Programmable Devices
CPLDs, FPGAs, SoC FPGAs, Configuration, and Transceivers
20638 Discussions

Was my chip burnt ?

Altera_Forum
Honored Contributor II
1,236 Views

I tested the voltage of ASM1117 1.2V on my board, which is 2.5V, and the current is 190.2mA. Obviously, the VCCINT of cyclone2 should be 1.2v, so i doubt whether the chip was burnt.  

When i cut the supply of voltage with cyclone2 chip, the voltage of ASM1117 1.2V is 1.254V, the ASM1117 3.3V chip works well whether the power is cut or not, it is 3.33V all the same. 

Is cyclone2 burnt ? Anyone who can tell me please. Thanks very much.
0 Kudos
9 Replies
Altera_Forum
Honored Contributor II
386 Views

The Absolute maximum rating on that is 1.8 V, so since it was stressed, that answer is probably yes. 

 

Usually it will fail as a short to ground, however, since you were only pulling 190 mA, you have some chance that the chip survived. 

 

Have you identified what caused the supply to go to 2.5 V? Was it an issue with the feedback circuit or does it only happen when loaded.  

 

Since you were able to pull isolate the 1.2 supply, try looking on the other side with the supply up, and see if you a short to a 2.5 V supply. 

 

If you a have another board that wasn't powered up, that exhibits the same problem, it's probably a short in on the board. 

 

Pete
0 Kudos
Altera_Forum
Honored Contributor II
386 Views

Hello,anakha. Thanks for you advise. 

I tested my board and found that the voltage of the pins are all right. In my first post, the  

voltage of ASM1117-1.2V I tested was 2.5V , the reason is that I forget to jump the GND line to the other board, the two boards shared different GND ,so the voltage was 2.5V. When I lined the two board GND together, the voltage turned to normal. 

Unfor, new problem appears. There is no short on my board before power on, and nothing wrong with the ASM1117-1.2V chip, but once power on, the ASM1117-1.2V chip becomes hot. Then I cut Power Supply, test the board, and find the FPGA 1.2V pins are connected to GND. However, after about 3 minutes, I test the board again,the short is gone. 

I repeat the experiment , the short repeats. 

So, my FPGA was burnt, wasn't?
0 Kudos
Altera_Forum
Honored Contributor II
386 Views

That's the first time I've heard of an FPGA failure shorting then after time recovering (like a thermal fuse). Every failure I've ever seen once shorted, stayed shorted to ground. 

 

Have you tried using JTAG to check to see if the FPGA responds? 

 

Are you programming the FPGA at all? 

 

One possible source of this issue, if you have a bitfile loaded in the flash device, some versions of quartus defaulted to all unused IO as output driving ground. this could potentially explain the short then recover. But only if you have some IO's connected to the 1.2 rail. (Possible, if your board pinout is compatible with all the package compatible devices. Usually the largest device has more VCC_INT than the smaller devices) 

 

It's a long shot, but work looking into. 

 

Pete
0 Kudos
Altera_Forum
Honored Contributor II
386 Views

How do you measure the short? Do you use a digital multimeter with the classical "beep" function? Take care that the impedance to ground of a 1.2V Vcc track coming from the ASM chip is typically at a limit (around 90ohm) that makes a "beep" or not. So you may better try to measure the resistance value and check that it is always the same at every power up. 

Anyway I suggest you to replace the ASM chip, it may be damaged and create problems to the FPGA.
0 Kudos
Altera_Forum
Honored Contributor II
386 Views

Thank you very much,OrchestraDirector .  

I changed the FPGA chip and the ASM1.2V chip on the board. The program now can be downloaded to the FPGA, JTAG and AS mode are successful , but the config_done pin is not pulled to high(the voltage i tested is 1 mv). I don't know what' going on and what happened ? 

There also exists another problem on my board , I have 3 LEDs linked to four I/O pins of FPGA( one point to one), the other side of the LEDs is connected to K resistance pulled to 3.3V. When power on , the LEDs should be off. First i just welded only one led to the FPGA pin, when power on ,the led was on. So i welded the second led , strangely the first become dark than before, and the second led was on and brighter than the first one. After than i welded the third one , when power on ,the third one is normal, the fist two ones is the same as before and still bright. 

I tested the impedance to ground of the 3 pins of FPGA, the first one which the led is dark is 1.5K, the second one which is bright is 350ohm, the third which is normal is 110K. I can't explain the reason. Why? 

In my fist post I said the shorting then after time recovering of the FPGA 1.2Vpins to GND, the reason I think is associated with the capacitance characters, I will go on checking the circuit. 

Now the AMS 1.2V chip is a bit warm but not hot , the FPGA is also warm when power on.
0 Kudos
Altera_Forum
Honored Contributor II
386 Views

Did you use a cleaning solvent after your soldering re-work? 

The resistance values are really fuzzy, sometimes it happens if the soldering flux is mucking up the tracks.
0 Kudos
Altera_Forum
Honored Contributor II
386 Views

A quick check if the chip is ok or not is provided by the Auto-detect in the programmer options. If you are programming the board you can use this feature to ascertain if the chip is defective. 

 

regards, 

Kumar Vijay Mishra.
0 Kudos
Altera_Forum
Honored Contributor II
386 Views

 

--- Quote Start ---  

Did you use a cleaning solvent after your soldering re-work? 

The resistance values are really fuzzy, sometimes it happens if the soldering flux is mucking up the tracks. 

--- Quote End ---  

 

:p It is the problem! Now my board turned to normal, the AMS chip and FPGA are all properly. 

Still exists the CONF_DONE not being pulled to high.:confused:  

When power on , i measure the voltage of PIN3 ,4,7,8 and found PIN3 is 3.10V, PIN4 is 3.10V,PIN7 is 0.19V, and PIN8 is 1.02V, the chip is EP2C5T144c8n. The I/Opins voltage of bank2 is different too , some is 3.10V,and some is 1.01V.:confused:  

Shouldn't the voltage of I/Opins be 3.3V?
0 Kudos
Altera_Forum
Honored Contributor II
386 Views

OK, that's very good! 

About the strange behaviour at power up of the I/O pins I suggest you to follow the clues posted by Brad at: 

 

http://www.alteraforum.com/forum/showthread.php?t=3404&page=2 

 

About the strange behaviour of the CONF_DONE pin you may try to replace the pull-up resistor connected to that pin.
0 Kudos
Reply