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TRS3122E: Interface required to work in harsh environment

Vikas Thukuntla75
Intellectual 520 points
Part Number: TRS3122E

Hi,

We are making a product that has the controller and communication modules. Controller module will be installed in a pit under the ground. Communication module will be installed over the ground. Both these modules are exposed to external harsh environment conditions. The distance between controller and communication module will be 10metre (max), and connected through a cable. The basic interface/protocol will be UART between these two modules. Due to harsh environment, we want to use a suitable cable interface that can sustain hardships posed by external environment.

With the above consideration, I have started pursuing the widely used and popular interface RS232. But I am not sure whether pursuing RS232 is the right choice. The supply voltage in both the above modules is 3.0V, and the number of drivers & receivers are 2 each. I have few doubts as below. Kindly clarify the same.

  1. Is RS232 the right interface for my above needs? If not, can you suggest any other suitable interface?
  2. Since my supply voltage requirement is 3V, I was considering the IC with its supply voltage range beyond 3V. For example, I want the IC with the range of 2.0V to 3.6V, where-in 3V falls in between. Somehow, I could not get any IC matching my above requirement. However I started looking into TRS3122E, but it also does not meet my above requirement. Can you suggest any suitable IC meeting my above requirement?

Regards,

Vikas Chandra Rao.

  • 0
    TI__Mastermind 25705 points
    Vikas,

    Can you elaborate what you mean 'harsh environment'? Does it mean high current ESD events, or high level short voltage or anything more?

    In general if your communication is single-ended, RS232 is good choice. For differential signaling, RS485/422 can be considered.

    TRS3122E can work with various supply from 1.65 V to 5.5V. Were you worried about the device behavior between 2 V to 3 V?

    Regards,
    Hao
  • 0 in reply to Hao L
    Intellectual 520 points

    Hi Hao,

    Basically, our product will be installed under the ground in a pit. The noise through the ground is mainly due to external environmental factors (like lightning, thunderstorms, etc). Sometimes, the noise can be due to interference from external factors like ESD, emissions from external EMI sources, etc. Due to these noises and our product usage, I have termed it as harsh environment. I want to ensure that the communication between the modules is reliable, and also the have suitable protections within the modules, in this harsh environment.

    Our signals within the controller and communication modules are UART, and these are single-ended. Hence I was pursuing RS232. What could be the max cable distance that I can use with RS232?

    As I understand, TRS3122E supply voltage range is 1.65V to 2V, or 3V to 3.6V, or 4.5 to 5.5V. Whereas the supply voltage that can be provided in our product is 3V. With this consideration, I was mentioning that TRS3122E is not able to meet our requirement.

    Kindly suggest suitable solution that I can pursue.

    Regards,

    Vikas Chandra Rao.

  • 0 in reply to Vikas Thukuntla75
    TI__Mastermind 25705 points

    Vikas,

    Thanks for your explanation. Do you need full duplex communication or is half duplex good enough? Do you want considering RS485? You can convert UART signal to differential signal that is immune to common mode noise. The latest RS485 transceivers have every good ESD protection features. In the system, you can use shielded cable with termination resistor to make the communication more robust. But I agree the low supply is still a challenge here.

    Back to RS232, usually it can support up to 50ft. You're right that TRS3122E cannot work with supply range from 2V to 3V.

    It looks like you may need to somehow fix the supply. High speed communication comes with low supply voltage but in industrial we haven't got there yet.

    Regards,

    Hao 

  • 0 in reply to Hao L
    Intellectual 520 points

    Hi Hao,

    I am fine with half duplex communication as well. Yes, I can consider RS485 interface if it is more robust than RS232. Can you suggest any RS485 transceiver that I can consider, preferably with supply voltage suiting my requirements?

    Regards,

    Vikas Chandra Rao.

  • 0 in reply to Vikas Thukuntla75
    TI__Mastermind 25705 points

    Vikas,

    Unfortunately the lowest supply voltage of RS485 is 3.3V. Some requirement of industrial applications like wide common range, reverse polarity protection make it hard to work with lower supply. Our latest THVD14xx (www.ti.com/.../THVD1452) can cover from 3V to 5V. If you're interested, you can request samples on TI.com.

    Regards,

    Hao