TDC1000: SNAA284A 差分激励方案，发送和接收电路PCB怎么布线才能让Delta-TOF at Zero Flow 更好？主要是接收换能器怎么接地。

Dear TI Support Team,

I am currently developing an ultrasonic gas meter measurement circuit based on MSP430FR6043, and the overall architecture is inspired by the SNAA284A differential excitation reference design.

In our implementation, we are using differential excitation on the transmit side and single-ended reception on the receive side. Functionally, the system works as expected; however, during validation we observed the following issues:

1. Delta-TOF at zero flow is relatively large,

2. The zero-flow Delta-TOF shows noticeable drift over temperature, especially at high and low temperature extremes.

At this stage, we suspect that the dominant contributors may be related to PCB layout and grounding of the receive path, particularly the way the receive transducer is referenced to ground. However, we are not fully confident about the optimal grounding and routing strategy in this mixed differential-TX / single-ended-RX configuration.

Therefore, we would like to kindly ask for your guidance on the following points:

1. PCB layout and routing recommendations

   • For a design based on SNAA284A-style differential excitation with MSP430FR6043, are there any recommended PCB layout practices specifically aimed at minimizing Delta-TOF offset and temperature drift?

   • In particular, how should the receive transducer ground/reference be handled to reduce sensitivity to temperature and common-mode noise?

2. Grounding strategy for the receive path

   • Should the receive transducer be connected to a solid analog ground, a quiet reference ground, or through an AC-coupled / pseudo-differential structure?

   • Are there known pitfalls in grounding or return-path design that could significantly affect zero-flow Delta-TOF stability?

3. Temperature characterization of SNAA284A

   • Has the SNAA284A reference design been evaluated over temperature with respect to Delta-TOF at zero flow?

   • If such data exists, is there any guidance or qualitative conclusion you could share regarding expected zero-flow drift versus temperature?

We would greatly appreciate any insights, layout guidelines, or application notes you could share.
Thank you very much for your time and support.

Best regards,
Gexiang Li