Electronic Components Datasheet Search
  English  ▼

Delete All
ON OFF
ALLDATASHEET.COM

X  

Preview PDF Download HTML

AD7329 Datasheet(PDF) 23 Page - Analog Devices

Part No. AD7329
Description  1 MSPS, 8-Channel, Software-Selectable, True Bipolar Input, 12-Bit Plus Sign ADC
Download  40 Pages
Scroll/Zoom Zoom In 100% Zoom Out
Maker  AD [Analog Devices]
Homepage  http://www.analog.com
Logo 

AD7329 Datasheet(HTML) 23 Page - Analog Devices

Zoom Inzoom in Zoom Outzoom out
 23 / 40 page
background image
AD7329
Rev. 0 | Page 23 of 40
DRIVER AMPLIFIER CHOICE
In applications where the harmonic distortion and signal-to-
noise ratio are critical specifications, the analog input of the
AD7329 should be driven from a low impedance source. Large
source impedances significantly affect the ac performance of the
ADC and can necessitate the use of an input buffer amplifier.
When no amplifier is used to drive the analog input, the source
impedance should be limited to low values. The maximum
source impedance depends on the amount of THD that can be
tolerated in the application. The THD increases as the source
impedance increases and performance degrades. Figure 21 and
Figure 22 show graphs of the THD vs. the analog input
frequency for various source impedances. Depending on the
input range and analog input configuration selected, the
AD7329 can handle source impedances of up to 4 kΩ before the
THD starts to degrade.
Due to the programmable nature of the analog inputs on the
AD7329, the choice of op amp used to drive the inputs is a
function of the particular application and depends on the input
configuration and the analog input voltage ranges selected.
The driver amplifier must be able to settle for a full-scale step to
a 13-bit level, 0.0122%, in less than the specified acquisition
time of the AD7329. An op amp such as the AD8021 meets this
requirement when operating in single-ended mode. The AD8021
needs an external compensating NPO type of capacitor. The
AD8022 can also be used in high frequency applications where
a dual version is required. For lower frequency applications, op
amps such as the AD797, AD845, and AD8610 can be used with
the AD7329 in single-ended mode configuration.
Table 8. Typical AC Performance
Using Different Op Amps in Single-Ended Mode
No
Buffer
AD845
AD8021
AD8610
±10 V
SNR (dB)
74.24
74.03
73.78
73.88
SNRD (dB)
72.42
74.88
72.11
71.98
THD (dB)
−77.05
−75.95
−77.04
−76.47
Table 9. Typical AC Performance
Using Different Op Amps in Differential Mode
No
Buffer
AD845
AD8021
AD8610
±10 V
SNR (dB)
77.16
76.81
76.95
76.76
SNRD (dB)
76.50
76.02
76.78
75.89
THD (dB)
−84.91
−83.74
−90.55
−83.24
Differential operation requires that VIN+ and VIN− be
simultaneously driven with two signals of equal amplitude that
are 180° out of phase. The common mode must be set up
externally to the AD7329. The common-mode range is
determined by the REFIN/REFOUT voltage, the VCC supply voltage,
and the particular amplifier used to drive the analog inputs.
Differential mode with either an ac input or a dc input provides
the best THD performance over a wide frequency range. Because
not all applications have a signal preconditioned for differential
operation, there is often a need to perform a single-ended-to-
differential conversion.
This single-ended-to-differential conversion can be performed
using an op amp pair. Typical connection diagrams for an op
amp pair are shown in Figure 45 and Figure 46. In Figure 45,
the common-mode signal is applied to the noninverting input
of the second amplifier.


Html Pages

1  2  3  4  5  6  7  8  9  10  11  12  13  14  15  16  17  18  19  20  21  22  23  24  25  26  27  28  29  30  31  32  33  34  35  36  37  38  39  40 


Datasheet Download




Link URL




Privacy Policy
ALLDATASHEET.COM
Does ALLDATASHEET help your business so far?  [ DONATE ]  

About Alldatasheet   |   Advertisement   |   Datasheet Upload   |   Contact us   |   Privacy Policy   |   Alldatasheet API   |   Link Exchange   |   Manufacturer List
All Rights Reserved© Alldatasheet.com


Mirror Sites
English : Alldatasheet.com  |   English : Alldatasheet.net  |   Chinese : Alldatasheetcn.com  |   German : Alldatasheetde.com  |   Japanese : Alldatasheet.jp
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