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Teilenummer | 3656 |
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Beschreibung | Transformer Coupled ISOLATION AMPLIFIER | |
Hersteller | Burr-Brown Corporation | |
Logo | ||
Gesamt 17 Seiten ® 3656
Transformer Coupled
ISOLATION AMPLIFIER
FEATURES
q INTERNAL ISOLATED POWER
q 8000V ISOLATION TEST VOLTAGE
q 0.5µA MAX LEAKAGE AT 120V, 60Hz
q 3-PORT ISOLATION
q IMR: 125dB REJECTION AT 60Hz
q 1" x 1" x 0.25" CERAMIC PACKAGE
DESCRIPTION
The 3656 was the first amplifier to provide a total
isolation function, both signal and power isolation, in
integrated circuit form. This remarkable advancement
in analog signal processing capability was accom-
plished by use of a patented modulation technique and
miniature hybrid transformer.
Versatility and performance are outstanding features
of the 3656. It is capable of operating with three
APPLICATIONS
q MEDICAL
Patient Monitoring and Diagnostic
Instrumentation
q INDUSTRIAL
Ground Loop Elimination and
Off-ground Signal Measurement
q NUCLEAR
Input/Output/Power Isolation
completely independent grounds (three-port isolation).
In addition, the isolated power generated is available
to power external circuitry at either the input or
output. The uncommitted op amps at the input and the
output allow a wide variety of closed-loop configura-
tions to match the requirements of many different
types of isolation applications.
Input
Demodulator
Pulse
Generator
+
–
Input
ISO
Power
Modulator
Rectifiers
and
Filters
Output
Demodulator
Rectifiers
and
Filters
Output
ISO
Power
SBOS132
This product is covered by the following United States patents: 4,066,974; 4,103,267; 4,082,908. Other patents pending may also apply upon the
allowance and issuance of patents thereon. The product may also be covered in other countries by one or more international patents corresponding
to the above-identified U.S. patents.
InternationalAirportIndustrialPark • MailingAddress:POBox11400,Tucson,AZ85734 • StreetAddress:6730S.TucsonBlvd.,Tucson,AZ 85706 • Tel:(520)746-1111 • Twx:910-952-1111
Internet:http://www.burr-brown.com/ • FAXLine:(800)548-6133(US/CanadaOnly) • Cable:BBRCORP • Telex:066-6491 • FAX:(520)889-1510 • ImmediateProductInfo:(800)548-6132
©1987 Burr-Brown Corporation
PDS-1403G
3656Printed in U.S.A. January, 1997
®
THEORY OF OPERATION
Details of the 3656 are shown in Figure 1. The external
connections shown, place it in its simplest gain configura-
tion —unity gain, noninverting. Several other amplifier gain
configurations and power isolation configurations are
possible. See Installation and Operating Instructions and
Applications sections for details.
Isolation of both signal and power is accomplished with a
single miniature toroid transformer with multiple windings.
A pulse generator operating at approximately 750kHz pro-
vides a two-part voltage waveform to transformer, T1. One
part of the waveform is rectified by diodes D1 through D4 to
provide the isolated power to the input and output stages
(+V, –V and V+, V–). The other part of the waveform is
modulated with input signal information by the modulator
operating into the V2 winding of the transformer.
The modulated signal is coupled by windings W6 and W7 to
two matched demodulators—one in the input stage and one
in the output stage—which generate identical voltages at
their outputs, pins 10 and 11 (Voltages identical with respect
to their respective commons, pins 3 and 17). In the input
stage the input amplifier, A1, the modulator and the input
demodulator are connected in a negative feedback loop. This
forces the voltage at pin 6 (connect as shown in Figure 1) to
equal the input signal voltage applied at pin 7. Since the
input and the output demodulators are matched and produce
identical output voltages, the voltage at pin 11 (referenced to
pin 17, the output common) is equal to the voltage at pin 10
(referenced to pin 3, the input common). In the output stage,
output amplifier A2 is connected as a unity gain buffer, thus
the output voltage at pin 15 equals the output demodulator
voltage at pin 11. The end result is an isolated output voltage
at pin 15 equal to the input voltage at pin 7 with no galvanic
connection between them.
Several amplifier and power connection variations are pos-
sible:
1. The input stage may be connected in various operational
amplifier gain configurations.
2. The output stage may be operated at gains above unity.
3. The internally generated isolated voltages which provide
power to A1 and A2 may be overridden and external
supply voltages used instead.
Versatility and its three independent isolated grounds allow
simple solutions to demanding analog signal conditioning
problems. See the Installation and Operating Instructions
and Applications sections for details.
INSTALLATION AND
OPERATING INSTRUCTIONS
The 3656 is a very versatile device capable of being used in
a variety of isolation and amplification configurations. There
are several fundamental considerations that determine con-
figuration and component value constraints:
1. Consideration must be given to the load placed on the
resistance (pin 10 and pin 11) by external circuitry. Their
output resistance is 100kΩ and a load resistor of 2MΩ or
greater is recommended to prevent a voltage divider
loading effect in excess of 5%.
5 10
BAL
BAL
86
100kΩ 7
1
+V
+
VIN
–
4
–V
3
Input
Demodulator
W6
92
A1 Modulator
T1
Pulse
W1 Generator
P+ 19
P– 20
0.47µF
+
15VDC
–
14
Output
W7 Demodulator 11 13
100kΩ
15
A2
+
VOUT
D1
W2
W3
D2
V+
16
0.47µF
D3 D4
W4 W5
V–
12
0.47µF
–
17
FIGURE 1. Block Diagram.
®
3656
6
6 Page R3
3MΩ
R2
100kΩ
LA
330kΩ
1W
R1
11kΩ(2)
OPA177
R4
330kΩ
6
9
2
10
D
M
3MΩ
1µF
14
D
A2
1N4148s
15
68MΩ(1)
22pF
100MΩ(4)
High
330kΩ
RA 1W
D1
D3
RL
1N4148s 300kΩ
7
D2
D4
24V
0.5W
A1
4
1
3
I/P PWR
11
17
16
12
13
0.47µF(3)
O/P PWR
Pulse GEN
20
19
0.47µF
Low
100kΩ
+
15VDC
–
NOTES: (1) Bandpass 0.05Hz to 100Hz. (2) Adjustable resistor may be used to achieve max common-mode
rejection between LA /RA and RL.(3) Negative 15V supply may be connected in place of 0.47µF capacitor if available.
(4) See offset trimming section.
FIGURE 6. ECG Amplifier.
+V
D1
LA 330kΩ
D2
–V
+V
1/2
OPA1013
–V
3MΩ
300kΩ
R1
20kΩ
6
+V
D3
RA 330kΩ
D4
–V
VO
R4
id
+V
1/2
OPA1013
–V
R3
+V
OPA177
–V
R2
20kΩ
270kΩ
7
100kΩ
3MΩ
FIGURE 7. Driven Right-Leg Amplifier.
®
3656
9
2
10
D
M
14
D
A1
3656
3
1
+V
4
24V
0.5W
–V
D1 = D2 = D3 = D4 = 1N459
15
A2
20
17
13
16
19
11
12
3MΩ
0.1µF
0.1µF
+–
15VDC
12
High
Out
Low
Out
12 Page | ||
Seiten | Gesamt 17 Seiten | |
PDF Download | [ 3656 Schematic.PDF ] |
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