ADS1298: ads1298

Hi Ali,

Thanks for reaching out with an update on your project! We communicated offline earlier this year via your myTI email address. That email no longer seems to be active.

If you are using the same DC supply for AVDD and DVDD, I would recommend a ferrite in between them with adequate bypass capacitors on either side. The digital supply will see more dynamic current loads, producing voltage transients which can couple into the analog signal path and add noise to the measurement. Otherwise, if the two supplies are generated separately, you can avoid using ferrites.

Regards,

Ryan

Hi Ali - I had recommended to follow your 3V DC/DC converter with an additional LDO to reduce the AVDD supply to 2.5V. Otherwise, the AVDD-AVSS delta exceeds the Recommended Operating Conditions of the ADS1298.

Are you using 3V as your I/O voltage levels? If you need 3V I/O, then I would boost the DC/DC output further, and follow with two separate LDOs: one for 2.5V AVDD and another for 3V DVDD. Else, you could follow AVDD with another LDO and lower your I/O supply even further to, say, 1.8V.

Regards,

Ryan

Yes, I'm referring to the logic levels. For example, the MCU's input levels are as follows:

• Logic high: 0.75*3.3V = 2.475V (min)
• Logic low: 0.25*3.3V = 825mV (max)

Comparing the logic output levels from the ADS1299's datasheet:

• Logic high: 0.9*2.5V = 2.25V (min)
• Logic low: 0.1*2.5V = 250mV (max)

The ADS1299 high-level output voltage is not guaranteed to be above the minimum requirement for your MCU high-level input voltage. It would be best to connect the ADS1299 DVDD to the same VDD supply used by the MCU to ensure data is transmitted correctly.

Regards,

Ryan

Hi Ali - Can you please send it to me via email? I will review it offline and share feedback next week.

Regards,

Ryan