Moteur de recherche de fiches techniques de composants électroniques
  French  ▼
ALLDATASHEET.FR

X  

AD7701AQ Fiches technique(PDF) 11 Page - Analog Devices

No de pièce AD7701AQ
Description  LC2MOS 16-Bit A/D Converter
Download  16 Pages
Scroll/Zoom Zoom In 100%  Zoom Out
Fabricant  AD [Analog Devices]
Site Internet  http://www.analog.com
Logo AD - Analog Devices

AD7701AQ Fiches technique(HTML) 11 Page - Analog Devices

Back Button AD7701AQ Datasheet HTML 7Page - Analog Devices AD7701AQ Datasheet HTML 8Page - Analog Devices AD7701AQ Datasheet HTML 9Page - Analog Devices AD7701AQ Datasheet HTML 10Page - Analog Devices AD7701AQ Datasheet HTML 11Page - Analog Devices AD7701AQ Datasheet HTML 12Page - Analog Devices AD7701AQ Datasheet HTML 13Page - Analog Devices AD7701AQ Datasheet HTML 14Page - Analog Devices AD7701AQ Datasheet HTML 15Page - Analog Devices Next Button
Zoom Inzoom in Zoom Outzoom out
 11 / 16 page
background image
–11–
REV. D
AD7701
VOLTAGE REFERENCE CONNECTIONS
The voltage applied to the VREF pin defines the analog input
range. The specified reference voltage is 2.5 V, but the AD7701
will operate with reference voltages from 1 V to 3 V with little
degradation in performance.
The reference input presents exactly the same dynamic load as
the analog input, but in the case of the reference input, source
resistance and long settling time introduce gain errors rather
than offset errors. Fortunately, most precision references have
sufficiently low output impedance and wide enough bandwidth
to settle to 10
µV within 62 clock cycles.
AGND
AD7701
+5V
AVDD
VREF
LT1019
Figure 14. Typical External Reference Connections
The digital filter of the AD7701 removes noise from the
reference input, just as it does with noise at the analog input,
and the same limitations apply regarding lack of noise rejection
at integer multiples of the sampling frequency. If reference noise
is a problem, some voltage references offer noise reduction
schemes using an external capacitor. Alternatively, a simple RC
filter may be used, as shown in Figure 15.
+5V
AD580
AGND
AD7701
AVDD
VREF
RF
13k
CF
100pF
Figure 15. Filtered Reference Input
The same considerations apply to this filter as to a filter at the
analog input. In this case:
[RF(CF +10 pF )]=
62
f CLKIN × ln
100 mV
×C
IN (CIN + CF )
V FSE
where:
fCLKIN is the master clock frequency
and
VFSE
is the maximum desired error in volts.
GROUNDING AND SUPPLY DECOUPLING
AGND is the ground reference voltage for the AD7701, and is
completely independent of DGND. Any noise riding on the
AGND input with respect to the system analog ground will
cause conversion errors. AGND should therefore be used as the
system ground and also as the ground for the analog input and
the reference voltage.
The analog and digital power supplies to the AD7701 are
independent and separately pinned out, to minimize coupling
between analog and digital sections of the device. The digital
filter will provide rejections of broadband noise on the power
supplies, except at integer multiples of the sampling frequency.
Therefore, the two analog supplies should be decoupled to
AGND using 100 nF ceramic capacitors to provide power
supply noise rejections at these frequencies. The two digital
supplies should similarly be decoupled to DGND.
ACCURACY AND AUTOCALIBRATION
Sigma-delta ADCs, like VFCs and other integrating ADCs, do
not contain any source of nonmonotonicity and inherently offer
no-missing-codes performance. The AD7701 achieves excellent
linearity (
±0.0007%) by the use of high quality, on-chip silicon
dioxide capacitors, which have a very low capacitance/voltage
coefficient.
The AD7701 offers two self-calibration modes using the on-chip
calibration microcontroller and SRAM. Table III is a truth table
for the calibration control inputs SC1 and SC2.
In the self-calibration mode, zero-scale is calibrated against the
AGND pin and full scale is calibrated against the VREF pin, to
remove internal errors.
Note that in the bipolar mode the AD7701 calibrates positive
full scale and midscale (bipolar zero).
In the system-calibration mode, the AD7701 calibrates its zero
and full scale to voltages present on the analog input pin in two
sequential steps. This allows system offsets and/or gain errors to
be nulled out.
SYSTEM
REF HI
AIN
SYSTEM
REF LO
ANALOG
MUX
A0
A1
SIGNAL
CONDITIONING
AD7701
MICRO
COMPUTER
SCLK
SDATA
CAL
SC1
SC2
Figure 16. Typical Connections for System Calibration
A typical system calibration scheme is shown in Figure 16. In
normal operation the analog signal is fed to the AD7701 via an
analog multiplexer. When the system is to be calibrated, AIN is
first switched to the system REF LO via the multiplexer and
CAL is strobed high, with SC1 and SC2 both high. AIN is then
switched to the system REF HI and CAL is strobed, with SC1
low and SC2 high. In this way, the effect of all error sources


Numéro de pièce similaire - AD7701AQ

FabricantNo de pièceFiches techniqueDescription
logo
Analog Devices
AD7701AQ AD-AD7701AQ Datasheet
319Kb / 21P
   LC2MOS 16-Bit A/D Converter
More results

Description similaire - AD7701AQ

FabricantNo de pièceFiches techniqueDescription
logo
Analog Devices
AD7701 AD-AD7701_17 Datasheet
319Kb / 21P
   LC2MOS 16-Bit A/D Converter
AD7703 AD-AD7703 Datasheet
251Kb / 16P
   LC2MOS 20-Bit A/D Converter
REV. D
AD7226BRSZ AD-AD7226BRSZ Datasheet
423Kb / 16P
   LC2MOS Quad 8-Bit D/A Converter
REV. D
AD7226 AD-AD7226_17 Datasheet
493Kb / 17P
   LC2MOS Quad 8-Bit D/A Converter
AD7226 AD-AD7226 Datasheet
247Kb / 12P
   LC2MOS Quad 8-Bit D/A Converter
REV. A
logo
Sanyo Semicon Device
LC7880M SANYO-LC7880M Datasheet
228Kb / 6P
   16 bit D/A CONVERTER
LC78866V SANYO-LC78866V Datasheet
138Kb / 6P
   16-bit A/D Converter?
LC78865M SANYO-LC78865M Datasheet
119Kb / 6P
   16-bit A/D Converter
logo
Analog Devices
AD7701 AD-AD7701_15 Datasheet
301Kb / 20P
   16-Bit A/D Converter
Rev. E
AD7111 AD-AD7111 Datasheet
175Kb / 8P
   LC2MOS LOGDAC Logarithmic D/A Converter
REV. 0
More results


Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16


Fiches technique Télécharger

Go To PDF Page


Lien URL




Politique de confidentialité
ALLDATASHEET.FR
ALLDATASHEET vous a-t-il été utile ?  [ DONATE ] 

À propos de Alldatasheet   |   Publicité   |   Contactez-nous   |   Politique de confidentialité   |   Echange de liens   |   Fabricants
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
Indian : Alldatasheet.in  |   Mexican : Alldatasheet.com.mx  |   British : Alldatasheet.co.uk  |   New Zealand : Alldatasheet.co.nz
Family Site : ic2ic.com  |   icmetro.com