ADS1262EVM-PDK: out-of-the box EVM, getting positive rail faults on shorted input

Hi Patrick,

Can you repost these images that you are referring to? We cannot access google drive folders due to the company's internal firewall. Perhaps you can place them in a Word doc or a PDF and attach that?

When you perform a shorted input test, please ensure that the applied voltage to both pins is at mid-supply ([AVDD - AVSS] / 2). This is generally how the test is performed that yields the noise values you see in the datasheet

Also, please be aware that any of the PGA rail flags should be ignored when the PGA is bypassed. The EVM GUI might show errors, but these are only relevant when the PGA is enabled.

-Bryan

Thanks Bryan.  I've attached the Word files.  I'm at 0V shorted, midway between +2.5 and -2.5.   More problems however.  I thought my wall power supply might be dropping below 5V, so I plugged the MMBO into a 12VDC/3A wall supply.   I think I've smoked it -- no LEDs, no numeric output, ADC/Pro can's see it.  The label on the board says it wants 6V/500A, but your EVM user manual specs 5.5 to 15V min 500 mA (2.3.1.1 p8), and the revision history suggests that a change in wall power was made between the original EVM and Rev A in 2015 (p31).  My MMBO is labeled 6462011 Rev E  6462012 PWB D near the USB connector if that helps.  Could you please authorize a warranty replacement?  Still interested in your answers.Just got my evm.docx

Not sure the files went.  Resending.5241.Just got my evm.docx

Hi Patrick,

From the ADCPro images you sent, it looks like the resulting voltage you are getting in the ADS1262 output is close to the offset voltage of the device (350uV typical). Can you try running an offset calibration first and see if the results improve? This is discussed in section 9.4.9 in the ADS1262 datasheet.

Can you also post an image of the connections to the MMB0 board? You mention both a wall supply and +/-2.5V operation, which require different supplies to operate (the +/-2.5V supplies are generated from the +/-5V supplies connected to J14 - these supplies power the MMB0, not the wall supply). This is discussed in the first paragraph of section 2.3 as well as in subsection 2.3.2 in the ADS1262 EVM user's guide.

-Bryan

Can't run calibration as my unit is deed as described in my last post.  I've attached the photo you requested.  I've checked all jumpers and switches and they are in the default configurations -- I haven't touched them.  

i have not attached a bench external supply.  I was trying  to run from the internal supply as described  in 2.3.1,2.3.1.1, and 2.3.1.1.1.  The language is confusing.  2.3 and 2.3.1 both refer to a "single 5V supply". Section 2.3.1.1 specifies a 5.5-15V wall supply..  Which is it?  I tried 12V and smoked the EVM  How do i get my EVM replaced?

Hi Patrick,

In my first reply to you I mentioned shorting the inputs to mid-supply, and in your response you said "I'm at 0V shorted, midway between +2.5 and -2.5". I assumed this meant you were using bipolar supplies at +/-2.5V. Now you are saying that is not the case, so can you please explain what you meant by this comment? Ideally if you are using a 5V supply you should be shorting both inputs to 2.5V.

Also, what is the position of S2? The image you included is blurry, but it looks like it is set closer to the marking "4C", when it fact it should be moved to the other position for a unipolar 5V supply. Setting S2 to the "4C" sides sets the device to use a bipolar supply.

I will look into your question about the EVM replacement. Have you checked the various test points across the board to see what, if anything, is still functioning?

-Bryan

Bryan -- thanks.  I'd like to separate the two issues -- replacement under warranty and what I'm trying to do.

Hi Patrick,

1. I will address this question with you offline. But in general, the MMB0 can handle a 12V input as you described it, via the wall supply. The output from the wall supply is sent to TI's REG104, an LDO that can support a VIN of up to 15V. The REF104 output voltage in this case is 5V. You can review the MMB0 schematic here: https://e2e.ti.com/support/data-converters/f/73/p/775258/2868385#2868385
2. In order to use a bipolar supply, you would need to connect external supplies +/-5V supplies to the MMB0 board via J14, as described on page 10 of the user's guide. In this case, you would not use the wall supply. However, you had mentioned that you only connected the 12V wall supply, not any additional external supplies, so then the supply to the ADC (AVDD) is 5V unipolar. Assuming all of the switches / jumpers / etc. are in their default positions, the EVM should have worked as expected at this point. Also note that the internal VREF is 2.5V, so if you wanted to use a higher VREF voltage e.g. 5V, you would need to select external VREF in the ADCPro menu as well as the appropriate REFP/REFN input pair.

-Bryan

1.  I don't know what went wrong, but i plugged in a 12V 3A wall adaptor and the MMBO smoked.  It was working earlier with a 5V supply.  I changed no jumpers, and did nothing else.  I'd like to return it under warranty.

2.  I didn't send the FSR reference screen shot (and can't now) but it showed -2.5 to 2.5.  

Sorry, I should have said FSR Scope not reference.