CC2541: Is the Vref value of CC2541 differnt from the datasheet value?

Ca Suu

Prodigy 30 points

Part Number: CC2541
Other Parts Discussed in Thread: CC-DEBUGGER

Tool/software:

I 'm using the CC2541 with using the internal voltage for Vref.

I am inputting the output from the AD8497(ANALOG DEVICES) into the AD converter on the CC2541.

A type K thermocouple is connected to the AD8497.

When I connect the CC-DEBUGGER to the CC2541 and check the results, the measurement point is 200°C, but the output temperature is 207°C.

When I use an external voltage of 1.24V instead of the internal voltage for Vref, I can correctly measure 200°C.

The internal voltage for Vref should be specified as 1.24V in the product specifications, but it seems to be operating at 1.21V.

Why is this happening?

4 months ago

0 Alex Fager 4 months ago

TI__Genius 13504 points

Hello Ca Suu,

I hope you are doing well. The internal reference voltage should be 1.24 V as you noted, however it seems like in an older revision of the datasheet it was 1.15 V (revision B August 2012); here I would recommend sticking with what the datasheet currently recommends which is 1.24 V for the internal reference voltage.

Thanks,
Alex F

0 Ca Suu 4 months ago in reply to Alex Fager

Prodigy 30 points

Hi Alex,

Thank you for your helpful explanation.

It seems that the internal reference voltage of CC2541 is outputting 1.21 V.
Has the internal reference voltage ever been specified as 1.21V in the past?

Does the internal reference voltage value vary from chip to chip in the CC2541?
When using the CC2541, should I calibrate and correct the output value?

Best regards,
Ca Suu

0 Alex Fager 4 months ago in reply to Ca Suu

TI__Genius 13504 points

Hello Ca Suu,

I have looped in our HW expert to see if they can help answer your questions here.

Thanks,
Alex F

0 Ca Suu 4 months ago in reply to Alex Fager

Prodigy 30 points

Hi Alex,

thank you for your reply.

I’ll wait for the answer.

Thanks,

Ca Suu

----- Additional Information -----

Following characters are written on the surface of the CC2541 I am using.

CC2541Q1

F256

TI2CI

COT6 G4

0 Andrew Lugo 4 months ago in reply to Ca Suu

TI__Intellectual 2600 points

Ca Suu,

1.24V is the typical Vref value and there will be part to part variation. You will need to calibrate the device to account for this variation or use an accurate external supply for your reference voltage. I hope this helps.

Regards,

Andrew

0 Ca Suu 3 months ago in reply to Andrew Lugo

Prodigy 30 points

Hi Andrew,
Thanks for your explanation about the Vref variation.
Your advice on calibration and using an external reference really helps.
I appreciate your support!

Best regards,
Ca

0 Andrew Lugo 3 months ago in reply to Ca Suu

TI__Intellectual 2600 points

Ca,

No problem. You're welcome.

Regards,

Andrew

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CC2541: Is the Vref value of CC2541 differnt from the datasheet value?