ADS1299: ECG amplifiers capable of measuring smaller biopotential signals

Saba Eas

Part Number: ADS1299
Other Parts Discussed in Thread: ADS1296, , ADS1198, ADS1298

Hi,

I need a suggestions on choosing a low power amplifier that is capable of measuring very small bio potential signals such as fECG. I saw that ADS1296 has a video (https://www.digikey.com.au/products/en?keywords=A02SUR02SUR32W152B) suggesting it's capable of that. Then I came across ADS1299 which has very low input referred noise.

Is there any other options I am missing? Also I am wondering why ADS1299 is not categorized as a low power amplifiers whereas ADS1296 has low power capability mentioned in it's description.

Thanks & Regards,

Saba

over 4 years ago

0 Alexander Smith over 4 years ago

TI__Mastermind 47595 points

Hi Saba,

We typically recommend customers to not use an amplifier before the ADS1299. Since the input referred noise of the ADS1299 is so low, adding an opamp in front of it with a gain stage would likely increase the noise in the measurement, resulting in a decrease of the overall SNR. Instead of using an amplifier before the ADS1299, I suggest that you consider reducing the reference voltage of the ADS1299 so that your signal uses a greater portion of the full-scale input range.

The ADS1299 draws about twice the amount of power per channel compared to the ADS1296. This can be seen in the overview post of the BIOFAQ: https://e2e.ti.com/support/data-converters/f/73/p/772058/2855202

0 Saba Eas over 4 years ago in reply to Alexander Smith

Intellectual 290 points

Hi Alex,

Thank you for the response.

The comparison chart was very helpful.

Regarding the electrode connection for ADS1299EEG-FE PDK, In the kit we already have for ADS1198, there is a DB15 connector installed and we found it very convenient for our testing purposes.

What would you suggest as a best method to connect the channel inputs to the subject?

Kind Regards,

Saba

0 Alexander Smith over 4 years ago in reply to Saba Eas

TI__Mastermind 47595 points

Hi Saba,

I recommend using a wet electrode. I do not have any specific recommendations as TI does not manufacture electrodes.

0 Saba Eas over 4 years ago in reply to Alexander Smith

Intellectual 290 points

Hi Alex,

Thank you for your response.

We are using wet electrodes. But because of the lack of DB-15 connector in this PDK model, we are using coax cables with one end connected to AGND of the board. Do you think that is sufficient in the connections point of view? Or do you recommend any connecting cables that we can use with this PDK.

Kind Regards,

Saba

0 Alexander Smith over 4 years ago in reply to Saba Eas

TI__Mastermind 47595 points

Hi Saba,

That should be fine.

0 Saba Eas over 4 years ago in reply to Alexander Smith

Intellectual 290 points

Hi Alex,

Thank you for the confirmation.

As per the earlier response from you for this thread. I found the comparison for the amplifier specs. But when comparing with the data sheets of the individual ADC's there seems to be a mismatch or a misinterpretation from me. Please compare the data sheets of ADS1198 and ADS1298. In their datasheets it seems ADS1198 consumes 0.55 mW/Ch whereas ADS1298 consumes 0.75 mW/Ch but the below attachment it seems different. Please help me solve this confusion.

Regards,

Saba

0 Alexander Smith over 4 years ago in reply to Saba Eas

TI__Mastermind 47595 points

Hi Saba,

Will you please share how you came up with these values?

Make sure you're looking at the values for AVDD = 5V.

0 Saba Eas over 4 years ago in reply to Alexander Smith

Intellectual 290 points

Hi Alex,

Sure. The table of summary from here. And the power consumption for ADS1298 & ADS1198 are on the front page of their respective data manuals under features section.

Regards,

Saba

0 Alexander Smith over 4 years ago in reply to Saba Eas

TI__Mastermind 47595 points

Hi Saba,

The 0.75mW/ch as shown on the front page of the ADS1298 DS is for AVDD = 3V and low power mode.

The 2.19mW/ch as shown in the table is calculated from using AVDD = 5V and high resolution mode.

Please see the "POWER SUPPLY (RLD, WCT, AND PACE AMPLIFIERS TURNED OFF)" table for details.

0 Saba Eas over 4 years ago in reply to Alexander Smith

Intellectual 290 points

Hi Alex,

Thank you for clearing it out.

I was on holidays and apologies for the late response.

what is the difference between high resolution mode and low power mode? When we switch between these modes, any jumper settings needs to be done other than the register settings?

Kind Regards,

Saba

0 Alexander Smith over 4 years ago in reply to Saba Eas

TI__Mastermind 47595 points

Hi Saba,

The difference is in the name of the modes. One is high resolution (higher accuracy) and the other is low power. See the datasheet for more detail.

Nothing should need to be changed on jumpers.

0 Saba Eas over 4 years ago in reply to Alexander Smith

Intellectual 290 points

Hi Alex,

Thank you for the response.

Kind Regards,

Saba

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ADS1299: ECG amplifiers capable of measuring smaller biopotential signals