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THVD1551: schematic check and common mode choke selection

Part Number: THVD1551
Other Parts Discussed in Thread: TPD1E10B06

Hi team,

Could you please help check the schematic as below?

The data frequency is 1~10MHz.

And is it OK by adding common choke in the red square area because the application is motor driver and with may noise.

Do you have common choke selection guide or common choke recommendation?

Thank you!

  • Hello Zoe,

    This schematic looks good to me. Note that the TPD1E10B06 will break down at 6 V, so you should make sure that normal operating voltages for the RS-485 bus are within this range. (I mention this because it may limit the ground potential variation that could be supported - most RS-485 buses are specified over a voltage range from -7 V to +12 V.)

    Common mode chokes are OK to include on the signal lines - just make sure that they are specified to have low impedance to differential-mode signaling across a frequency range that supports your data rate. They are effective for filtering EMI, although you may find that it is not needed in this application - the THVD15xx devices were designed to have excellent common-mode noise rejection and output emissions so that they would be suitable for applications like motor drivers/encoders. (You can reference this design for more info: www.ti.com/.../tida-01401). To save cost, then, you may want to include the option to bypass the choke using 0-Ohm resistors so that you can uninstall it if you determine it to not be needed.

    Regards,
    Max