AD2 Short Circuit

[Igor Luiz]

Hi everyone,

I´ve been using AD2 for a while and I know the limitations about ground and the issues related to using the BNC adapter board.

Today I´ve made a big mistake, I haven't paid attention so some details and now my AD2 is dead.

I was working with my AD2 connected and a micro controller programmer connected to the same USB hub, developing some firmware changes in a device that I was scoping. I was interesting in evaluating the current consumption using a shunt resistor in a power supply used to power the device in test. Unfortunately I put the shunt in the 24V path, not on ground path...

I was working fine with only the AD2 connected to the shunt and evaluating the results. The AD2 was with the BNC board and I´ve attached the Ground to one of the legs of the shunt (near 24 volts). 

In a determined moment I decided to update the firmware to eval-uate a new behavior and connected the programmer to the device!  So I attached the programmer to the device! Everything stopped for a moment.

Apparently, the programmer when was connected short circuited the AD2 ground, which was the USB ground already attached to the ~24V power supply, with the ground of power supply. Apparently some loop was closed by the USB hub.

The USB hub is dead, and the AD2 has some problems connecting to others USBs, I´ve not been able to make it run, and the led does not turn on.

I´ve assumed that the the USB chip on AD2 is dead, and maybe some other chips on the board.

There is any procedure that I can do, or hardware troubleshoot so I can try to recover the device? Debug if the power supplies are working? Full schematics or so on?

My goal is to fix this! I want to evaluate if there is any component sensitive to reverse voltage that has any chance to be damaged too.

I´ve got another AD2 here (damaged) in our company, so this would be of a big help to know how to debug and try to solve this.

 

Hope there is some way!

 

 

[attila]

Hi @Igor Luiz

Sorry to hear this.

In case the device is not detected by the system verify the ferrites under the USB connector:

In case you get error during software connection (AVCC/PLL) verify the IC20:

 

[Igor Luiz]

Thanks @attila!

I´ve reviewed the 2 boards that I have.

There are some problems with the  a problem USB power control block.

I got some ADM1177 burned, problem with the 0.1 Ohm measure resistor, and problem with the dual FET. In resume, all this portion is not working properly. The digital power supplies seems to be fine after powering my board with external supply.

The AVVD5 was not working, I cannot scope properly to know if it is working or not, but the AVVD5 ia at 0V, so I image that the IC20 is damaged. I bypassed the IC20 in one board, and the supplies were working, but the FTDI chip does not connect, I think it´s dead.

On the other board I replaces some components, hoping that it works! The FTDI connects (this board had the FTDI chip replaced already), and have some errors of ERC. After this I measured the voltage between the 0.1 Ohm resistor, and the circuit seems to be consuming 300 mA, I thought that this consumption was high, but, there is a lot of things not working properly on the USB power block too, so it could be a lot of things.

I´m planning to buy some components to replace and see if it works, but I would like to make some further tests if there is really a way to fix this, because, if not, I will not buy these components.

Some questions:

1) There is any other test that I can do, bypassing the part of this power block, or It will give some errors (caused by the I2C ADM1177 not answering, or damaged)?

2) The FPGA need whats supplies to work properly and load the code? The digital Ones? Or the AVVD too? i would like to diagnose quick if the FPGA is working or not, because, in this case I will give up if I need to replace this.

3) Whats is the expected consumption if everything is working fine?

3) Some signals of enable like EN_AVCC are outputs from FPGA or from the FDTI module?

 

Thanks!

[attila]

Hi @Igor Luiz

I was hoping to have only the ferrites (FB18,19 under USB connector) or the power switch (IC20) damaged, which are easy to fix.
Having further issues, I don't think it worth continuing the troubleshooting, the repair might cost more than the device...

When the device is running in idle (FGPA programmed, oscillators, ADs, DAs) should consume about 1.4W (300mA)
Exactly what error message do you get? In case the LED starts to blink the FPGA got programmed.

 

[Igor Luiz]

Hi @attila!

Yes! I forgot to mention the ferrites! At first I replaced them!

Good news, based on your information about the consumption I imagined if one of the board could be fine, and only have problems with the MOSFET on the USB power block.

In my measured the values were not valid, so I bypassed it,  and the supplies were fine in the correct range now!

I plugged to the PC, and the device worked, I´ve tested the generator and scope, and everything seems to be fine!

I will buy the components of the USB power block and perform the parts replacement.

It´s interesting to note that this board that worked had the FTDI chip changed some time ago.

The other one I will need to do further tests, because I think the FTDI is not working. I will try in future to fix the second one too!

 

Hope I have good news soon!

 

 

 

 

[attila]

Hi @Igor Luiz

Good to hear that you have fixed one of the device. You have a working device to compare with the other one.
The FTDI is 'directly' supplied from USB 5V and the builtin 3.3V/1.8V regulator is used.
Let us know if you need any help.