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RS232 DB9 transceivers with internal charge pump and EVM?

Matt Mitchell46
Intellectual 560 points
Other Parts Discussed in Thread: TRS3253E, TRS3232, MAX3223, MAX202

Hi,

We have an application where a 1.8V to 3.3V board talks to PC via RS-232. The signal is a subset of the DB9 which consists of TXD,RXD,RTS,CTS.

As the voltage needs to be translated to 15V level to communicate with PC, and down to 1.8-3.3V level when back, does any transceiver integrates internal DC converter/charge pump to do this?

Please recommend three to four modules for us, thanks!

And please also point out if any of them has EVM available. It is preferably that the EVM has input and output headers (allow inserting wires/connectors from other boards) for readily serving as a voltage bridge between low-voltage board and PC.

 

Matt

  • 0
    TI__Guru*** 140106 points

    Matt,

    We have many RS232 devices that run from 3.3V supply that generate greater than +/-5V driver output. Four external capacitors are required. Did you know that a +/-15V driver will run slower speed due to 30V/uS RS232 maximum slew rate? A high voltage driver also consumes a lot more power.

    Our TRS3253E includes internal voltage translation for 1.8V logic.
    Our TRS3232 and MAX3223 support single 3.3V supply and have 2 drivers and 2 receivers.
    Higher ESD versions and faster versions are also available.

    There is no EVM available.

  • 0 in reply to Ron Michallick
    Intellectual 560 points
    Ron,

    I did looked at all three but none raises to plus/minus 15V.

    I did run test on PC with boards from other manufacturer and 15V on the PC end succeeded in communication. I don't if 5V will work (not certain about standard). Could you confirm on this?

    Also, do you have straight 15V output RS232 transceivers, if we could run at lower speed?


    Matt
  • 0 in reply to Matt Mitchell46
    TI__Guru*** 140106 points
    Matt,

    The RS232 standard states receivers must accept +/-3V as a valid signal. Drivers must provide at least +/-5V.
    Receivers not required to but will honor 0V input the same as -3V. This is needed to ensure a fail safe high ROUT with an open cable input.

    The MAX202 provides more output voltage, but needs a 5V supply.

    We have even higher output voltage, but these devices need three power sources. 5V, 15V and -15V.

    The +/-5.5V output is very popular today. Many use them without any issues.