EternityForest
Member
Hello all, I've been pretty busy with stuff outside of electronics but recently I have been working on a design that needs to run from 0-32V and also needs to be hot-pluggable(It's a general purpose props/animatronics/lighting/sensors/control board).
The problem I've been having in the simulations is that stray inductance combined with inrush into the capacitors keeps pushing the voltage at the input of my switcher 5-25 volts over the supply for a few milliseconds when I hot plug it(in the simulation).
Since I don't want to use a grossly overprovisioned regulator, and I want to keep the parts count and cost down, and I would rather not use any aluminum capacitors
(size,lifetime,temperature range), the solution I am thinking of is to use a low-side switch on the power input, bypassed with a 4.7-22 ohm precharge resistor. Then I would put one of those little voltage-detect supervisors to detect when the DC-DC converter output is stable, and turn on the low side switch a few milliseconds later after the capacitor has had time to charge fully.
I'm also a little worried about hot UNplug transients caused by someone unplugging a board while it is drawing current but the input cap should be able to absorb that because the boards are pretty low power.
I was going to use one of ON semi's protected mosfets to avoid any ESD issues(This is going to be an open source design and I don't want to include any difficult to work with parts)
So what do you think? Is this a valid idea? I'm pretty sure it will work but i want to know if there are any issues I am not aware of.
The problem I've been having in the simulations is that stray inductance combined with inrush into the capacitors keeps pushing the voltage at the input of my switcher 5-25 volts over the supply for a few milliseconds when I hot plug it(in the simulation).
Since I don't want to use a grossly overprovisioned regulator, and I want to keep the parts count and cost down, and I would rather not use any aluminum capacitors
(size,lifetime,temperature range), the solution I am thinking of is to use a low-side switch on the power input, bypassed with a 4.7-22 ohm precharge resistor. Then I would put one of those little voltage-detect supervisors to detect when the DC-DC converter output is stable, and turn on the low side switch a few milliseconds later after the capacitor has had time to charge fully.
I'm also a little worried about hot UNplug transients caused by someone unplugging a board while it is drawing current but the input cap should be able to absorb that because the boards are pretty low power.
I was going to use one of ON semi's protected mosfets to avoid any ESD issues(This is going to be an open source design and I don't want to include any difficult to work with parts)
So what do you think? Is this a valid idea? I'm pretty sure it will work but i want to know if there are any issues I am not aware of.
