CC2640R2F: ADC INL compensation

trackert

Part Number: CC2640R2F

Hi,

Looking at the datasheet for this part (SWRS204A, Figure 5-22) there is significant ADC code-dependent INL; for example the mid-rail would seem to have 2044 and 2048 as adjacent codes. What I am wondering is whether this is accounted for in the TI library functions for ADC conversions (AUXADCValueToMicrovolts, etc)?

If not it would seem that this could be done in a separate routine by selectively adding bits to the codes between ~1400 and 2048 to bring the INL back to ±1 LSB. Does this make sense to do or is there something I am missing?

Regards,
Jamie

over 5 years ago

0 PM over 5 years ago

TI__Mastermind 27145 points

Hi,

We will look into it and get back to you ASAP. Please bear with us.

Thanks,

0 trackert over 5 years ago in reply to PM

Intellectual 370 points

PM said:

Hi,

We will look into it and get back to you ASAP. Please bear with us.

Thanks,

PM

Hi,

Any update on this?

Jamie

0 FI over 5 years ago in reply to trackert

TI__Mastermind 21190 points

Hi,

I have forwarded this to the driver team to look into. They will get back as soon as possible.

Regards,

0 FI over 5 years ago in reply to FI

TI__Mastermind 21190 points

Hi,

Due to holidays the response was delayed. I will check with the driver team this week and get back.

Thanks for your patience.

0 FI over 5 years ago

TI__Mastermind 21190 points

Hi,

It doesn't seem like AUXADCValueToMicrovolts accounts for the corrections. I think you should use AUXADCGetAdjustmentGain and AUXADCGetAdjustmentOffset in conjunction. Offset and Gain values are stored in the FCFG1 area during manufacturing.

regards,

0 trackert over 5 years ago in reply to FI

Intellectual 370 points

Hi,

I was aware of these routines and was already using them but this doesn't address the INL question. Currently I do the following to obtain a millivolt value:

On startup get the factory gain and offset values
Read the ADC
AUXADCAdjustValueForGainAndOffset() using the obtained factory values
AUXADCValueToMicrovolts() to convert to the corresponding microvolt value

It would seem straightforward to fix the large INL steps described in the datasheet by simple bit manipulation of the ADC code. I am not sure if this is already being done in the library routines, however, hence my question. So, do any of the library routines accomplish this - AUXADCAdjustValueForGainAndOffset() would seem like the most likely candidate?

Best Regards,

Jamie

0 trackert over 5 years ago in reply to trackert

Intellectual 370 points

... actually I just found the code in the driver library documentation - I thought these functions were obscured:

// Apply gain and offset adjustment
adcValue = (((adcValue + offset) * gain) + 16384) / 32768;

so there is no compensation for INL errors. Looks like a good candidate for a roll-your-own conversion function.

Regards,

Jamie

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CC2640R2F: ADC INL compensation