ADS1299 "Nbit" resolution

Meagan Lloyd

Hello,

I am interested in finding how many 1299's I can daisy chain and am using equations 6 and 7.

Can you please clarify how Nbits (device resolution) should change with respect to the data rate? How can I find the device resolution for say 16kSPS. Isn't the resolution set to 24 bits by the ADCs? If a lower resolution is needed to accommodate timing constraints, how does the chip scale back it's resolution?

Thank you,

Meagan

over 10 years ago

0 Brian Pisani over 10 years ago

TI__Mastermind 38745 points

Hey Meagan,

The device does not scale the number of bits it outputs based on the data rate. I'm not sure why the datasheet includes that parenthetical. You may have discovered either a typo or a rather confused writing style.

Regards,
Brian Pisani

0 Meagan Lloyd over 10 years ago in reply to Brian Pisani

Prodigy 100 points

Hi Brian,

Sorry to bother you again. Regarding equation 7. Do you think there should be an extra parenthesis in the denominator? I'm wondering if the units make sense, since the clock cycle * total bits makes sense. And "+24" is due to the status bits? i.e. fsclk/(fdr(Nbits*Nch + 24))? If not, could you please explain why?

Thank you and sorry for the inconvenience,

Meagan

0 Ryan Andrews over 10 years ago in reply to Meagan Lloyd

TI__Guru 66206 points

Hi Meagan,

Yes, the total number of bits should include (n-bits x #channels) + STATUS. We will make a note to add the missing parentheses to this equation in the next datasheet revision.

Best Regards,

0 Meagan Lloyd over 10 years ago in reply to Ryan Andrews

Prodigy 100 points

Thank you!

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ADS1299 "Nbit" resolution