Other Parts Discussed in Thread: LMP91200, MSP430I2040
I would like to use a MSP430i-series MCU (MSP430I2040) to interface to the LMP91200 pH Sensor AFE. The 430i 24-bit SD converter will interface to the differential output of the AFE and the parallel IO of the MCU will drive the AFE digital control signals.
Looking at the data sheet specifications of the 430i 24-bit SD converter raises some questions. Referring tp table 5-22: Gain Error (EG) of +/- 2%, and Offset Error (EOS) of 4mV at a gain of 1. At the gain of 1 input range of +/- 928 mV these specifications yield a measurement accuracy consistent with an 8- or 10-bit ADC.
Is there a calibration procedure that can be performed in firmware to significantly inprove the SD converter accuracy? And if not, what application is there for an ADC with 24-bit resolution but such low accuracy?
My bottom line design requirements are +/- 0.2% accuracy over the input range of 0 - 850 mV at nominal temperature. I can use an external voltage reference with 0.1% accuracy. That leaves an error budget of 0.1% for the SD converter.
Any guidance will be appreciated. Other than that, the 430i MCU line is perfect for this application.
Regards, Steven
