OPA340 driving ADS7816 - 12bit ADC Errol Leon, Analog Applications Precision Linear Analog Applications October 5, 2016
Summary Assumptions of ADC 5V supply same as Vref Fclk runs at 3.2MHz Model is ½ LSB accurate Model and simulate 12 bit ADC from ADS7816 datasheet Model and simulate OPA340 directly driving 12 bit ADC ADS7816 Model and simulate OPA340 directly driving 12 bit ADC ADS7816 with Rflt and Cflt Summary and recommended circuit
Modeling ADS7816 - 12bit ADC
ADS7816 - ADC Modeling - Calculations
ADS7816 - ADC Modeling - Calculations
ADS7816- ADC Modeling- Schematic Equivalent circuit of ADC CSH - sample capacitor 25pF RSW – switch resistance 187Ω R1 – voltage source interface resistance 100Ω
ADS7816- ADC Modeling- Simulation
Modeling OPA340 directly driving ADS7816
OPA340 directly driving ADS7816- ADC Modeling- Schematic R2, R3, and R4 are used only for simulation convergence.
Transient Analysis of OPA340 directly driving ADS7816 circuit Settling Time Settling time within a ½ LSB of Verror at 11.61uV
Modeling OPA340 with RC Filter ADS7816
OPA340 with RC Filter to ADS7816- ADC Modeling- Schematic R2, R3, and R4 are used only for simulation convergence.
Transient Analysis of OPA340 directly driving ADS7816 circuit Settling Time Settling time within a ½ LSB of Verror at 438.1uV
Transient Analysis of DC Voltage Circuit Settling Time - Summary Both circuits are within a 1/2 LSB setting time. Recommended to use RC filter to mitigate 2nd and 3rd order effects based off of parasitic switching capacitance from the ADC as well as filtering high frequency noise..
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