Hi team,
I would like to protect USB3.0 high speed bus from short to battery(<21V) fault.
If I place AC coupling capacitor in between USB connector and TUSB501-Q1 input(and output), does it protect TUSB501-Q1 from short to battery?
regards,
Hi Shinji,
You need to have 100nF AC coupling capacitors on the TX outputs of the 501-Q1 to preserve the signals integrity. These will not protect from environmental overvoltage or short to battery faults. You will need Electrostatic Discharge (ESD) protection on the connector side for environmental static. This could be a diode that shorts the bus to ground when a high voltage is detected, like the TPD2E2U06-Q1.
For a short to battery fault. You would need over voltage protection (OVP). You could try using a USB MUX like the HD3SS3212-Q1 that switches off the USB bus when a fault is detected.
Best,
Shane
Hi Shinji,
After reviewing with my team, I think there is a solution. You could use an AC capacitor to block the DC component of a short to battery fault, however the original pulse will still get through. If you put an ESD diode between the capacitor and the device, this could protect the device from that pulse.
You would also need a 1 or 2 ohm resistor between the ESD diode and the device to protect the 501 from incoming current. Note that this resistance may slightly affect your signal integrity. For the diode, you need a clamping voltage above 3.2V as this is the common mode voltage plus the upper voltage swing on the TX line (2.55 + 0.65)V.
Your ESD diode should clamp above 3.2V but as close to this value as possible so the device isn’t damaged. You want to make sure both the AC capacitor and the ESD diode can handle 21V. The breakdown voltage for these devices must be 21V or higher.
Best,
Shane
