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The source is soft current limited to about 125mA or so. As for lightning, despite this circuit being connected to worlds longest lightning rod, we have never noticed any damage. In fact, the only part of our box that ever gets damaged is the RS-485 circuit. Yea, I working on that too.
Jeff Stout
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LOL
Jeff Stout
Aha, another factoid for the design. You mentioned thousands of drivers. Does each driver have its own dedicated source?
The 125mA limit could severely limit the output-signal slew rate into the cable's capacitance, where dV/dt = i/C tells us it'll take 72us to slew 6V with 125mA into a 1.5uF load (this assumes all of the 125mA is available for cable charging - how much is not available, being used up by the DC loads?) If we assume the same slew rate for load discharge, and provide some decent standing time with the voltage sitting HI and LO, you're looking at 300 to 400us minimum period, or 2400 baud maximum.
You had mentioned 9600 baud, but that'd be too fast. You can improve on the 12V/us slew rate by adding a say 10uF capacitor across the source and increasing the output current limit, at the expense of some source-voltage sag.
BTW, where does your 24V to 50V source range spec come from?
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Thanks,
- Win
That's makes things much easier since the maximum sustained power supply delivery under short circuit output will be 50 x 1/8= 6.25W, so that using your original 220 emitter follower pullup resistor, the power supply output would droop to Vo/220 + Vo/4.7= 0.125 or a Vbe or so. A short to Vcc turns the driver off- depending on which circuit:-)
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