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PDF ( 数据手册 , 数据表 ) AD674B

零件编号 AD674B
描述 Complete 12-Bit A/D Converters
制造商 Analog Devices
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AD674B 数据手册, 描述, 功能
a
FEATURES
Complete Monolithic 12-Bit A/D Converters with
Reference, Clock, and Three-State Output Buffers
Industry Standard Pinout
High Speed Upgrades for AD574A
8- and 16-Bit Microprocessor Interface
8 s (Max) Conversion Time (AD774B)
15 s (Max) Conversion Time (AD674B)
؎5 V, ؎10 V, 0 V–10 V, 0 V–20 V Input Ranges
Commercial, Industrial, and Military Temperature
Range Grades
MIL-STD-883-Compliant Versions Available
Complete 12-Bit
A/D Converters
AD674B /AD774B
FUNCTIONAL BLOCK DIAGRAM
5V SUPPLY
VLOGIC
DATA MODE SELECT
12/8
CHIP SELECT
CS
BYTE ADDRESS/
SHORT CYCLE A0
READ/CONVERT R/C
1
2
3
4
5
CHIP ENABLE
CE 6
12V/15V SUPPLY
VCC
10V REFERENCE
REF OUT
7
8
ANALOG COMMON
AC
9
REFERENCE INPUT
REF IN
10
–12V/–15V SUPPLY
VEE 11
BIPOLAR OFFSET
BIPOFF
12
10V SPAN INPUT
10VIN 13
20V SPAN INPUT
20VIN
14
CONTROL
CLOCK
SAR 12
10V
REF
COMP
+
I DAC
MSB
N
Y
3
B
B
S
T
L
E
A
T
A
EN
Y
OB
UB
TL
PE
U
TB
199.95
k
I REF
+
DAC
N
VEE
BN
UY
FB
FB
EL
RE
S
C
LSB
VOLTAGE
DIVIDER AD674B/AD774B
28
STATUS
STS
27 DB11 (MSB)
26 DB10
25 DB9
24 DB8
23 DB7
22 DB6
21 DB5
20 DB4
19 DB3
18 DB2
17 DB1
16 DB0 (LSB)
15
DIGITAL
COMMON DC
DIGITAL
DATA
OUTPUTS
PRODUCT DESCRIPTION
The AD674B and AD774B are complete 12-bit successive-
approximation analog-to-digital converters with three-state
output buffer circuitry for direct interface to 8- and 16-bit
microprocessor busses. A high-precision voltage reference and
clock are included on chip, and the circuit requires only power
supplies and control signals for operation.
The AD674B and AD774B are pin-compatible with the indus-
try standard AD574A, but offer faster conversion time and bus-
access speed than the AD574A and lower power consumption.
The AD674B converts in 15 µs (maximum) and the AD774B
converts in 8 µs (maximum).
The monolithic design is implemented using Analog Devices’
BiMOS II process allowing high-performance bipolar analog
circuitry to be combined on the same die with digital CMOS logic.
Offset, linearity, and scaling errors are minimized by active
laser trimming of thin-film resistors.
Five different grades are available. The J and K grades are
specified for operation over the 0°C to 70°C temperature range.
The A and B grades are specified from –40°C to +85°C, the T grade
is specified from –55°C to +125°C. The J and K grades are
available in a 28-lead plastic DIP or 28-lead SOIC. All other grades
are available in a 28-lead hermetically sealed ceramic DIP.
PRODUCT HIGHLIGHTS
1. Industry Standard Pinout: The AD674B and AD774B use
the pinout established by the industry standard AD574A.
2. Analog Operation: The precision, laser-trimmed scaling and
bipolar offset resistors provide four calibrated ranges: 0 V to
10 V and 0 V to 20 V unipolar; –5 V to +5 V and –10 V to
+10 V bipolar. The AD674B and AD774B operate on +5 V
and ± 12 V or ± 15 V power supplies.
3. Flexible Digital Interface: On-chip multiple-mode three-state
output buffers and interface logic allow direct connection to
most microprocessors. The 12 bits of output data can be
read either as one 12-bit word or as two 8-bit bytes (one with
8 data bits, the other with 4 data bits and 4 trailing zeros).
4. The internal reference is trimmed to 10.00 V with 1% maxi-
mum error and 10 ppm/°C typical temperature coefficient.
The reference is available externally and can drive up to
2.0 mA beyond the requirements of the converter and bipo-
lar offset resistors.
5. The AD674B and AD774B are available in versions compli-
ant with MIL-STD-883. Refer to the Analog Devices Mili-
tary Products Databook or current AD674B/AD774B/883B
data sheet for detailed specifications.
REV. C
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties that
may result from its use. No license is granted by implication or otherwise
under any patent or patent rights of Analog Devices.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700
www.analog.com
Fax: 781/326-8703
© Analog Devices, Inc., 2002







