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SN65HVD06: How to calculate power budget for RS-485 interface

John11513
Expert 5480 points
Part Number: SN65HVD06
Other Parts Discussed in Thread: ISOW7842

Hi team,

My customer is designing isolated RS485 interface with ISOW7842 + multiple SN65HVD06. I do not know how to do power budget for each RS-485 TRX IC. To support 2.5V out on 54ohn bus load it needs 46mA of power supply current. While a typical RS-485 interface is assumed to support 60mA driver output. And and the driver typically has 250mA current limitation when in bus short condition. I am not sure how should customer do power budget for each RS-485 TRX IC? (Considering multiple RS-485 TRX ICs are powered by a single power supply such as output of ISOW7842.)

Thank you,

John

  • 0
    TI__Mastermind 25705 points

    John,

    You can use Fig. 15 on the datasheet to estimate the power consumption. If the data rate of your application is high, please take the capacitive load into account. The detailed calculation is discussed in this blog. 250mA is the current limit in fault condition, which you don't need to worry in normal operation. If there are more than one RS-485 transceivers powered by the same supply, please pay attention to the ones driving the bus. Usually the power consumption in the receiver mode is low. Please let me know if you have further questions.

    Regards,

    Hao