LAUNCHXL-F28379D: Wrong VREFHIA - VREFHIB

Hi Luca,

Luca Polverini said:

For example the voltages of U19 mesured in R11 (VREFHIA)

You are measuring on the side of the resistor that VREFHI signal is on, just to be certain?

Luca Polverini said:

I do not understand if this is an hardware issue or a software issue. The second case it is likely because all of this happened after a pc change.

I do not think this could be a software issue, VREFHI input circuit is external HW. What do you mean by a 'pc change'?

Have you done some prior testing / evaluation with these boards? Were the boards VREFHI circuits previously working properly? i.e. ADCs sampling correct values.

Best,

Kevin

Hi Kevin,

- I've misured the voltages on both side of the resistor and they are pretty the same because the capacitor should look like an open circuit in cc. I've unplugged all the cables but the power from the boards.

- I've used them in the past and they worked properly. Few days ago I changed the notebook to program them. I am not sure that the launch configuration was good and both CPU1 and CPU2 received the program. I need only one CPU for now. So I've reset the board and I've re-loaded the firmware from the old pc. After this operation the ADC started working badly. After many attempts I started debugging the hardware and the measurements of VREFHI were compatible with the observed issues (low values).

I don't understand what happened to the boards and I am planning to replace the OPA, but before I would be sure that there isn't something SW happening or something that might have damaged the DSP pins.

Luca  

Hi Luca,

It seems like an odd issue. Did you run different firmware on the board between the two PCs, or always the same firmware?

Do you have a current limiting power supply to test with, to make sure the board isn't drawing too much current on the 5V and/or 3.3V rails. May be a quick tell if something is damaged.

Are you able to connect to the board and erase the flash? Just to make sure nothing is running on the device currently. It's difficult to say for certain what's happening right now.

Best,

Kevin

Hi,

I've removed the OPA350ea/250 and I've supplied an external VREF (3.0V).

The launchxl is powered through the header J10 and JP6 is on to supply the 5V rail; consumpiotn on the 3.3V power supply is 134 mA.

Now, VREFHIA and VREFHIB are stable around 3.0V and the current consumption on the VREF is about 1 mA.

I think that the OPs where damanged. I do not know the cause. 

Hi Luca,

Luca Polverini said:

I think that the OPs where damanged. I do not know the cause. 

Yes, that appears to be the case then. I'm not sure either. Do you have capabilities to replace the part on the board?

Best,

Kevin

Hello Kevin Allen18,

thank you very much for replying me.

At this point, I would like to replace them with "stronger" components. May you suggest OPAs capable of withstand higher voltages/ESD/etc... given the same package?

Best regards,

Luca

Hi Luca,

I'd suggest asking this same question on the amplifier forum. They could give better pin-to-pin suggestions than me.

https://e2e.ti.com/support/amplifiers-group/amplifiers/f/amplifiers-forum

Best,

Kevin