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

X  

AD7874SQ3 Fiches technique(PDF) 6 Page - Analog Devices

No de pièce AD7874SQ3
Description  LC2MOS 4-Channel, 12-Bit Simultaneous Sampling Data Acquisition System
Download  16 Pages
Scroll/Zoom Zoom In 100%  Zoom Out
Fabricant  AD [Analog Devices]
Site Internet  http://www.analog.com
Logo AD - Analog Devices

AD7874SQ3 Fiches technique(HTML) 6 Page - Analog Devices

Back Button AD7874SQ3 Datasheet HTML 2Page - Analog Devices AD7874SQ3 Datasheet HTML 3Page - Analog Devices AD7874SQ3 Datasheet HTML 4Page - Analog Devices AD7874SQ3 Datasheet HTML 5Page - Analog Devices AD7874SQ3 Datasheet HTML 6Page - Analog Devices AD7874SQ3 Datasheet HTML 7Page - Analog Devices AD7874SQ3 Datasheet HTML 8Page - Analog Devices AD7874SQ3 Datasheet HTML 9Page - Analog Devices AD7874SQ3 Datasheet HTML 10Page - Analog Devices Next Button
Zoom Inzoom in Zoom Outzoom out
 6 / 16 page
background image
AD7874
REV. C
–6–
CONVERTER DETAILS
The AD7874 is a complete 12-bit, 4-channel data acquisition
system. It is comprised of a 12-bit successive approximation
ADC, four high speed track/hold circuits, a four-channel analog
multiplexer and a 3 V Zener reference. The ADC uses a succes-
sive approximation technique and is based on a fast-settling,
voltage switching DAC, a high speed comparator, a fast CMOS
SAR and high speed logic.
Conversion is initiated on the rising edge of CONVST. All four
input track/holds go from track to hold on this edge. Conversion
is first performed on the Channel 1 input voltage, then Channel
2 is converted and so on. The four results are stored in on-chip
registers. When all four conversions have been completed, INT
goes low indicating that data can be read from these locations.
The conversion sequence takes either 78 or 79 rising clock edges
depending on the synchronization of CONVST with CLK. In-
ternal delays and reset times bring the total conversion time
from CONVST going high to INT going low to 32.5
µs maxi-
mum for a 2.5 MHz external clock. The AD7874 uses an im-
plicit addressing scheme whereby four successive reads to the
same memory location access the four data words sequentially.
The first read accesses Channel 1 data, the second read accesses
Channel 2 data and so on. Individual data registers cannot be
accessed independently.
INTERNAL REFERENCE
The AD7874 has an on-chip temperature compensated buried
Zener reference which is factory trimmed to 3 V
± 10 mV (see
Figure 3). The reference voltage is provided at the REF OUT
pin. This reference can be used to provide both the reference
voltage for the ADC and the bipolar bias circuitry. This is
achieved by connecting REF OUT to REF IN.
TEMPERATURE
COMPENSATION
AD7874
V
DD
V
SS
REF OUT
Figure 3. AD7874 Internal Reference
The reference can also be used as a reference for other compo-
nents and is capable of providing up to 500
µA to an external
load. In systems using several AD7874s, using the REF OUT of
one device to provide the REF IN for the other devices ensures
good full-scale tracking between all the AD7874s. Because the
AD7874 REF IN is buffered, each AD7874 presents a high im-
pedance to the reference so one AD7874 REF OUT can drive
several AD7874 REF INs.
The maximum recommended capacitance on REF OUT for
normal operation is 50 pF. If the reference is required for other
system uses, it should be decoupled to AGND with a 200
Ω re-
sistor in series with a parallel combination of a 10
µF tantalum
capacitor and a 0.1
µF ceramic capacitor.
EXTERNAL REFERENCE
In some applications, the user may require a system reference or
some other external reference to drive the AD7874 reference in-
put. Figure 4 shows how the AD586 5 V reference can be used
to provide the 3 V reference required by the AD7874 REF IN.
GND
+V
IN
V
OUT
AGND
10k
15k
1k
V
IN1
TO INTERNAL
COMPARATOR
TRACK/HOLD 1
TO ADC
REFERENCE
CIRCUITRY
7R*
2.1R*
3R*
AD7874**
REF
IN
15V
+
AD586
*R = 3.6k
Ω TYP
**ADDITIONAL PINS OMITTED FOR CLARITY
Figure 4. AD586 Driving AD7874 REF IN
TRACK-AND-HOLD AMPLIFIER
The track-and-hold amplifier on each analog input of the
AD7874 allows the ADC to accurately convert an input sine
wave of 20 V p-p amplitude to 12-bit accuracy. The input band-
width of the track/hold amplifier is greater than the Nyquist rate
of the ADC even when the ADC is operated at its maximum
throughput rate. The small signal 3 dB cutoff frequency occurs
typically at 500 kHz.
The four track/hold amplifiers sample their respective input
channels simultaneously. The aperture delay of the track/hold
circuits is small and, more importantly, is well matched across
the four track/holds on one device and also well matched from
device to device. This allows the relative phase information be-
tween different input channels to be accurately preserved. It also
allows multiple AD7874s to sample more than four channels
simultaneously.
The operation of the track/hold amplifiers is essentially transpar-
ent to the user. Once conversion is initiated, the four channels
are automatically converted and there is no need to select which
channel is to be digitized.
ANALOG INPUT
The analog input of Channel 1 of the AD7874 is as shown in
Figure 4. The analog input range is
±10 V into an input resis-
tance of typically 30 k
Ω. The designed code transitions occur
midway between successive integer LSB values (i.e., 1/2 LSB,
3/2 LSBs, 5/2 LSBs, . . . FS – 3/2 LSBs). The output code is
2s complement binary with 1 LSB = FS/4096 = 20 V/4096 =
4.88 mV. The ideal input/output transfer function is shown in
Figure 5.


