This thread has been locked.
If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.
Part Number: ADS1191
I am trying to use the ADS1191 in a signal chain the has a load-cell bridge and INA333. I am trying to calculate the required CM of the device and am confused by the equation and example in the ADS1191 datasheet:
If I take AVDD =3V, gain =6, Vmax_diff = 350mV, and AVSS = 0V.
3V - 0.4V - 1.05V > CM >0V + 0.4V + 1.05V
1.55V > CM > 1.45V
In the ADS1298 datasheet the value of 0.4V is changed to 0.2V and the example and equation work out. I wanted to check if ADS1298 is correct or if the equation in the ADS1191 is correct but has the wrong answer in the example.
I am trying to understand how I need to set the CM input of the ADS1191 with respect to setting the CM output of the INA333.
I will be using AVDD =5V and a gain of 12.
The max-diff voltage will be 336mV calculated from equation 4 in the ADS1191 datasheet. Given internal 4.033Vref and Gain =12
Max(INP-INN) < (Vref/Gain) ---> Max(INP-INN) < 4.033V/12V ----> Max(INP-INN) = Vmax_Diff = 336mV
Taking that number and plugging into the CM equation found in ADS1298 datasheet:
If I take AVDD =5V, gain =12, Vmax_diff = 336mV, and AVSS = 0V.
3V - 0.2V - 1.05V > CM >0V + 0.2V + 1.05V
2.784V > CM > 2.216V
This means I can set my CM for a single ended implementation at mid supply (2.5V) and have a signal swing of 336mV about the CM and satisfy the requirements.
Is this understanding correct?
In reply to Matt Mendez:
Thanks. Looking forward to finding out the correct answer.
Then I can stop scratching my head over why I couldn't make the simple equation work out.
In reply to Dakotah:
All content and materials on this site are provided "as is". TI and its respective suppliers and providers of content make no representations about the suitability of these materials for any purpose and disclaim all warranties and conditions with regard to these materials, including but not limited to all implied warranties and conditions of merchantability, fitness for a particular purpose, title and non-infringement of any third party intellectual property right. TI and its respective suppliers and providers of content make no representations about the suitability of these materials for any purpose and disclaim all warranties and conditions with respect to these materials. No license, either express or implied, by estoppel or otherwise, is granted by TI. Use of the information on this site may require a license from a third party, or a license from TI.
TI is a global semiconductor design and manufacturing company. Innovate with 100,000+ analog ICs andembedded processors, along with software, tools and the industry’s largest sales/support staff.