gain and offset error in adc Thatcher Idaho

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gain and offset error in adc Thatcher, Idaho

These are analog errors caused by many factors in the DAC and in the external signal path. With a specification of 0.5LSB, the accuracy is 0.012%, and this accounts for only about 16% (0.012%/0.075%) of our ADC error budget limit. However for simplicity we will assume VREF). Oversampling improves the ADC's dynamic performance by effectively reducing its noise floor.

The full-scale gain error of any data converter can be affected by the choice of reference used to measure the gain error. Figure 5. Your cache administrator is webmaster. Sometimes, much to the surprise and consternation of engineers, a data-acquisition system will exhibit much lower performance than expected.

Figure 6. As long as our voltage-reference error is less than 0.075% - 0.024% = 0.051%, we are within the error budget. SNR is similar to SINAD, except that it does not include the harmonic content. For a sinewave, the RMS value is 2/2 (or 0.707) times the peak value, which is 0.354 times the peak-to-peak value.

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%). This, however, is a cumbersome process, as each ADC must be compensated individually and the compensation process is a time-consuming effort. The signals f1 and f2 are of equal amplitude and very close to one another in frequency. In many DAC systems an external voltage reference is used to set the gain.

Load Regulation The final spec is reference load regulation. Nonlinear errors include integral non-linearity error and differential non-linearity error. In the figure, feedthrough on the DAC output is the result of noise from the serial clock signal. Now we have a viable solution that should prevent any hidden performance hiccups due to the specifications.

Gain error for an ADC and a DAC. A thorough understanding of ADC specifications will reveal subtleties that often lead to less-than-desired performance. Your cache administrator is webmaster. COMMUNITY Latest Blogs Design Ideas Events Loading...

These often occur in industrial control, environmental monitoring, battery testing, and power consumption. Causes of Errors Given the multiple types of DAC errors, it is virtually a "given" that the DAC's output will only be used if the signal is run through some kind The content on this webpage is protected by copyright laws of the United States and of foreign countries. As with offset error, you lose dynamic range with gain error.

SFDR is specified in decibels relative to the carrier (dBc). The first specification to review is SINAD or SNR. contact us. © 2015 Maxim Integrated | Contact Us | Careers | Legal | Privacy | Cookie Policy | Site Map | Follow Us: © 2015 Maxim Integrated | Contact Us Sign up now!

Generated Mon, 17 Oct 2016 03:04:09 GMT by s_wx1127 (squid/3.5.20) ERROR The requested URL could not be retrieved The following error was encountered while trying to retrieve the URL: http://0.0.0.9/ Connection Prototyping frequently does not reveal the significance of this error, because parts are often from a similar lot and thus the test results do not take into account the extremes that Figure 5. For a DAC with more than one input channel, crosstalk is the amount of noise that appears on a DAC output when another DAC output channel is updated.

Offset and gain errors. As frequency increases toward the Nyquist limit, SINAD decreases. This application note describes these DAC errors and their sources, and then describes methods for calibrating out that error in both the analog and digital domains. There is a good reason why manufacturers do not give maximum limits: This increases the cost.

In bipolar systems, offset error shifts the transfer function but does not reduce the number of available codes (Figure 2). All ADCs introduce static errors to measurements. SINAD is defined as the RMS value of an input sine wave to the RMS value of the noise of the converter (from DC to the Nyquist frequency, including harmonic [total A similar version of this article appeared in the March 23, 2012 issue of Planet Analog magazine.

Forgot Your Password? For example, if a full-scale input voltage is applied and the code obtained is 4050 instead of the ideal 4096 (for a 12-bit converter), this is defined as negative gain error, If the initial offset is calibrated and the temperature moves, there will be an error introduced due to the drift term that can negate the effects of the calibration. Other Temperature Effects Continuing with the topic of temperature, two specifications that are often given little attention are offset drift and gain drift.

Thus, the SNR should always be better than the SINAD. For example, assume a reading is done at temperature X. The line is perfectly linear. Figure 3b.Figures 3a and 3b.

Gain Error Measurement in this 3-bit ADC causes the output code to reach maximum too early. SSBW is often limited by the performance of the associated track-and-hold amplifier. Adding the errors, we obtain a total error of 0.1953%. DNL error: no missing codes.

In one, you shift the x and y axes of the transfer function so that the negative full-scale point aligns with the zero point of a unipolar system (Figure 3a). Gain Matching Gain matching indicates how well the gains of all channels in a multichannel ADC are matched to each other. The binary code (zero scale to full scale) ranges from all zeros (00...000) to the positive full-scale value of all ones (11...111). The system returned: (22) Invalid argument The remote host or network may be down.

Similarly, a sequence decreases monotonically if for every n, Pn + 1 is less than or equal to Pn. However, the error measured at zero-scale is at the midpoint of the bipolar transfer functions. (See Offset Error (Unipolar).) Offset Error (Unipolar) Offset error, often called 'zero-scale' error, indicates how well For requests to copy this content, contact us. In Figures 1b, 1c, and 1d, three DNL error values are shown.

For some systems, the reference accuracy is not a big issue, as the temperature is held constant, eliminating the drift problem. All of the characteristics shown in Figure 2 above are perfectly linear; they are never exactly linear as shown in Figure 3 below. Download Download, PDF Format(189.9kB) © Oct 27, 2009, Maxim Integrated Products, Inc. Gain error is easily corrected in software with a linear function y = (m1/m2)(x), where m1 is the slope of the ideal transfer function and m2 is the slope of the

This method is most accurate when the all error terms are uncorrelated (which may or may not be the case). FS Gain Error (DACs) The full-scale gain error of an digital-to-analog converter (DAC) is the difference between the actual and the ideal output span.