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from IPython import display

New 8861 Design

First do the 8861 Sim

Some sim issues a small change to the Schotky diode means big changes to sim, both in results and sim speed. One Schotky choice didn't sim. Ended up with the RSX201VYM30 as I couldn't find a model for Charlie's choice.

First Try DC Vset (charlie_partB_02.asc)

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Appears to work. About 2 minutes to simulate. 2 volts on VSet. Sim as 900ma peak. Ripple current about 210ma. With 0.1 Rset should be about, $$I_{avg} = 2.0/2.5)\cdot(1.0)$$ $$I_{avg} = 800ma$$ and according to the sim is, $$I_{avg-sim} = 900 - (210/2)$$ $$I_{avg-sim} = 795ma$$

See image below.

Note: The 'Gear' method was used for the simulation.

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So it looks like the sim is working well.

Now try PWM Vset (charlie_partB_03.asc)

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Looks good. Set PWM freq at 25Khz, duty cycle 50%. Result shows average current approximately 500ma. VSet shown in blue.

There is a sub nanosecond multi amp glitch occasionally. I'm guessing it's a model/simulator glitch.

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Had to change the LTSpice settings as shown for an RC front end to VSet to simulate.

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Tried to determine the input impedance of Vset by putting a 100 ohm in series the the 2V source and measuring the drop. Apparently this failed as the Vset pin is higher than the 2V input ..

2V source is green, the Vset pin is blue.

Now Test the Analog Section

PWM Change

Image Schematic

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From 12% to 88%.

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Ripple about 20mv at 88%.