LM5171-Q1: Emissions and Spread-Spectrum

HI Brigitte - Thank you for the comments.

Do we have emissions reports for the LM5171-Q1?

Thanks,

Jacob

Hi Feng - Thank you for the information.

If we don't have any formal report, do we have any testing which may have been done on the LM5171 EVM?

Thanks,

Jacob

Hi Feng - Do we have test data for devices similar to the LM5171 which could be shared?

Or would it be possible to gather that information?

Especially since the device doesn't natively have dithering built in, but we have ways customers can add dithering by applying different signals to the device, it would be a useful reference for customers to see what the base performance of the device is and then what improvements can be made by our optional spread-spectrum measures.

Thanks,

Jacob

Hi Jacob,

We don't have any test data.

You may refer to EMI Reduction Technique, Dual Random Spread Spectrum.

Best Regards,

Feng

Thank you Feng.

For the dithering on the EVM. What is the amplitude of the 1kHz square wave being applied to the OSC pin via the SQIN pin?

In the case where the SQIN pin is grounded on the EVM, the effective Rosc resistance is 36.5kOhm which translates to an Fosc of 113.8kHz. If the other potential you apply to SQIN was 1V (the nominal Vosc voltage) then your set frequency is 108.4kHz. That alone give you a 5% change in switching frequency. Is that the intended signal application or would apply a different square wave voltage?

Thanks,

Jacob

Hi Jacob,

5% frequency change will be a good start point.

Typically, 2-3V 1kHz square waveform is required to get 5% dithering.

Best Regards,

Feng