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TRS3223QPWRQ1 issue (TX not working)

Mayur Vernekar
Prodigy 10 points

We have some issue with TRS3223QPWRQ1, in our STP project

 

Below is the circuit for RS232 communication where TRS3223QPWRQ1 is used

 Image (1)

 

 

Issue is, when Outside device (RS232 device) is connected to TXD and RXD, and if some send data via uC_Tx (DIN1), the Data is not reflecting at DOUT1 (TXD)

 

For your information – EN =LOW, FORCEOFF = HIGH (FORCEON = LOW, Pulled Down with resistor)

 

But when there is no RS232 device or if its connected to PC (for communication check) – TXD is working fine

 

Our doubt, TRS3223QPWRQ1 is going to Auto-Power Down mode


from datasheet :

 Image(2)

  1. What is Valid RS232 signal (RXD)
  2. Can you please let us know how to overcome the Auto-PowerDown mode ?
    one thing, we can do is to make FORCEON = HIGH (but it will cause design/layout change – and right now we are not into Layout change)
  3. What if FORCEON is Floating/Not connected? Will it increase the current consumption in sleep mode (EN = HIGH and FORCEOFF = LOW) ?

 

 

Please reply on urgent basis

  • 0
    Guru 317370 points

    1. A valid RS-232 signal is high or low (more than ±3 V). When idle, the state should be logic 1, i.e., negative voltage.

    2. There is no pin-compatible device without auto powerdown. The auto-powerdown mode is designed for PC RS-232 ports that are always active. If you cannot change your board, then your outside device must be changed to always drive valid RS-232 voltages.

    3. The control input pins like FORCEON are plain CMOS inputs and must never be left floating; their state will be random or might be oscillating, and this will increase power consumption. (See [FAQ] How does a slow or floating input affect a CMOS device?)

  • 0
    TI__Guru 52462 points

    Hi Mayur,

    Clemens is correct on all points - the best option is going to be to tie FORCEON high to ensure that the device doesn't enter power-down mode as there is no P2P parts without auto power-down pins - as any other option would be a more significant change.

    Please let me know if you have any other questions!

    Best,

    Parker Dodson