AD574A
+VS
page. Analog input connections and calibration are easily ac-
complished; the unipolar operating mode is shown in Figure 4.
+15V
+5V
+
+
TO A1
C1
C2
+
C3
A
VREF
–VS
–15V
AGND
TO A1
12/8
2
28
STS
11
1
2 6 7
3
4
5
CS
AO
+VS
OFFSET
R1
100k
8
27
24
23
20
19
16
HIGH
BIT
R2
100Ω
12-BIT
3-STATE
DATA
14 13 12 11 10
9
8
+12V/+15V
GAIN
–12V/–15V
10
13
R/C
10k 10k
GAIN
MIDDLE
BITS
27
A2
6
CE
100pF
+15V
R1
100k
OFFSET
R4
100k
AD574A
AD574A
LOW
BITS
16
12
9
100k
A1
AD585
10
8
REF IN
R2
100Ω
R3
100Ω
–15V
REF OUT
3
4
1
2
3
4
5
6
7
100Ω
12 BIP OFF
15
–VS
ANALOG
INPUT
0V TO +10V
28
5
A
1
0 TO +10V
+5V
+15V
–15V
13 10VIN
14 20VIN
STATUS
ANALOG
INPUTS
7
CONVERT
7404 OR EQ.
NOTE
11
1. C1, C2, C3 ARE 47F TANTALUM, BYPASSED BY
0.1µF CERAMIC. LOCATE AT ASSOCIATED A2 PINS.
µ
0 TO +20V
15
DIG COM
ANA COM
9
Figure 3. AD574A with AD585 Sample and Hold
SUPPLY DECOUPLING AND LAYOUT
CONSIDERATIONS
Figure 4. Unipolar Input Connections
It is critically important that the AD574A power supplies be fil-
tered, well regulated, and free from high frequency noise. Use of
noisy supplies will cause unstable output codes. Switching
power supplies are not recommended for circuits attempting to
achieve 12-bit accuracy unless great care is used in filtering any
switching spikes present in the output. Remember that a few
millivolts of noise represents several counts of error in a 12-bit
ADC.
All of the thin-film application resistors of the AD574A are
trimmed for absolute calibration. Therefore, in many applica-
tions, 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, the AD574AK guarantees
±1 LSB max zero offset error and ±0.25% (10 LSB) max
full-scale error. (Typical full-scale error is ±2 LSB.) 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 needed, a 50 Ω ± 1% metal film resistor
should be connected between Pin 8 and Pin 10.
Decoupling capacitors should be used on all power supply pins;
the +5 V supply decoupling capacitor should be connected
directly from Pin 1 to Pin 15 (digital common) and the +VCC
and –VEE pins should be decoupled directly to analog common
(Pin 9). A suitable decoupling capacitor is a 4.7 µF tantalum
type in parallel with a 0.1 µF disc ceramic type.
The analog input is connected between Pin 13 and Pin 9 for a
0 V to +10 V input range, between 14 and Pin 9 for a 0 V to
+20 V input range. The AD574A easily accommodates an input
signal beyond the supplies. For the 10 volt span input, the LSB
has a nominal value of 2.44 mV; for the 20 volt 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 Ω resistor, and a
200 Ω 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 Ω trim-
mer into Pin 14. The gain trim described below is now done
with these trimmers. The nominal input impedance into Pin 13
is 5 kΩ, and 10 kΩ into Pin 14.
Circuit layout should attempt to locate the AD574A, 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 con-
struction is preferred.
GROUNDING CONSIDERATIONS
The analog common at Pin 9 is the ground reference point for
the internal reference and is thus the “high quality” ground for
the AD574A; it should be connected directly to the analog refer-
ence point of the system. In order to achieve all of the high
accuracy performance available from the AD574A in an envi-
ronment of high digital noise content, the analog and digital
commons should be connected together at the package. In some
situations, the digital common at Pin 15 can be connected to
the most convenient ground reference point; analog power
return is preferred.
UNIPOLAR CALIBRATION
The AD574A is intended to have 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, 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 man-
ner, 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 ap-
proximately ±15 mV of offset trim range.
UNIPOLAR RANGE CONNECTIONS FOR THE AD574A
The AD574A contains all the active components required to
perform a complete 12-bit A/D conversion. Thus, for most situ-
ations, all that is necessary is connection of the power supplies
(+5 V, +12 V/+15 V and –12 V/–15 V), the analog input, and
the conversion initiation command, as discussed on the next
REV. B
–7–
5秒后页面跳转
STM32F030C6芯片介绍：主要参数分析、引脚配置说明、功耗及封装
PCF8591数据手册解读：参数、引脚说明
一文带你了解ss8050参数、引脚配置、应用指南
深入解析AD7606高性能多通道模数转换器：资料手册参数分析
微信公众号
抖音公众号
浙公网安备 33010502006866号 浙ICP备10014259号-119
营业执照ICP证
技术参数
数据手册
如果您发现信息不准确，
