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AD7927 データシート(PDF) 7 Page - Analog Devices |
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AD7927 データシート(HTML) 7 Page - Analog Devices |
7 / 20 page REV. 0 AD7927 –7– TERMINOLOGY Integral Nonlinearity This is the maximum deviation from a straight line passing through the endpoints of the ADC transfer function. The end- points of the transfer function are zero-scale, a point 1 LSB below the first code transition, and full-scale, a point 1 LSB above the last code transition. Differential Nonlinearity This is the difference between the measured and the ideal 1 LSB change between any two adjacent codes in the ADC. Offset Error This is the deviation of the first code transition (00 . . . 000) to (00 . . . 001) from the ideal, i.e., AGND + 1 LSB. Offset Error Match This is the difference in offset error between any two channels. Gain Error This is the deviation of the last code transition (111 . . . 110) to (111 . . . 111) from the ideal (i.e., REFIN – 1 LSB) after the offset error has been adjusted out. Gain Error Match This is the difference in gain error between any two channels. Zero Code Error This applies when using the twos complement output coding option, in particular to the 2 ¥ REFIN input range with –REFIN to +REFIN biased about the REFIN point. It is the deviation of the midscale transition (all 0s to all 1s) from the ideal VIN volt- age, i.e., REFIN – 1 LSB. Zero Code Error Match This is the difference in Zero Code Error between any two channels. Positive Gain Error This applies when using the twos complement output coding option, in particular to the 2 ¥ REFIN input range with –REFIN to +REFIN biased about the REFIN point. It is the deviation of the last code transition (011. . .110) to (011 . . . 111) from the ideal (i.e., +REFIN – 1 LSB) after the Zero Code Error has been adjusted out. Positive Gain Error Match This is the difference in Positive Gain Error between any two channels. Negative Gain Error This applies when using the twos complement output coding option, in particular to the 2 ¥ REFIN input range with –REF IN to +REFIN biased about the REFIN point. It is the deviation of the first code transition (100 . . . 000) to (100 . . . 001) from the ideal (i.e., –REF IN + 1 LSB) after the Zero Code Error has been adjusted out. Negative Gain Error Match This is the difference in Negative Gain Error between any two channels. Channel-to-Channel Isolation Channel-to-Channel Isolation is a measure of the level of crosstalk between channels. It is measured by applying a full-scale 400 kHz sine wave signal to all seven nonselected input channels and deter- mining how much that signal is attenuated in the selected channel with a 50 kHz signal. The figure is given worst case across all eight channels for the AD7927. PSR (Power Supply Rejection) Variations in power supply will affect the full-scale transition, but not the converter’s linearity. Power supply rejection is the maximum change in full-scale transition point due to a change in power supply voltage from the nominal value. See Typical Performance Characteristics. Track-and-Hold Acquisition Time The track-and-hold amplifier returns into track mode at the end of conversion. Track-and-hold acquisition time is the time required for the output of the track-and-hold amplifier to reach its final value, within ±1 LSB, after the end of conversion. Signal-to-(Noise + Distortion) Ratio This is the measured ratio of signal-to-(noise + distortion) at the output of the A/D converter. 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 digiti- zation process; the more levels, the smaller the quantization noise. The theoretical signal-to-(noise + distortion) ratio for an ideal N-bit converter with a sine wave input is given by: Signal to Noise Distortion N dB -- () ( . . ) += + 602 176 Thus for a 12-bit converter, this is 74 dB. Total Harmonic Distortion Total harmonic distortion (THD) is the ratio of the rms sum of harmonics to the fundamental. For the AD7927, it is defined as: THD dB VVVVV V () log = ++++ 20 2 2 3 2 4 2 5 2 6 2 1 where V1 is the rms amplitude of the fundamental and V2, V3, V4, V5, and V6 are the rms amplitudes of the second through the sixth harmonics. |
同様の部品番号 - AD7927 |
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同様の説明 - AD7927 |
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