This method of measurement of noise in an ADC is fairly simple and can
even be easily implemented on a system level after the ADC is placed in
the final system on a PCB. As stated above, we would need to ground the
analog input terminals of the ADC and take a number of readings to plot
the histogram. We will now see, with the help of the sample histogram in
Figure 3, how to calculate the noise parameters of an ADC.
Click on image to enlarge.
Figure 3: Grounded input histogram of an ADC
Figure 3 depicts
a typical grounded input histogram of an ADC. We can define a number of
parameters in terms of counts of ADC output with the help of this
histogram. For example, the peak-to-peak noise of an ADC is the span of x
axis over which the grounded input histogram exists. For example, the
peak-to-peak noise for the ADC corresponding to
Figure 3 is (1 –
(-3)) or 4 counts. Alternatively, it can be expressed in number of LSBs
of ADC output. In the aforementioned case, peak-to-peak noise would be
(log
2 4) = 2 LSBs.
In the next installment of this series (
ADC Guide Part 11), we will continue talking about the noise performance, EnoB, and SINAD specifications of an ADC.
Earlier articles are listed below:
About the authors
Sachin Gupta
is working as Product Marketing Engineer 2 with Cypress Semiconductor.
He holds a Bachelor’s degree in Electronics and Communications from Guru
Gobind Singh Indraprastha University, Delhi. He has several years of
experience in mixed signal application development. He can be reached at
sgup@cypress.com.
Akshay Phatak is an Applications Engineer
with Cypress Semiconductor. He holds a Bachelor's degree in Electronics
and Telecommunications form College of Engineering, Pune (India). He
likes to work on mixed-signal embedded systems. He can be reached
at akay@cypress.com.
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