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What is AD774B?

This electronic component, produced by the manufacturer "Analog Devices", performs the same function as "Complete 12-Bit A/D Converters".


AD774B Datasheet PDF - Analog Devices

Part Number AD774B
Description Complete 12-Bit A/D Converters
Manufacturers Analog Devices 
Logo Analog Devices Logo 


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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

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AD774B equivalent
AD674B/AD774B
DEFINITION OF SPECIFICATIONS
Linearity Error
Linearity error refers to the deviation of each individual code
from a line drawn from zerothrough full scale.The point
used as zerooccurs 1/2 LSB (1.22 mV for 10 V span) before
the first code transition (all zeroes to only the LSB on). Full
scaleis defined as a level 1 1/2 LSB beyond the last code tran-
sition (to all ones). The deviation of a code from the true straight
line is measured from the middle of each particular code.
The K, B, and T grades are guaranteed for maximum nonlinear-
ity of ± 1/2 LSB. For these grades, this means that an analog
value that falls exactly in the center of a given code width will
result in the correct digital output code. Values nearer the upper
or lower transition of the code width may produce the next upper
or lower digital output code. The J and A grades are guaranteed
to ± 1 LSB max error. For these grades, an analog value that
falls within a given code width will result in either the correct
code for that region or either adjacent one.
Note that the linearity error is not user adjustable.
Differential Linearity Error (No Missing Codes)
A specification that guarantees no missing codes requires that
every code combination appear in a monotonic increasing sequence
as the analog input level is increased. Thus every code must have a
finite width. The AD674B and AD774B guarantee no missing codes
to 12-bit resolution, requiring that all 4096 codes must be present
over the entire operating temperature ranges.
Unipolar Offset
The first transition should occur at a level 1/2 LSB above analog
common. Unipolar offset is defined as the deviation of the actual
transition from that point. This offset can be adjusted as discussed
later. The unipolar offset temperature coefficient specifies the
maximum change of the transition point over temperature,
with or without external adjustment.
Bipolar Offset
In the bipolar mode the major carry transition (0111 1111 1111
to 1000 0000 0000) should occur for an analog value 1/2 LSB
below analog common. The bipolar offset error and temperature
coefficient specify the initial deviation and maximum change in
the error over temperature.
Quantization Uncertainty
Analog-to-digital converters exhibit an inherent quantization
uncertainty of ± 1/2 LSB. This uncertainty is a fundamental
characteristic of the quantization process and cannot be reduced
for a converter of given resolution.
Left-Justified Data
The output data format is left-justified. This means that the
data represents the analog input as a fraction of full scale, rang-
ing from 0 to 4095/4096. This implies a binary point 4095 to
the left of the MSB.
Full-Scale Calibration Error
The last transition (from 1111 1111 1110 to 1111 1111 1111)
should occur for an analog value 1 1/2 LSB below the nominal
full scale (9.9963 V for 10.000 V full scale). The full-scale cali-
bration error is the deviation of the actual level at the last transi-
tion from the ideal level. This error, which is typically 0.05% to
0.1% of full scale, can be trimmed out as shown in Figures 7
and 8. The full-scale calibration error over temperature is given
with and without the initial error trimmed out. The temperature
coefficients for each grade indicate the maximum change in the
full-scale gain from the initial value using the internal 10 V
reference.
Temperature Drift
The temperature drift for full-scale calibration, unipolar offset,
and bipolar offset specifies the maximum change from the initial
(25°C) value to the value at TMIN or TMAX.
Power Supply Rejection
The standard specifications assume use of +5.00 V and ± 15.00 V
or ± 12.00 V supplies. The only effect of power supply error on
the performance of the device will be a small change in the
full-scale calibration. This will result in a linear change in all
low-order codes. The specifications show the maximum full-
scale change from the initial value with the supplies at the
various limits.
Code Width
A fundamental quantity for A/D converter specifications is the
code width. This is defined as the range of analog input values for
which a given digital output code will occur. The nominal value
of a code width is equivalent to 1 least significant bit (LSB) of the
full-scale range or 2.44 mV out of 10 V for a 12-bit ADC.
REV. C
–5–


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