USB hot plug

229

02:39:38

USB has 220uF (w/ ESR) on the host mother board, and the question is when I hot plug a device what is happening to the USB 5V power (over simplified but shows the idea).

Now that I have this simulating I can see  the current pulse peak and that it is much bigger with 10uF. Also a soft start idea.

Top is a soft start circuit.

Some Info from:
http://www.usb.org/developers/docs/whitepapers/power_delivery_motherboards.pdf

link back to Arduino forum:
http://forum.arduino.cc/index.php?topic=301436.0

published 9 years ago

usernames

9 years ago

Swap the 1 ohm resistor and the inductor around. It wont matter for the purposes of your circuit and it allows the simulator to separate the transient calculations of capacitor and inductor. To answer your real question, im not sure, if your computer is rebooting or locking up you might try different devices, maybe there is a short in the device you are plugging into it. If it does it with any device, its a weak computer power supply or one thats near its current limit. You could increase 1 ohm resistor to 3 to reduce max load.

flowDAQ

9 years ago

Swapped resistor and inductor, but simulation is still crashing. I was trying to see how much of a current spike from each capacitor.

flowDAQ

9 years ago

remove 220uF cap and switch to 5V supply that was used to charge and isolate it.

faceblast

9 years ago

cool info from Intel. from reading Intel's notes, looks like voltage drop like this can happen if the ESR is too high on the bypass cap.

flowDAQ

9 years ago

@faceblast that is a good point the 220uF capacitor ESR will cause a voltage drop that could take VUSB out of its required range and upset the FTDI chip also. The FT232RL datasheet shows a 4.7uF bypass capacitor, but a 10uF may be too much and either trip the resettable fuse or cause voltage to drop out of spec.

flowDAQ

9 years ago

add link back to arduino forum

flowDAQ

9 years ago

Sim works with ESR on 220uF capacitor

flowDAQ

9 years ago

Added soft start, just to have a look

Lucan01

9 years ago

Is there any way I can limit current to 1 amp?

flowDAQ

8 years ago

Slight mod to soft start that seems to help

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