Nexys4 DDR

[Leo_W]

Hi digilent，

My computer could not recognize N4. After detection, it found abnormal voltage of IC5 pin, but there was no schematic diagram of this part. I would like to try to repair myself, hoping to have this part of the schematic and chip signal.

 

Thanks!

[Bianca]

Hi @Leo_W

In this picture your board is turned off. Does it power when you switch it on? Does the power led go on? What do you mean by weird voltage on the VCC pin of IC? What did you measure there?

If the board does power on, can you tell me what shows up in device manager? If anything at all, even if unknown device, give me the Hardware ID..

Regards,

Bianca

[Leo_W]

On 11/20/2020 at 11:16 PM, Bianca said:

Hi @Leo_W

In this picture your board is turned off. Does it power when you switch it on? Does the power led go on? What do you mean by weird voltage on the VCC pin of IC? What did you measure there?

If the board does power on, can you tell me what shows up in device manager? If anything at all, even if unknown device, give me the Hardware ID..

Regards,

Bianca

Hi @Bianca

The pin on the IC5 chip was supposed to be 3.3v, but I got only 1v.The board can be powered on normally, but the display is an unknown device.So I think there is a problem with IC5, but I don't have the relevant schematic diagram or chip model.

 

[Bianca]

Hi @Leo_W,

So, I will try to explain to you something from that schematic.... I see that you opened a lot of topics, some of them answered by my colleagues. I suggest you keep all the questions related to a board, or to the same problem in the same topic, otherwise, we can't follow up with you. 

You asked about IC20... That is an LDO that makes the FT3V3 from the USB 5V0... all the FTDI environment is powered by that FT3V3. 

Like I said previously in a topic, the FTDI has an internal LDO that makes generates the voltage for the core. Initially I thought the FTDI was powered from 5V0 so it made a 3V3 but in this particular circuit, it's powered from FT3V3 and it makes the FT1V8. 

I'm telling all of this because:

- IC5 is an EEPROM. It is powered from FT3V3 and has pull-ups to FT3V3 and everything that comes from the FTDI is also 3V3.... I don't know on which pin you measured 1V but unless a component from the whole environment is burned internally, you wouldn't be able to see 1V... If IC20 would be burned you wouldn't see anything. 

-If you really see 1V instead of 3V3 it means that the FTDI is actually powered from 1V. The minimum requirements for the FTDI is 3V. I mentioned before that it has an internal LDO that makes 1V8 from 3V3 for the core.... it is physically impossible to make 1V8 from 1V0, therefore the FTDI shouldn't work at all. 

-The fact that you can see the board in device manager even if it's not correctly recognized, implies that the FTDI is working, therefore you have at least 3V on FT3V3. With just 1V, nothing should've shown up. 

I am still bugged by that 1V, which I don't know where you measured, since you said you don't know the chip part number, but for now we'll try to see if we can al least communicate and reprogram the EEPROM. If that works, you don't have an electrical problem, but a driver one. 

It'll send you a private message with some instructions.

Best regards,

Bianca