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ADC中的ABC：理解ADC误差对系统性能的影响,The A,http://www.5idzw.com
SFDR is defined as the ratio of the RMS value of an input sine wave to the RMS value of the largest spur observed in the frequency domain using an FFT plot. It is typically expressed in dB. SFDR is important in certain communication applications that require maximizing the dynamic range of the ADC. Spurs prevent the ADC from converting small input signals, because the distortion component can be much larger than the signal of interest. This limits the dynamic range of the ADC. Note that a large spur in the frequency domain may not significantly affect the SNR, but will significantly affect the SFDR.
A quick check of the MAX1241 gain drift reveals a specification of 0.25ppm/°C or 12.5ppm over a 50°C temperature change, which is well within spec.
Now we have a viable solution that should prevent any hidden performance hiccups due to the specifications. Note for this example that we didn't address the AC performance at all. However, with your better understanding of the ADC specs and how they relate to the converter's performance, you will be armed with enough information to select the ADC that will give you the performance you need.，ADC中的ABC：理解ADC误差对系统性能的影响,The A
SFDR is defined as the ratio of the RMS value of an input sine wave to the RMS value of the largest spur observed in the frequency domain using an FFT plot. It is typically expressed in dB. SFDR is important in certain communication applications that require maximizing the dynamic range of the ADC. Spurs prevent the ADC from converting small input signals, because the distortion component can be much larger than the signal of interest. This limits the dynamic range of the ADC. Note that a large spur in the frequency domain may not significantly affect the SNR, but will significantly affect the SFDR.
Final Thoughts
Returning to the ADC example, assume we are measuring DC-type signals and our ADC accepts bipolar input signals. We choose the B grade of the MAX1241, which has 1LSB DNL error, 1LSB INL error (0.0244%), 3LSB offset error (3/4096 = 0.0732%), and gain of 4LSB (0.0977%). Adding the errors, we obtain a total error of 0.1953%. We can calibrate out the offset and gain errors, dropping our error to 0.0244%. As long as our voltage-reference error is less than 0.075% - 0.024% = 0.051%, we are within the error budget. A 5ppm/°C drift of more than 50 degrees equates to a 0.025% drift error, with a 0.026% error budget remaining. For 12-bit performance, we need to have a voltage reference with a voltage-noise specification considerably less than 1LSB (which is 2.5V/4096 = 610µV peak-to-peak or 102µV RMS). The MAX6166 is a good choice with 5ppm/°C drift and 30µV RMS wideband voltage noise. It also has ample source and sink current capability to drive the ADC (and additional circuitry if needed). Note that the 30µV noise spec equates to 180µV peak-to-peak, which is one-third of an LSB at the 12-bit level and one-sixth of an LSB at the 11-bit level (which is what our system requirement actually is).A quick check of the MAX1241 gain drift reveals a specification of 0.25ppm/°C or 12.5ppm over a 50°C temperature change, which is well within spec.
Now we have a viable solution that should prevent any hidden performance hiccups due to the specifications. Note for this example that we didn't address the AC performance at all. However, with your better understanding of the ADC specs and how they relate to the converter's performance, you will be armed with enough information to select the ADC that will give you the performance you need.，ADC中的ABC：理解ADC误差对系统性能的影响,The A
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