microcontroller usb and PC usb port connexion design

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Hicham M

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Hello,

I'm developping a firmware for a custom board that has a usb in it.

This board had burned many usb ports in other computers.
I had a new workstation 6 months ago, and I already changed the motherboard and yesterday the power supply. all happened because of this board.

I attached here the schematic of the usb connexion in the board, it seems okey for me. I would appreciate it if anyone could take a look at it.

also, is there any tips or tricks to go through this problem and find out why my the usb port is burning my computer ?

Thank you
 

Put some resistors in 4 and 5th pin, its not good to give directly to a zener diode without resistor.

can you calculate, what is the current through the zener if you are giving 5.5v in the input?
 

Venkadesh_M said:
Put some resistors in 4 and 5th pin, its not good to give directly to a zener diode without resistor.

can you calculate, what is the current through the zener if you are giving 5.5v in the input?
Click to expand...

Thank you VenKadesh,

I also noticed the missing resistors too, but when I check the zener array datasheet, in their typical schematic , they didn't put resistors (check the page below )

I'll see how I can calculate the current.
 

One doubt,

this connector is not looking like Standard USB type connector........It's looks like RJ11 .....

Then you have custom cable for connecting.....CAn u elaborate little bit...
 

malli_1729 said:
One doubt,

this connector is not looking like Standard USB type connector........It's looks like RJ11 .....

Then you have custom cable for connecting.....CAn u elaborate little bit...
Click to expand...

Indeed, it's the same as the Ethernet connectors, goes with the RG45.

I build my cable using a standard cable (type A-B) and replacing the B connector with RG45 connector( I connect the 4 pins : D+,D-,Vdd and Vcc )

I tested the ground of the A connector and it is linked to the board's ground.

- - - Updated - - -

Venkadesh_M said:
if it is not advisable then select some more voltage zener. It should not be in the range of usb 4.5 to 5.5V.
Click to expand...

Sorry, I didn't understand ? you mean I should replace the zener array with one that supports higher voltage ?
 

Are you sure about the cabling.
USB is rather robust standard when it comes to short circuiting.
"According to the USB 2.0 specification, a USB transceiver is required to Withstand a continuous short circuit of D+ and/or D- to VBUS, ground, other data lines or the cable shield at the connector for a minimum of 24 hours Without causing damage to the internal circuitry."
"It is recommended that transceivers be designed to withstand such short-circuits indefinitely. The device must not be damaged under the
short-circuit condition when transmitting 50% of the time and receiving 50% of the time (in all supported speeds). The transmit phase consists of a symmetrical signal that toggles between drive HIGH and drive LOW. This requirement must be met for max value of VBUS (5.25 V). "
 

Venkadesh_M said:
select some zener of more than 5.5V. otherwise it may load the data lines.
Click to expand...

That's not an option, I have already 300 units in the field and I just want to protect my computer, We will report this to the hardward designer

- - - Updated - - -


Yes, I use the same cables to connect 150 tablet with the same electronic board, and I had like 10 cases where the usb ports where broke because of the board.
But in my case, I have the entire Motherboard changed???

I am not sure what I am doing wrong that get my PC broke so often.
Is there a way to test the robustness of my usb connexion ??
 

What controller or USB transceiver you are using ?

Is your self powered or powered from USB ?

if yes what is the current it is taking from the port ?

did you find any other faults with the target board after using long time ?
 


Hicham M said:
I'm using PIC 32MX

My target board is self powered by a power supply (24V/ 3A max)

No, just the fact that USB ports broke after a while in (%10 of the cases).
Click to expand...

Every thing looks ok other than the zener have a try on it.

did you use USB_UC_D_N anywhere else ? Why there is R44 and R45 ?

Also is Vbus going anywhere else other than Vbus of the controller ?
 

Venkadesh_M said:
Every thing looks ok other than the zener have a try on it.
Click to expand...

Venkadesh_M said:
did you use USB_UC_D_N anywhere else ? Why there is R44 and R45 ?
Click to expand...

Nope, USB_UC_D_N is not used else anywhere , I think R44 & R45 are recommanded in the microcontroller datasheet
Venkadesh_M said:
Also is Vbus going anywhere else other than Vbus of the controller ?
Click to expand...
Nope, striaght to the ucontroller


I just got my pc repaired, hope this will not happen again.
 

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