Datasheet AD7366-5, AD7367-5 (Analog Devices) - 14

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AD7366-5/AD7367-5 TERMINOLOGY Differential Nonlinearity (DNL) Total Harmonic Distortion (THD)
DNL is the difference between the measured and the ideal THD is the ratio of the rms sum of harmonics to the 1 LSB change between any two adjacent codes in the ADC. fundamental. For the AD7366-5/AD7367-5, it is defined as:
Integral Nonlinearity (INL)
2 2 2 2 2 V + V + V + V + V 2 3 4 5 6 THD(dB) = 20 log INL is the maximum deviation from a straight line passing V1 through the endpoints of the ADC transfer function. The where: endpoints of the transfer function are zero scale, a single (1) V LSB point below the first code transition and full scale, a point 1 is the rms amplitude of the fundamental. V 1 LSB above the last code transition. 2, V3, V4, V5, and V6 are the rms amplitudes of the second through the sixth harmonics.
Zero Code Error Peak Harmonic or Spurious Noise
This is the deviation of the midscale transition (all 1s to all 0s) Peak harmonic, or spurious noise, is defined as the ratio of the from the ideal VIN voltage, that is, AGND – ½ LSB for bipolar rms value of the next largest component in the ADC output ranges and 2 × VREF − 1 LSB for the unipolar range. spectrum (up to fS/2, excluding dc) to the rms value of the
Positive Full-Scale Error
fundamental. Normally, the value of this specification is deter- This is the deviation of the last code transition (011…110) to mined by the largest harmonic in the spectrum. However, for (011…111) from the ideal (that is, 4 × VREF − 1 LSB or 2 × VREF ADCs where the harmonics are buried in the noise floor, it is – 1 LSB) after the zero code error has been adjusted out. a noise peak.
Negative Full-Scale Error Channel-to-Channel Isolation
This is the deviation of the first code transition (10…000) to Channel-to-channel isolation is a measure of the level of cross- (10…001) from the ideal (that is, −4 × VREF + 1 LSB, −2 × VREF + talk between any two channels when operating in any of the 1 LSB, or AGND + 1 LSB) after the zero code error has been input ranges. It is measured by applying a full-scale, 150 kHz adjusted out. sine wave signal to all unselected input channels and determin- ing how much that signal is attenuated in the selected channel
Zero Code Error Match
with a 50 kHz signal. The figure given is the typical across all This is the difference in zero code error across all 12 channels. four channels for the AD7366-5/AD7367-5 (see the Figure 9 for
Positive Full-Scale Error Match
more information). This is the difference in positive full-scale error across all channels.
Intermodulation Distortion Negative Full-Scale Error Match
With inputs consisting of sine waves at two frequencies, fa This is the difference in negative full-scale error across all channels. and fb, any active device with nonlinearities creates distortion products at the sum, and different frequencies of mfa ± nfb
Track-and-Hold Acquisition Time
where m, n = 0, 1, 2, 3, and so on. Intermodulation distortion The track-and-hold amplifier returns to track mode at the end terms are those for which neither m nor n is equal to zero. of a conversion. Track-and-hold acquisition time is the time For example, the second-order terms include (fa + fb) and required for the output of the track-and-hold amplifier to reach (fa − fb), while the third-order terms include (2fa + fb), its final value, within ±½ LSB, after the end of conversion. (2fa − fb), (fa + 2fb), and (fa − 2fb).
Signal-to-Noise (+ Distortion) Ratio (SINAD)
The AD7366-5/AD7367-5 is tested using the CCIF standard This ratio is the measured ratio of signal-to-noise (+ distortion) where two input frequencies near the top end of the input at the output of the ADC. The signal is the rms amplitude of the bandwidth are used. In this case, the second-order terms are fundamental. Noise is the sum of all nonfundamental signals up usually distanced in frequency from the original sine waves, to half the sampling frequency (f while the third-order terms are usually at a frequency close to S/2), excluding dc. The ratio is dependent on the number of quantization levels in the digitiza- the input frequencies. As a result, the second- and third-order tion process: the more levels, the smaller the quantization noise. terms are specified separately. The calculation of the intermodula- The theoretical signal-to-noise (+ distortion) ratio for an ideal tion distortion is as per the THD specification, where it is the ratio N-bit converter with a sine wave input is given by: of the rms sum of the individual distortion products to the rms amplitude of the sum of the fundamentals expressed in decibels. Signal-to-Noise (+ Distortion) = (6.02N + 1.76) dB Thus, for a 12-bit converter, this is 74 dB. Rev. B | Page 14 of 28 Document Outline FEATURES FUNCTIONAL BLOCK DIAGRAM GENERAL DESCRIPTION PRODUCT HIGHLIGHTS TABLE OF CONTENTS REVISION HISTORY SPECIFICATIONS AD7366-5 SPECIFICATIONS AD7367-5 SPECIFICATIONS TIMING SPECIFICATIONS ABSOLUTE MAXIMUM RATINGS ESD CAUTION PIN CONFIGURATION AND FUNCTION DESCRIPTIONS TYPICAL PERFORMANCE CHARACTERISTICS TERMINOLOGY THEORY OF OPERATION CIRCUIT INFORMATION CONVERTER OPERATION ANALOG INPUTS TRANSFER FUNCTION Track-and-Hold TYPICAL CONNECTION DIAGRAM DRIVER AMPLIFIER CHOICE VDRIVE REFERENCE MODES OF OPERATION NORMAL MODE SHUTDOWN MODE POWER-UP TIMES SERIAL INTERFACE MICROPROCESSOR INTERFACING AD7366-5/AD7367-5 TO ADSP-218x AD7366-5/AD7367-5 TO ADSP-BF53x AD7366-5/AD7367-5 TO TMS320VC5506 AD7366-5/AD7367-5 TO DSP563xx APPLICATION HINTS LAYOUT AND GROUNDING EVALUATING THE AD7366-5/AD7367-5 OUTLINE DIMENSIONS ORDERING GUIDE