tps55010evm-009 repeatability and performance

Wallace Ly
Prodigy 240 points
Other Parts Discussed in Thread: TPS55010

Hi,

I have tested the standard TPS5510evm-009 (no modification) for my customer and have the following data.

Data was acquired from an active load inside SVA lab.

My customer have a question as to component tolerances and environmental parameters.

I tested the EVM at 25C with Vin=5.0V @ 5% tolerance.

Is it okay to expect similar performance at elevated temperatures? 70C, 85C?

While the customer is okay for the output to be out of regulation at 4.4V @ 500mA, he will pass the output to a LDO for a final stage of 3.3V @ 300mA (target).

Is this okay? Please advise.

6.01V @ 0A

4.42V @ 0.5A

4.69V @ 0.3A

4.84V @ 0.2A

4.89V @ 0.16A

Best Regards,

Wallace

  • 0
    TI__Mastermind 35165 points

    Hi Wallace,

    This data looks normal. At heavier loads the output voltage starts dropping due to the voltage drop across the low-side FET, the output schottky diode, and voltage drop across the resistance of the windings of the transformer.

    One thing, do they plan to redesign the circuit to support the 0.5A load? The EVM design as is is for 0.2A. A couple changes may be needed and I recommend following the datasheet equations to check. The excel sheet located in the TPS55010 product page works great to do this.

    Best Regards,
    Anthony

  • 0 in reply to Anthony F
    Prodigy 240 points

    Hi Anthony,

    Thank you. Targeting the 0.5A @ 5V would be preferable but I had a hard time using the calculator with the Wurth inductor called out.

    From the excel calculator the FET current is exceeded beyond what the TPS55010 can do. I tried manipulating the Fsw and to a certain point it helped but I could not the calculator to a stable 5V/0.5A output.

    Could you give me a excel template for 0.5A?

    Best Regards,

    Wallace

  • 0 in reply to Wallace Ly
    TI__Mastermind 35165 points

    It's not an issue with the template but limitations of the IC for a 5V at 0.5A design. It is more optimized for closer to 1W applications while this is 2.5W. To use the same transformer, my first thought is yours to reduce the switching frequency and ignore the Lomax calculation. This calculation is to give best efficiency at full load and is not a hard requirement.

    I tried myself and after tweaking the switching frequency some this might not even be possible with the same transformer because the design is at risk of being limited by the low-side current limit. The best option I see is to reduce the primary regulated voltage from 2.2V. This can be reduced some depending on how much margin you need on the output for the drop out of the LDO.