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AD7357YRUZ Datasheet(PDF) 10 Page  Analog Devices 

AD7357YRUZ Datasheet(HTML) 10 Page  Analog Devices 
10 / 20 page AD7357 Rev. 0  Page 10 of 20 TERMINOLOGY Integral Nonlinearity (INL) INL is the maximum deviation from a straight line passing through the endpoints of the ADC transfer function. The endpoints of the transfer function are zero scale (1 LSB below the first code transition) and full scale (1 LSB above the last code transition). Differential Nonlinearity (DNL) DNL is the difference between the measured and the ideal 1 LSB change between any two adjacent codes in the ADC. Negative FullScale Error Negative fullscale error is the deviation of the first code transi tion (00 … 000) to (00 … 001) from the ideal (that is, −VREF + 0.5 LSB) after the midscale error has been adjusted out. Negative FullScale Error Match Negative fullscale error match is the difference in negative full scale error between the two ADCs. Midscale Error Midscale error is the deviation of the midscale code transition (011 … 111) to (100 … 000) from the ideal (that is, 0 V). Midscale Error Match Midscale error match is the difference in midscale error between the two ADCs. Positive FullScale Error Positive fullscale error is the deviation of the last code transi tion (111 … 110) to (111 … 111) from the ideal (that is, VREF − 1.5 LSB) after the midscale error has been adjusted out. Positive FullScale Error Match Positive fullscale error match is the difference in positive full scale error between the two ADCs. ADCtoADC Isolation ADCtoADC isolation is a measure of the level of crosstalk between ADC A and ADC B. It is measured by applying a full scale 1 MHz sine wave signal to one of the two ADCs and applying a fullscale signal of variable frequency to the other ADC. The ADCtoADC isolation is defined as the ratio of the power of the 1 MHz signal on the converted ADC to the power of the noise signal on the other ADC that appears in the FFT. The noise frequency on the unselected channel varies from 100 kHz to 2.5 MHz. Power Supply Rejection Ratio (PSRR) PSRR is defined as the ratio of the power in the ADC output at fullscale frequency, f, to the power of a 100 mV pp sine wave applied to the ADC VDD supply of the frequency, fS. The frequency of the input varies from 5 kHz to 25 MHz. PSRR (dB) = 10 log(Pf/PfS) where: Pf is the power at frequency, f, in the ADC output. PfS is the power at frequency, fS, in the ADC output. CommonMode Rejection Ratio (CMRR) CMRR is defined as the ratio of the power in the ADC output at fullscale frequency, f, to the power of a 100 mV pp sine wave applied to the commonmode voltage of VIN+ and VIN− of frequency, fS, as follows: CMRR (dB) = 10log (Pf/PfS) where: Pf is the power at frequency, f, in the ADC output. PfS is the power at frequency, fS, in the ADC output. TrackandHold Acquisition Time The trackandhold amplifier returns to track mode at the end of a conversion. The trackandhold acquisition time is the time required for the output of the trackandhold amplifier to reach its final value, within ±1 LSB, after the end of conversion. Signalto(Noise + Distortion) Ratio (SINAD) SINAD is the measured ratio of signalto(noise + distortion) at the output of the ADC. The signal is the rms amplitude of the fundamental. Noise is the sum of all nonfundamental signals up to half the sampling frequency (fS/2), excluding dc. The ratio is dependent on the number of quantization levels in the digitiza tion process; the more levels, the smaller the quantization noise. The theoretical SINAD for an ideal Nbit converter with a sine wave input is given by SINAD = (6.02 N + 1.76) dB Thus, for a 12bit converter, SINAD is 74 dB and for a 14bit converter, SINAD is 86 dB. Total Harmonic Distortion (THD) THD is the ratio of the rms sum of harmonics to the funda mental. For the AD7357, it is defined as () 1 6 5 4 3 2 V V V V V V THD 2 2 2 2 2 log 20 dB + + + + − = where: V1 is the rms amplitude of the fundamental. V2, V3, V4, V5, and V6 are the rms amplitudes of the second through the sixth harmonics. Peak Harmonic or Spurious Noise Peak harmonic or spurious noise is defined as the ratio of the rms value of the next largest component in the ADC output spectrum (up to fS/2 and excluding dc) to the rms value of the fundamental. Normally, the value of this specification is determined by the largest harmonic in the spectrum, but for ADCs where the harmonics are buried in the noise floor, it is a noise peak. 
