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TPS63000EVM-148: TPS63000EVM Output noise Question.

Bob Lee62837
Mastermind 7230 points
Part Number: TPS63000EVM-148
Other Parts Discussed in Thread: TPS63000

Dear suppormember,

I measured the output noise of TPS63000EVM.

I have a question about output noize at TPS63000EVM.


From measurement of spectrum analyzer
① It can be confirmed that it is growing at the time of down conversion
(high input voltage condition Vin=5.25V).

② It seems that the noise floor is rising at no load.

Q1.
What are the reasons for ①and ②？

Q2.
Switching noise extends to the 800 MHz band.
Is there countermeasure against noise in the 800MHz band?


I attached a waveform.
Could you check it?


<Specification condition>
Vin: 1.8 to 5.25 V
Vout: 3.8 V
Iout: 0 to 300 mA (max)


Best regard.
Bob Lee.

TPS63000_Question_180314.pdf

  • 0
    TI__Expert 5425 points
    The EVM has not been designed for such measurements. From my point of view most of your observations are related to the test setup. If you want accurate and meaningful results I think you need to design a testboard supporting RF measurements.

    The switching frequency of the TPS63000 is between 1.25MHz and 1.5MHz. You can find that information in the datasheet. The rise and fall times of the switching edges is in the range of a few ns, which means the device is not capable to generate a signal at 800MHz.
    You may find resonant frequencies in this range on the PCB or even in your probe connection. For example for a resonance at 800MHz you would need 0.7nH inductance together with the 56pF which you are using in your handmade probe to block the DC voltage. The inductance of the GND loop in your probe could be in this range.