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AD526 Schematic ( PDF Datasheet ) - Analog Devices

Teilenummer AD526
Beschreibung Software Programmable Gain Amplifier
Hersteller Analog Devices
Logo Analog Devices Logo 




Gesamt 14 Seiten
AD526 Datasheet, Funktion
a
Software Programmable
Gain Amplifier
AD526
FEATURES
Digitally Programmable Binary Gains from 1 to 16
Two-Chip Cascade Mode Achieves Binary Gain from
1 to 256
Gain Error:
0.01% Max, Gain = 1, 2, 4 (C Grade)
0.02% Max, Gain = 8, 16 (C Grade)
0.5 ppm/؇C Drift Over Temperature
Fast Settling Time
10 V Signal Change:
0.01% in 4.5 s (Gain = 16)
Gain Change:
0.01% in 5.6 s (Gain = 16)
Low Nonlinearity: ؎0.005% FSR Max (J Grade)
Excellent DC Accuracy:
Offset Voltage: 0.5 mV Max (C Grade)
Offset Voltage Drift: 3 V/؇C (C Grade)
TTL-Compatible Digital Inputs
PIN CONFIGURATION
DIG GND 1
16 A1
NULL 2
15 A0
VIN 3
14 CS
NULL 4 AD526 13 CLK
TOP VIEW
ANALOG GND 2 5 (Not to Scale) 12 A2
ANALOG GND 1 6
11 B
–VS 7
VOUT SENSE 8
10 +VS
9 VOUT FORCE
PRODUCT DESCRIPTION
The AD526 is a single-ended, monolithic software program-
mable gain amplifier (SPGA) that provides gains of 1, 2, 4, 8
and 16. It is complete, including amplifier, resistor network
and TTL-compatible latched inputs, and requires no external
components.
Low gain error and low nonlinearity make the AD526 ideal for
precision instrumentation applications requiring programmable
gain. The small signal bandwidth is 350 kHz at a gain of 16. In
addition, the AD526 provides excellent dc precision. The FET-
input stage results in a low bias current of 50 pA. A guaranteed
maximum input offset voltage of 0.5 mV max (C grade) and low
gain error (0.01%, G = 1, 2, 4, C grade) are accomplished using
Analog Devices’ laser trimming technology.
To provide flexibility to the system designer, the AD526 can be
operated in either latched or transparent mode. The force/sense
configuration preserves accuracy when the output is connected
to remote or low impedance loads.
The AD526 is offered in one commercial (0°C to +70°C) grade,
J, and three industrial grades, A, B and C, which are specified
from –40°C to +85°C. The S grade is specified from –55°C to
+125°C. The military version is available processed to MIL-
STD 883B, Rev C. The J grade is supplied in a 16-lead plastic
DIP, and the other grades are offered in a 16-lead hermetic
side-brazed ceramic DIP.
APPLICATION HIGHLIGHTS
1. Dynamic Range Extension for ADC Systems: A single
AD526 in conjunction with a 12-bit ADC can provide
96 dB of dynamic range for ADC systems.
2. Gain Ranging Preamps: The AD526 offers complete digital
gain control with precise gains in binary steps from 1 to 16.
Additional gains of 32, 64, 128 and 256 are possible by cas-
cading two AD526s.
ORDERING GUIDE
Model
Temperature Package
Range
Descriptions
Package
Options
AD526JN
Commercial
AD526AD
Industrial
AD526BD
Industrial
AD526CD
Industrial
AD526SD
Military
AD526SD/883B
Military
5962-9089401MEA* Military
16-Lead Plastic DIP N-16
16-Lead Cerdip D-16
16-Lead Cerdip D-16
16-Lead Cerdip D-16
16-Lead Cerdip D-16
16-Lead Cerdip D-16
16-Lead Cerdip D-16
*Refer to official DESC drawing for tested specifications.
REV. D
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
which 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 World Wide Web Site: http://www.analog.com
Fax: 781/326-8703
© Analog Devices, Inc., 1999






