Adc Evaluation; Hardware Selection; Tsw1200 Gui Introduction - Texas Instruments ADS5560EVM User Manual

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ADC Evaluation

This section describes how to set up a typical ADC evaluation system that is similar to what TI uses to
perform testing for data-sheet generation. Consequently, the information in this section is generic in nature
and is applicable to all high-speed, high-resolution ADC evaluations. This section covers signal tone
analysis, which yields ADC data-sheet figures of merit such as signal-to-noise ratio (SNR) and spurious
free dynamic range (SFDR).
4.1

Hardware Selection

To reveal the true performance of the ADC under evaluation, take great care in selecting both the ADC
signal source and the ADC clocking source.
4.1.1 Analog Input Signal Generator
When choosing the quality of the ADC analog input source, consider both harmonic distortion performance
of the signal generator and the noise performance of the source. In many cases, the harmonic distortion
performance of the signal generator is inferior to that of the ADC, and additional filtering is needed if users
expect to reproduce the ADC SFDR numbers found in the data sheet. Users can easily evaluate the
harmonic distortion of their signal generator by hooking it directly to a spectrum analyzer and measuring
the power of the output signal and comparing that to the power of the integer multiples of the output
signal's frequency. If the harmonic distortion is worse than the ADC under evaluation, the ADC digitizes
the performance of the signal generator and the true SFDR of the ADC is masked. To avoid this, TI
recommends that users provide additional LC filtering (BPF) after the signal generator output. Another
important metric when deciding on a signal generator is its noise performance. As with the distortion
performance, if the noise performance is worse than that of the ADC under evaluation, the ADC digitizes
SLAU260 – December 2008
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Figure 2. TSW1200 GUI Introduction
ADC Evaluation
ADS5560/62EVM 7