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參數(shù)資料
| 型號： | ISO122 |
| 元件分類： | 隔離放大器 |
| 英文描述： | Precision Lowest Cost ISOLATION AMPLIFIER |
| 中文描述： | 成本最低的精密隔離放大器 |
| 文件頁數(shù)： | 6/15頁 |
| 文件大?。?/td> | 188K |
| 代理商： | ISO122 |
6
ISO122
THEORY OF OPERATION
The ISO122 isolation amplifier uses an input and an output
section galvanically isolated by matched 1pF isolating ca-
pacitors built into the plastic package. The input is duty-
cycle modulated and transmitted digitally across the barrier.
The output section receives the modulated signal, converts it
back to an analog voltage and removes the ripple component
inherent in the demodulation. Input and output sections are
fabricated, then laser trimmed for exceptional circuitry match-
ing common to both input and output sections. The sections
are then mounted on opposite ends of the package with the
isolating capacitors mounted between the two sections. The
transistor count of the ISO122 is 250 transistors.
MODULATOR
An input amplifier (A1, Figure 1) integrates the difference
between the input current (V
/200k
) and a switched
±
100
μ
A current source. This current source is implemented
by a switchable 200
μ
A source and a fixed 100
μ
A current
sink. To understand the basic operation of the modulator,
assume that V
= 0.0V. The integrator will ramp in one
direction until the comparator threshold is exceeded. The
comparator and sense amp will force the current source to
switch; the resultant signal is a triangular waveform with a
50% duty cycle. The internal oscillator forces the current
source to switch at 500kHz. The resultant capacitor drive is
a complementary duty-cycle modulation square wave.
DEMODULATOR
The sense amplifier detects the signal transitions across the
capacitive barrier and drives a switched current source into
integrator A2. The output stage balances the duty-cycle
modulated current against the feedback current through the
200k
feedback resistor, resulting in an average value at the
V
pin equal to V
. The sample and hold amplifiers in the
output feedback loop serve to remove undesired ripple
voltages inherent in the demodulation process.
BASIC OPERATION
SIGNAL AND SUPPLY CONNECTIONS
Each power supply pin should be bypassed with 1
μ
F tanta-
lum capacitors located as close to the amplifier as possible.
The internal frequency of the modulator/demodulator is set
at 500kHz by an internal oscillator. Therefore, if it is desired
to minimize any feedthrough noise (beat frequencies) from
a DC/DC converter, use a
π
filter on the supplies (see Figure
4). ISO122 output has a 500kHz ripple of 20mV, which can
be removed with a simple two pole low-pass filter with a
100kHz cutoff using a low cost op amp. See Figure 4.
The input to the modulator is a current (set by the 200k
integrator input resistor) that makes it possible to have an
input voltage greater than the input supplies, as long as the
output supply is at least
±
15V. It is therefore possible when
using an unregulated DC/DC converter to minimize PSR
related output errors with
±
5V voltage regulators on the
isolated side and still get the full
±
10V input and output
swing. An example of this application is shown in Figure
10.
CARRIER FREQUENCY CONSIDERATIONS
The ISO122 amplifier transmits the signal across the isola-
tion barrier by a 500kHz duty cycle modulation technique.
For input signals having frequencies below 250kHz, this
system works like any linear amplifier. But for frequencies
above 250kHz, the behavior is similar to that of a sampling
amplifier. The signal response to inputs greater than 250kHz
1pF
200
μ
A
100
μ
A
200k
Isolation Barrier
1pF
1pF
200
μ
A
100
μ
A
200k
V
IN
+
–
Osc
Gnd 1 –V
S1
+V
S1
V
OUT
S/H
G = 6
S/H
G = 1
Gnd 2
+V
S2
–V
S2
–
+
A2
Sense
Sense
FIGURE 1. Block Diagram.
A1
150pF
150pF
1pF
| |
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| ISO122JP | Precision Lowest Cost ISOLATION AMPLIFIER |
| ISO122JU | Precision Lowest Cost ISOLATION AMPLIFIER |
| ISO122P | Precision Lowest Cost ISOLATION AMPLIFIER |
| ISO122U | Precision Lowest Cost ISOLATION AMPLIFIER |
| ISO124 | Precision Lowest Cost ISOLATION AMPLIFIER |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| ISO122JP | 功能描述:隔離放大器 Precision Low Cost Isolation Amp RoHS:否 制造商:Texas Instruments 輸入補償電壓:1.5 mV 共模抑制比（最小值）:95 dB 帶寬:60 KHz 工作電源電壓:3.3 V 電源電流:8 mA 工作溫度范圍:- 40 C to + 105 C 安裝風格:SMD/SMT 封裝 / 箱體:SOP-8 封裝:Tube |
| ISO122JP | 制造商:Texas Instruments 功能描述:AMP PRECISION ISOLATION DIP16 122 |
| ISO122JPE4 | 功能描述:隔離放大器 Precision Low Cost Isolation Amp RoHS:否 制造商:Texas Instruments 輸入補償電壓:1.5 mV 共模抑制比（最小值）:95 dB 帶寬:60 KHz 工作電源電壓:3.3 V 電源電流:8 mA 工作溫度范圍:- 40 C to + 105 C 安裝風格:SMD/SMT 封裝 / 箱體:SOP-8 封裝:Tube |
| ISO122JU | 功能描述:隔離放大器 Precision Low Cost Isolation Amp RoHS:否 制造商:Texas Instruments 輸入補償電壓:1.5 mV 共模抑制比（最小值）:95 dB 帶寬:60 KHz 工作電源電壓:3.3 V 電源電流:8 mA 工作溫度范圍:- 40 C to + 105 C 安裝風格:SMD/SMT 封裝 / 箱體:SOP-8 封裝:Tube |
| ISO122JU | 制造商:Texas Instruments 功能描述:IC SM AMP ISOLATION |
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