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.

MSP430FR6047: External Amplification and External / Internal DC-Bias Conflict

Part Number: MSP430FR6047
Other Parts Discussed in Thread: TIDA-01486, THS3095

I have recently designed a "UltraSonic Flow Meter" based around the MSP430FR6047 that uses external switches and amplification circuitry, almost identical to the TIDA-01486 TI Ultrasonic Flow Transmitter Reference Design. The external switch and amplification circuitry allows for 4 Ultrasonic Flow Sensors (US0014-001) to be connected and driven at their maximum voltage (5Vpp).

An ADC Capture reveals the following:

I believe the contention between the external DC-Bias that I'm applying to the Non-Inverting Input of the Rx OpAmps (THS3095) and the Rx-Bias applied by the MSP430 during signal acquisition is the reason the signals are not centered around 0 Amplitude. An over-voltage of the ADC input may also be occurring but I believe this can be handled by decreasing the gain of the external Rx OpAmps and/or Internal PGA.

The issue our software engineer has encountered while attempting to disable the internal Rx Bias applied by the MCU is detailed below.

We are running a modified version of the 'MSP430FR6047EVM_USS_Water_Demo' example program.

We've modified the SAPH initialization function, USS_updateSAPHConfiguration() in USSSWLibConfiguration.c in an effort to remove the DC bias.

From the User Guide:
However, after making the software changes above a 400mV DC-Bias is still observed on the ADC Input.
Our goal is to disable the Internal Rx-Bias, but not the Internal Tx-bias, to allow for external Rx biasing.
What exact modifications to the MSP430FR6047EVM_USS_Water_Demo are required to disable the Internal Rx-Bias while maintaining the rest of it's functionality?
Please let me know if any additional information is required or if you have any insight on our project.
Thank you,
Trenton Miller

**Attention** This is a public forum