Other Parts Discussed in Thread: EVM430-FR6047, MSP430FR6047
We are working with Ultrasonic Transducers along with TI's USS. We have out own custom PCB based on EVM430-FR6047 schematics. We are facing issue in the signal output when no transducer is connected (CH0 and CH1 are kept open, except the RC circuitry as given below)
The signal with gain of 22.8db (No transducer is connected, is given below). As can be seen the signal strength goes above 400. This messes up with our algorithm to process the data.
When the MSP430FR6047 is replaced with a newer one. We see that USS shows reduced signal strength (at same gain 22.8db and no transducer connected).
This behavior is seen in multiple PCBs. Currently, we are of the view that MSP is introducing some noise just prior to PGA. To verify this, we also checked that a Good PCB and Bad PCB (which gives high signals without any transducer) signals at the CH0IN and CH1IN pins. We are getting similar voltage waveforms as shown below (Blue curve is the CH0IN and similar is obtained on CH1IN for both PCBs). In out opinion, this means that the DC is introduced and amplified inside the MSP, somewhere. Can this be a case? If yes, How to resolve this as we are seeing this issue in multiple PCBs?
We need urgent help to resolve this.