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Low frequency output voltage noise in ADCLK905 / ADCLK907 / ADCLK925 family

Question asked by Tim.Timer on Aug 3, 2015
Latest reply on Oct 2, 2015 by JLKeip

Hello,

 

i wonder if the RMS voltage noise of the ADCLK905 family of chips can be calculated from the specifications. More specifically: If i apply a constant input signal, what is the output voltage RMS noise in the frequency range of 0-100MHz (assuming a prefect low pass)?

 

I hope this can be calculated from the specification of: -161 dbc/Hz phase noise, but i am not very familiar with this quantity. Is the following calculation sensible?

-161 dbc/Hz * 100MHz = 10e-16 * 10e8 = 10e-8  in units of signal to noise power.

Voltage noise is then sqrt(10e-8) = 10e-4

The output signal voltage is 800mV, so the RMS noise 800mV * 10e-4 = 0.4 µV

0.4 µV rms noise seems very low for a chip that is optimized for fast transitions, so i assume i made an error..

 

I hope this made sense. Any help is greatly appreciated.

 

Sincerely,

Tim

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