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AMC1300: Output noise at around 620kHz

Part Number: AMC1300
Other Parts Discussed in Thread: AMC1200, AMC1200EVM, SN6501

Hi all, 
My customer has evaluated AMC1300 on AMC1200EVM  by replacing AMC1200 at U2 position with AMC1300.
And they found the noise at around 620kHz.
In case of AMC1200, such a noise is not observed.

AMC1300 has an 4th-Order active LPF at output stage.So that I think that such noise is not observed.

Is the appearance of this noise the characteristic of AMC1300?
Is it possible to reduce this noise by setting filter etc.?




  • Hello,

    Can you confirm if you're using the SN6501 circuit on the EVM to power the VDD1 side of the AMC1300?  If so, try the results again using another bench supply and let us know the results.  The AMC1300 has much lower output noise than the AMC1200 so this is likely a configuration or setup related behavior and if you didn't clean the board very carefully that could be causing effects as well.

  •  Colin-san,

    Thanks for your suggestion.

    My customer tried to use a clean power for VDD2 and removed SN6501 for reducing the noise from EVM.
    But the noise was not improved as below.
    What is the cause of this noise?


  • Hi Toshi,

    It looks like you are measuring OUTP and OUTN in a single ended manor. Can you look at the outputs with a differential probe and let us know if the situation improves?
  • Hi Tom-san,

    Since my customer did not have a differential probe for this measurement, they used two probes and observed using the MATH function of the oscilloscope. The noise is not improved.

    There is a possibility that the adjustment of the two probes was not enough for the customer's measurement, but can I ask you to confirm if the phenomenon of the customer is reproduced?

    Best regards,
  • Hi Toshi,

    don't directly touch the output of AMC1300 with the scope probe. Mount a 50R resistor to each output and connect the scope probe behind these resistors. By this the capacitive load of scope probe is isolated from the output of AMC1300 and the chip can work stably. And I would take a 10:1 scope probe.

  • Note:  Post updated due to measurement setup issues interfering with the previous results.


    We tested the AMC1300 EVM in the lab today and we do not see the same behavior.  Here are the results in may different time scales.

    Here are the results on the same board with a noisy fluorescent lamp on the same AC power-strip as the EVM.  The ballast used to charge/discharge the fluorescent bulb puts of a lot harsh energy on the AC supplies which interferes with other equipment powered on the same power strip.  Try powering off any noisy fluorescent lamps or other equipment that may be contaminating your power and try the measurements again.  Notice that with the lamp on we see a similar waveform as you're reporting.  As shown in the many images above the noise is not there with the lamp off.

  • Collin-san,
    Thank you very much for your cooperation.
    I will report this result, measurement environment and method to my customer.

    Thanks and regards,