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Original question:

THVD1400: High current consumption

THVD1400: current consumption on the IC

Michael Akiva
Prodigy 65 points
Part Number: THVD1400

Tool/software:

Hi 

I am using this THVD chip and I am trying to reduce current on my design. 

currently I have 1mA current flowing through R44. even when there is no power on the RS485. 

I was trying some solution in order to reduce those currents. I tried to add pull up to R44, that reduced my currents to 150uA. 

I am still trying to reduce the currents to about 40uA top. 

I also tried a diode but that blocked my RX and it didn't work properly. 

is there a way to reduce the current flowing to the R44? 

thank you,

Michael

0564.5VDC+RS485.pdf

  • 0
    Guru 313940 points

    When the transceiver is powered off, no current should flow into or out of the R pin.
    When the receiver is enabled, the R output drives as much current as is needed for the load. What else is connected to this line?

  • 0
    TI__Guru 68580 points

    As Clemens pointed out, the R pin acts as a push pull output when it's active. If you aren't reading data then you should be able to disable the RE# pin to put it in a lower power state. 

    There shouldn't be much leakage current when the R pin is disabled. If you are seeing current pull from the R pin and modifying the R44 changes it then the R pin is acting as an active output.

    You can probably lower the current by removing the Green LED on the RS485_DIR pin if that is your ultimate goal, or making the external fail safe resistors on A/B pins a little larger.

    Ultimately, the best way to lower the R output current is disabling the R output using RE#. Otherwise you can try to size the R44 resistor larger but that will slow down the data that Routput generates when it is active.

    -Bobby