1. Refine the Rfilt and Cfilt Values TIPL 4404 TI Precision Labs – ADCs
Hello, and welcome to the TI Precision Lab discussing input offset voltage, VOS, and input bias current, IB. In this video we’ll discuss
Created by Art Kay

2. Refine the Rfilt and Cfilt Values
Use the OPA625 model form TI.com, and the ADS7056 model developed in the previous quiz to find the optimal value for the RC charge bucket circuit. Also use the calculator results below.

3. Solutions

4. Refine the Rfilt and Cfilt Values
Set the error voltage source.

5. Refine the Rfilt and Cfilt Values
Use the OPA625 model form TI.com, and the ADS7056 model developed in the previous quiz to find the optimal value for the RC charge bucket circuit.
Click here for the TINA file

6. Refine the Rfilt and Cfilt Values
Simulation results zoomed in on error bands of ±100mV

7. Refine the Rfilt and Cfilt Values
Simulation results zoomed in on error bands of ±50mV, 800ns to 900ns. Error curves 1, 2, and 3 are best.
Click here for the TINA file

8. Refine the Rfilt and Cfilt Values
Simulation results zoomed in on error bands of ±50mV, 800ns to 900ns. Re-do parameter stepping with 5.6 to ohms. Note that many R values give small final error. Choose one with no overshoot and good error (e.g. Error(4) = -105nV, ohms or standard value = 8.56 ohms).

9. Refine the Rfilt and Cfilt Values
Re run with fixed standard resistors = 8.56 ohms. Final Error = -106nV, Target = 152uV. Very good settling (far better than the error target).
Click here for the TINA file