数据搜索系统,热门电子元器件搜索 |
|
AD783AR 数据表(PDF) 7 Page - Analog Devices |
|
AD783AR 数据表(HTML) 7 Page - Analog Devices |
7 / 8 page AD783 REV. A –7– The AD783 does not provide separate analog and digital ground leads as is the case with most A-to-D converters. The common pin is the single ground terminal for the device. It is the refer- ence point for the sampled input voltage and the held output voltage and also the digital ground return path. The common pin should be connected to the reference (analog) ground of the A-to-D converter with a separate ground lead. Since the analog and digital grounds in the AD783 are connected internally, the common pin should also be connected to the digital ground, which is usually tied to analog common at the A-to-D converter. Figure 3 illustrates the recommended decoupling and grounding practice. NOISE CHARACTERISTICS Designers of data conversion circuits must also consider the effect of noise sources on the accuracy of the data acquisition system. A sample-and-hold amplifier that precedes the A-to-D converter introduces some noise and represents another source of uncertainty in the conversion process. The noise from the AD783 is specified as the total output noise, which includes both the sampled wideband noise of the SHA in addition to the band limited output noise. The total output noise is the rms sum of the sampled dc uncertainty and the hold mode noise. A plot of the total output noise vs. the equivalent input bandwidth of the converter being used is given in Figure 4. 300 0 1k 10M 200 100 10k 1M 100k FREQUENCY – Hz Figure 4. RMS Noise vs. Input Bandwidth of ADC DRIVING THE ANALOG INPUTS For best performance, it is important to drive the AD783 analog input from a low impedance signal source. This enhances the sampling accuracy by minimizing the analog and digital cross- talk. Signals which come from higher impedance sources (e.g., over 5 k Ω) will have a relatively higher level of crosstalk. For applications where signals have high source impedance, an operational amplifier buffer in front of the AD783 is required. The AD711 (precision BiFET op amp) is recommended for these applications. HIGH FREQUENCY SAMPLING Aperture jitter and distortion are the primary factors which limit frequency domain performance of a sample-and-hold amplifier. Aperture jitter modulates the phase of the hold command and produces an effective noise on the sampled analog input. The magnitude of the jitter induced noise is directly related to the frequency of the input signal. A graph showing the magnitude of the jitter induced error vs. frequency of the input signal is given in Figure 5. The accuracy in sampling high frequency signals is also constrained by the distortion and noise created by the sample-and-hold. The level of distortion increases with frequency and reduces the “effective number of bits” of the conversion. Measurements of Figures 6 and 7 were made using a 14-bit A/D converter with VIN = 5 V p-p and a sample frequency of 100 kSPS. 1% 1k 1M 0.1% 0.01% 10k 100k FREQUENCY – Hz APERTURE JITTER TYPICAL AT 20ps 1/2 BIT @ 8 BITS 1/2 BIT @ 10 BITS 1/2 BIT @ 12 BITS 1/2 BIT @ 14 BITS Figure 5. Error Magnitude vs. Frequency –65 –95 1M –80 –90 1k –85 100 –70 –75 100k 10k FREQUENCY – Hz Figure 6. Total Harmonic Distortion vs. Frequency 90 0 1M 20 10 10k 1k 30 40 50 60 70 80 100k FREQUENCY – Hz Figure 7. Signal/(Noise and Distortion) vs. Frequency |
类似零件编号 - AD783AR |
|
类似说明 - AD783AR |
|
|
链接网址 |
隐私政策 |
ALLDATASHEETCN.COM |
ALLDATASHEET是否为您带来帮助? [ DONATE ] |
关于 Alldatasheet | 广告服务 | 联系我们 | 隐私政策 | 链接交换 | 制造商名单 All Rights Reserved©Alldatasheet.com |
Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
Family Site : ic2ic.com |
icmetro.com |