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THVD1400: High current consumption

Michael Akiva
Prodigy 65 points
Part Number: THVD1400

Tool/software:

Hi, 

I am using THVD1400 for RS485 communication between my device. 

I have the following schematics - 

5VDC+RS485.pdf

I have a current issue when I start communicating with the device. 

the datasheet mention about 1mA consumption when the device is on -

but in fact, I see other currents when I measure VCC. 

When the driver enabled, Receiver disabled - 57mA

When the driver disabled, Receiver enabled - 22mA  

When the driver disabled, Receiver disabled - 8uA  

I want to further understand why that happens because I am using battery and I can afford such currents. 

Thank you,

Michael. 

  • 0
    Guru 313920 points

    The datasheet values are measure without a load.

    The fail-safe resistors (R45/R49) are not necessary (or can be weaker) if all receivers on the bus have fail-safe inputs.

    For slow signals, consider AC termination. For a very short bus, termination might not be necessary.

  • 0 in reply to Clemens Ladisch
    Prodigy 65 points

    Hi,

    thank you for your fast reply. 

    what should be the current when there is load? it can go as high as 57mA ? 

    R45/R49 are un-assembled. 

    what is "slow signal" ? 115200 baud rate is slow ? 

    AC termination can decrease the currents? 

    thank you,

    Michael

  • 0 in reply to Michael Akiva
    Guru 313920 points

    The load current depends on the load. To measure the bus current, check the voltage drop over the termination resistor.

    Yes, 0.1 Mbps is very slow.

    AC termination removes DC currents. But the R and C form a low-pass filter.