AD674B pdf, 数据表
AD674B/AD774B
Circuit layout should attempt to locate the ADC, associated
analog input circuitry, and interconnections as far as possible
from logic circuitry. For this reason, the use of wire-wrap circuit
construction is not recommended. Careful printed-circuit layout
and manufacturing is preferred.
UNIPOLAR RANGE CONNECTIONS FOR THE AD674B
AND AD774B
The AD674B and AD774B contain all the active components
required to perform a complete 12-bit A/D conversion. Thus,
for most situations, all that is necessary is connection of the
power supplies (+5 V, +12/+15 V, and 12/15 V), the analog
input, and the conversion initiation command, as discussed on
the next page.
OFFSET
R1
12V/ 100k+12V/
15V
+15V
GAIN
100k
R2
100
100
0 TO 10V
ANALOG
INPUTS
0 TO 20V
AD674B/AD774B
2 12/8
3 CS
4 A0
5 R/C
6 CE
10 REF IN
8 REF OUT
STS 28
HIGH BITS
2427
MIDDLE BITS
2023
LOW BITS
1619
12 BIP OFF
13 10VIN
14 20VIN
+5V 1
+15V 7
15V 11
9 ANA COM
DIG COM 15
Figure 7. Unipolar Input Connections
All of the thin-film application resistors of the AD674B and
AD774B are factory trimmed for absolute calibration. Therefore,
in many applications, no calibration trimming will be required.
The absolute accuracy for each grade is given in the specification
tables. For example, if no trims are used, ±2 LSB max zero offset
error and ± 0.25% (10 LSB) max full-scale error are guaranteed.
If the offset trim is not required, Pin 12 can be connected directly
to Pin 9; the two resistors and trimmer for Pin 12 are then not
needed. If the full-scale trim is not required, a 50 1% metal
film resistor should be connected between Pin 8 and Pin 10.
The analog input is connected between Pins 13 and 9 for a 0 V
to 10 V input range, between Pins 14 and 9 for a 0 V to 20 V
input range. Input signals beyond the supplies are easily accommo-
dated. For the 10 V span input, the LSB has a nominal value of
2.44 mV; for the 20 V span, 4.88 mV. If a 10.24 V range is
desired (nominal 2.5 mV/bit), the gain trimmer (R2) should be
replaced by a 50 resistor and a 200 trimmer inserted in
series with the analog input to Pin 13 (for a full-scale range of
20.48 V [5 mV/bit] use a 500 trimmer into Pin 14). The
gain trim described below is now done with these trimmers.
The nominal input impedance into Pin 13 is 5 k, and into Pin
14 is 10 k.
UNIPOLAR CALIBRATION
The connections for unipolar ranges are shown in Figure 7. The
AD674B or AD774B is trimmed to a nominal 1/2 LSB offset so
that the exact analog input for a given code will be in the middle
of that code (halfway between the transitions to the codes above
and below it). Thus, when properly calibrated, the first transition
(from 0000 0000 0000 to 0000 0000 0001) will occur for an input
level of +1/2 LSB (1.22 mV for 10 V range).
If Pin 12 is connected to Pin 9, the unit will behave in this manner,
within specifications. If the offset trim (R1) is used, it should be
trimmed as above, although a different offset can be set for a
particular system requirement. This circuit will give approximately
± 15 mV of offset trim range.
The full-scale trim is done by applying a signal 1 1/2 LSB below
the nominal full scale (9.9963 for a 10 V range). Trim R2 to
give the last transition (1111 1111 1110 to 1111 1111 1111).
BIPOLAR OPERATION
The connections for bipolar ranges are shown in Figure 8.
Again, as for the unipolar ranges, if the offset and gain specifica-
tions are sufficient, one or both of the trimmers shown can be
replaced by a 50 Ω ± 1% fixed resistor. The analog input is
applied as for the unipolar ranges. Bipolar calibration is similar
to unipolar calibration. First, a signal 1/2 LSB above negative
full scale (4.9988 V for the ± 5 V range) is applied and R1 is
trimmed to give the first transition (0000 0000 0000 to 0000
0000 0001). Then a signal 1 1/2 LSB below positive full scale
(+4.9963 V for the ± 5 V range) is applied and R2 trimmed to
give the last transition (1111 1111 1110 to 1111 1111 1111).
R2
GAIN
100
100
OFFSET
R1
؎5V
ANALOG
INPUTS
؎10V
AD674B/AD774B
2 12/8
3 CS
4 A0
5 R/C
6 CE
10 REF IN
STS 28
HIGH BITS
2427
MIDDLE BITS
2023
8 REF OUT
12 BIP OFF
LOW BITS
1619
+5V 1
13 10VIN
14 20VIN
+15V 7
15V 11
9 ANA COM
DIG COM 15
Figure 8. Bipolar Input Connections
GROUNDING CONSIDERATIONS
The analog common at Pin 9 is the ground reference point for
the internal reference and is thus the high qualityground for
the ADC; it should be connected directly to the analog reference
point of the system. To achieve the high-accuracy performance
available from the ADC in an environment of high digital noise
content, the analog and digital commons must be connected
together at the package. In some situations, the digital common
at Pin 15 can be connected to the most convenient ground ref-
erence point; digital power return is preferred.
–8– REV. C














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