11/13/2023 0 Comments Analog opto isolator![]() ![]() This TVS is rated for 600W peak pulse power capability at 10/1000μs wave meaning 58V 10.4A. The TVS incremental resistance, Zs at 58V = 1.3 Ω min. However if this results in a high slew rate current, circuit layout and filters mus prevent crosstalk to nearby high impedance isolated outputs that are unbalanced. In order to attenuate the input applied pulse, the input transient must have an impedance much higher than the TVS. To measure peak pulse power, the voltage and the current must both be measured and the peaks multiplied together to get the peak pulse power. They are either voltage or current waveforms. Note that these waveforms are not power waveforms. Sometimes it is defined by Voc and other times by Isc, short-cct.īoth modes have been supported by TVS's due to very high dynamic range (10A), fast response time and low resistance. The test requirements are often dictated by Industry safety standards 1st then regional standards, then national std. The wave is defined by the Vpk, Tr, Td or sometimes Isc. Often power transformers can pass thru this voltage if the level exceeds the supply protection or is capacitively coupled or the impulse might be induced via the building lightning rod current travelling down (hopefully) not too near the elevator shaft.Ī long elevator sensor-cable looks like a great antenna, so low impedance and filters are needed to attenuate RF and surge impulse noise but not too low that it conducts 100A! AC powered industry uses shorter transients (with lower impedance) which are often tested with 8 x 20 us surge impulses. A standard waveform used in telephone circuits is a 10 x 1000 μs waveform meaning 10 μs rise time and 1000 μs tail decay time to 50% V. These waveforms are called double exponential waveforms. Peak pulse power ratings are measured by using laboratory-generated pulses that are designed to simulate pulses on cables caused by nearby lightning strikes. Basically, a good design but might still cause glitches. A complete analysis is not possible without geometric layout. But this can lead to crosstalk with leakage crosstalk current. The TVS acts a brute force 600W absorbing bipolar zener. But feel free to tell ask another question with more background design info.īut the CA type TVS is a special dual zener back-back diode. The result is a reasonably good analog signal transmission with most of the non-linearities ironed out.I will not have time to explain everything. The result is that the output voltage matches the input voltage. Meanwhile on the output side the photo-diode's output current (which is the same as that on the input side) flows through R18 which is also 100 kΩ. Note that on the input side R17, 100 kΩ, determines the input current from V3 to the virtual ground and out to the feedback photo-diode. Inverting op-amp amplifier's input current all ends up in the feedback element (because the inputs have extremely high impedance) and the result is that both U5 and U6 have "identical" currents running in their inputs and feedback loops so the U6 output voltage = V3.įigure 2. ![]() The lower right photo-diode will then have the same current which will be fed into U6. This causes the transmitter op-amp output to adjust the current through U4's LED (top) so that the required current is fed back from the left photo-diode. The idea here is that the bottom left photo-diode is inserted into the transmitter's feedback loop. When an analog signal requires opto-isolation a common trick is to use a device with one LED and two matched photo-diodes arranged to receive the same amount of irradiance from the LED. This is true of the LED and of the photo-receptor - whether photo-diode or photo-transistor. ![]()
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