PGA460: How to using A Couple of PGA460s

Hi Kato,

Could you tell me a bit more about your application? The PGA460 is not typically used in this fashion, though it is possible. 

The way you have your block diagram set up, it looks like your transmitting PGA460 will not need to listen for a returning echo, and your receiving PGA460 will not need to burst. In this case you can make some modifications to your block diagram and use the Broadcast commands found in Table 3 on page 38 of the datasheet. The INP and INN pins of the transmitting PGA460 can be left floating and the OUTA and OUTB pins of the receiving PGA460 can be left floating. In addition, you can omit the transformer on the receiving side, which will reduce the cost of your solution. Both PGA460s should be sent the Broadcast "Burst and listen" command. Without the transformer, the receiving PGA460 will be unable to burst, and will essentially be in "Listen only" mode. However, sending both PGA460s the same command will prevent timing errors that could arise if the receiving side started listening too early. Note that this will require that both PGA460s are connected to the same UART signal. 

As for the distance between the PGA460s, this depends heavily upon the environment in which they are operating, your power budget, your PCB space, and if a low-cost or a high-performance solution is more important to you. I can provide a better idea of your expected range with this information. 

Regards,

Hi Kristin-san,

Thank you for the information.

According to your explanation, I think that the following configuration is also able to be applied, so could you please give me your advice if there is restriction on the distance or the location between the transducers ?

Best regards,
Kato

Hi Kato,

Is this an air-coupled environment? If this is a liquid-coupled environment, the TDC1000 would be more suitable for your application.

In this orientation with the PGA460s, the distance between the two transducers is not critical, but they must have overlapping fields of view. If the fields of view do not overlap, the listening transducer will not be able to detect the echo when the other transducer bursts. Angling the transducers may help create overlapping fields of view. The ability for the listening transducer to detect an echo also depends on the shape of the object you are trying to detect. Can you tell me if the object is flat or curved, and the size of the object?

In addition, the Broadcast commands I recommended previously will not work in this setup. If you use Broadcast commands in this setup, both transducers will burst simultaneously, causing interference. You would need parallel UART signals to control each PGA460 individually with your microcontroller. One PGA460 would need to be given the Single Address "Listen only" command  while the other was simultaneously given the Single Address "Burst and listen" command. If there is no way for these signals to reach the PGA460s simultaneously, errors could occur in the time-of-flight calculations. The Single Address commands are found on page 37 in Table 3 of the datasheet.

Regards,