AD526 Datasheet, Funktion
AD526
Figure 19. Large Signal Pulse
Response and Settling Time,* G = 8
Figure 20. Small Signal Pulse
Response, G = 8
Figure 21. Large Signal Pulse
Response and Settling Time,* G = 16
Figure 22. Small Signal Pulse
Response, Gain = 16
–60
–70
–80
–90
–100
10
100 1k 10k
FREQUENCY – Hz
100k
Figure 23. Total Harmonic Distortion
vs. Frequency Gain = 16
10
5
0
–5
–10
10
100 1k 10k
FREQUENCY – Hz
100k
Figure 24. Phase Distortion vs.
Frequency, Gain = 16
100
G = 4, 16
10
G = 2, 8
G=1
1
10k 100k 1M
FREQUENCY – Hz
10M
Figure 25. Output Impedance vs.
Frequency
Figure 26. Gain Change Settling
Time,** Gain Change: 1 to 2
Figure 27. Gain Change Settling
Time,** Gain Change 1 to 4
*For Settling Time Traces, 0.01% = 1/2 Vertical Division
**Scope Traces are: Top: Output Transition; Middle: Output Settling; Bottom: Digital Input.
–6–
REV. D

6 Page









AD526 pdf, datenblatt
AD526
FLOATING-POINT CONVERSION
High resolution converters are used in systems to obtain high
accuracy, improve system resolution or increase dynamic range.
There are a number of high resolution converters available with
throughput rates of 66.6 kHz that can be purchased as a single
component solution; however in order to achieve higher through-
put rates, alternative conversion techniques must be employed.
A floating point A/D converter can improve both throughput
rate and dynamic range of a system.
In a floating point A/D converter (Figure 42), the output data is
presented as a 16-bit word, the lower 12 bits from the A/D
converter form the mantissa and the upper 4 bits from the digi-
tal signal used to set the gain form the exponent. The AD526
programmable gain amplifier in conjunction with the compara-
tor circuit scales the input signal to a range between half scale
and full scale for the maximum usable resolution.
The A/D converter diagrammed in Figure 42 consists of a pair
of AD585 sample/hold amplifiers, a flash converter, a five-range
programmable gain amplifier (the AD526) and a fast 12-bit A/D
converter (the AD7572). The floating-point A/D converter
achieves its high throughput rate of 125 kHz by overlapping the
acquisition time of the first sample/hold amplifier and the set-
tling time of the AD526 with the conversion time of the A/D
converter. The first sample/hold amplifier holds the signal for
the flash autoranger, which determines which binary quantum
the input falls within, relative to full scale. Once the AD526 has
settled to the appropriate level, then the second sample/hold
amplifier can be put into hold which holds the amplified signal
while the AD7572 perform its conversion routine. The acquisi-
tion time for the AD585 is 3 µs, and the conversion time for the
AD7572 is 5 µs for a total of 8 µs, or 125 kHz. This performance
relies on the fast settling characteristics of the AD526 after the
flash autoranging (comparator) circuit quantizes the input sig-
nal. A 16-bit register holds the 3-bit output from the flash autor-
anger and the 12-bit output of the AD7572.
The A/D converter in Figure 42 has a dynamic range of 96 dB.
The dynamic range of a converter is the ratio of the full-scale
input range to the LSB value. With a floating-point A/D con-
verter the smallest value LSB corresponds to the LSB of the
monolithic converter divided by the maximum gain of the PGA.
The floating point A/D converter has a full-scale range of 5 V, a
maximum gain of 16 V/V from the AD526 and a 12-bit A/D
converter; this produces:
LSB = ([FSR/2N]/Gain) = ([5 V/4096]/16) = 76 µV. The
dynamic range in dBs is based on the log of the ratio of the
full-scale input range to the LSB; dynamic range = 20 log
(5 V/76 µV) = 96 dB.
+5V
CLOCK
125MHz
+5V
1 1/6
3 1/6
24
30pF 50k
74- +5V
123
1/2
1s
–15V +15V
10F+
VIN
–15V +15V
S/H
AD585
10F+
+
10F
+5V
F
AD526 S
VIN
B
A0 A1 A2
10F +
+
10F
–15V +15V
S/H
AD585
10k
10F+
+
10F
–15V +15V
BUSY
MSB
+10F
5 1/6 6
68pF
2.5MHz
68pF
VIN
AD7572
47F
LSB
10k
10F
–15V +15V
+10F
AD588
+5VREF
10k
5k
2.5k
1F 1.25k
1.25k
+5V
10k
10k
10k
10k
LM339A
74ALS86
13
2 1/4
12 11
13 1/4
4
5
6
1/4
98
10 1/4
1
2
3
1/4
11 10
1/6
A0
A1
A2
NOTE: ALL BYPASS CAPACITORS ARE 0.1F
+5V
74–
LS174
D12
D11
D10
D9
D8
D7
74–
LS174
D6
D5
D4
D3
D2
D1
74–
LS174
E1
E2
E3
Figure 42. Floating-Point A/D Converter
–12–
REV. D

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