Numéro de pièce similaire - AD7874SQ3

FabricantNo de pièceFiches techniqueDescription
logo
Analog Devices
AD7874SQ3 AD-AD7874SQ3 Datasheet
326Kb / 16P
   LC2MOS 4-Channel, 12-Bit Simultaneous Sampling Data Acquisition System
REV. C
AD7874SQ3 AD-AD7874SQ3 Datasheet
326Kb / 16P
   LC2MOS 4-Channel, 12-Bit Simultaneous Sampling Data Acquisition System
REV. C
More results

Description similaire - AD7874SQ3

FabricantNo de pièceFiches techniqueDescription
logo
Analog Devices
AD7874SQ AD-AD7874SQ Datasheet
326Kb / 16P
   LC2MOS 4-Channel, 12-Bit Simultaneous Sampling Data Acquisition System
REV. C
AD7874BNZ AD-AD7874BNZ Datasheet
326Kb / 16P
   LC2MOS 4-Channel, 12-Bit Simultaneous Sampling Data Acquisition System
REV. C
AD7874 AD-AD7874 Datasheet
414Kb / 16P
   LC2MOS 4-Channel, 12-Bit Simultaneous Sampling Data Acquisition System
REV. C
AD7874 AD-AD7874_17 Datasheet
448Kb / 17P
   4-Channel, 12-Bit Simultaneous Sampling Data Acquisition System
AD7874 AD-AD7874_15 Datasheet
418Kb / 16P
   LC MOS 4-Channel, 12-Bit Simultaneous Sampling Data Acquisition System
REV. C
ADAS3023 AD-ADAS3023 Datasheet
617Kb / 32P
   16-Bit, 8-Channel Simultaneous Sampling Data Acquisition System
REV. 0
AD7890 AD-AD7890 Datasheet
302Kb / 20P
   LC2MOS 8-Channel, 12-Bit Serial, Data Acquisition System
REV. A
AD7891 AD-AD7891 Datasheet
173Kb / 20P
   LC2MOS 8-Channel, 12-Bit High Speed Data Acquisition System
REV. A
AD7891YSZ-2 AD-AD7891YSZ-2 Datasheet
1Mb / 20P
   LC2MOS 8-Channel, 12-Bit High Speed Data Acquisition System
REV. D
AD7891AP AD-AD7891AP Datasheet
316Kb / 20P
   LC2MOS 8-Channel, 12-Bit High Speed Data Acquisition System
REV. D
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