![]() ![]() His further interests are Internet of Things and Embedded Systems programming. LT1930A Demo Circuit - 1A, 1.2MHz, Step-up DC/DC Converter (5V to 12V 300mA) LTspice provides macromodels for most of Analog Devices’ switching regulators, linear regulators, and amplifiers, as well as a library of devices for general circuit simulation. Currently he works as an RF design engineer. LT1615 Demo Circuit - Power SEPIC Converter (2.5-4.2V to 3.3V 50mA) LT1930. He can be reached at Häring received his Master’s Degree in Electrical and Computer Engineering at Grand Valley State University in 2019 where he worked with Prof. Adamczyk is the author of the textbook “Foundations of Electromagnetic Compatibility with Practical Applications” (Wiley, 2017). He is an iNARTE certified EMC Master Design Engineer. Bogdan Adamczyk is professor and director of the EMC Center at Grand Valley State University () where he develops EMC educational material and teaches EMC certificate courses for industry. Bogdan Adamczyk, Foundations of Electromagnetic Compatibility with Practical Applications, Wiley, 2017.ĭr. EMC engineers are often called on to design low-pass filters for client projects, which is usually required to meet radiated susceptibility tests.Paul, Introduction to Electromagnetic Compatibility, Wiley, 2006. The measured results clearly show that, over the entire frequency range, the LC filter (inductor on the low impedance side and capacitor on the high impedance side) has a higher insertion loss than the CL filter (capacitor on the low impedance side and inductor on the high impedance side). These resonances were not predicted by the simulation models, as those models assumed ideal components and did not account for the board parasitics. A second resonance occurs at 60 MHz with the insertion loss of 83 dB for the CL filter and 95.5 dB for the LC filter. They will simulate at a higher value - probably set for the typical value of 2M 2 M. The measured results show the self-resonant frequency at 30 MHz, with the insertion loss of 84.9 dB for the CL filter and 115 dB for the LC filter. The LM741 input specification clearly states that these parts can have an input impedance as low as 300k 300 k. Table 2: Simulated and measured insertion loss for LC filterĪt 10 MHz the difference between the simulated insertion losses of the two filters is 15.1 dB which is close to the measured difference of 16.7 dB. Table 1: Simulated and measured insertion loss for CL filter LC Filter In the frequency range 100kHz – 10 MHz the simulated and measured results are remarkably close, as summarized in Tables 1 and 2. What are your preferred caps for this kind of application? I can redesign my board a bit to cope with larger caps if necessary (currently it can fit 2x25mm diameter caps with the resistors in between).Figure 12: Insertion loss (s 21 and s 34) measurements of the two configurations shown in Figure 8Ĭlearly, the LC filter outperforms the CL filter, which is consistent with the simulation results. Mouser doesn't have anything resembling the UPW type I'd like to use (long life, low impedance, high temp) at 10,000uF 35v in the leaded type. The caps I've chosen are Nichicon UKW 35V, which have a ripple current rating of 3.7A. I notice that by removing the PI filter resistors, this current reduces to 8A, but the ripple waveform is much sharper. I do have an NTC thermistor pre-transformer for inrush limitation. ![]() Is this correct and normal, or will it quickly degrade the smoothing caps (at least C1 and C7)? The spikes last around 1.5ms. The sim shows just under 80A immediately, quickly settling to around 11A spikes per half wave. My question regards the current at C1/C7. According to the LTSpice sim, this gives about 600mV of ripple at just over 28V. It's full bridge rectified per rail, using 2x10,000uF caps for smoothing. The load circuit is borrowed from post 12 in this thread, as LTSpice doesn't have a LM3886 model included as standard, so this may skew things a bit! I'm new to LTSpice, but thought the PSU circuit would be a good candidate for a first circuit to sim, so I've modelled it as per my schematic using 2 AC voltage sources running at 50Hz, around 29.5v to emulate the max output from a split secondary 18v toroidal transformer (UK mains). I'm designing an amp based on the LM3886 (I have a separate thread covering this over in Chip Amps), and with it a power supply for delivering +/- 28v-or-so.
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