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THVD1450: Current consumption at 3.3V and 50Mbps

Hans
Genius 12865 points
Part Number: THVD1450

Hello Team,

according to data sheet figure 13 the current consumption is 85mA at a data rate of 50Mbps.

With 56 Ohm termination resistor between pin A and B and a rectangular signal at the input pin D we measure 62mA.

Can you explain that difference, please?

Thanks and Best Regards,

Hans

  • 0
    TI__Guru 53515 points

    Hi Hans,

    Supply current increases with signaling rate primarily due to an increase switching frequency. Every time the driver output changes, current must be sourced from Vcc to change drive the bus accordingly. With a faster signaling rate, these current spikes occur more often and more current is drawn by the transceiver as a result. A secondary cause of power consumption is due to capacitive loading. More parasitic capacitance on the bus requires more current to drive the bus to a new state. This is modeled in our datasheet tests as a lump 50pF on the B and A lines. 

    In a test with 56-ohm loading with no capacitive load (Cl), you will see lower current draw than what is recorded in the datasheet. To better model power usage in an application with parasitics from a cable, adding this load will yield more accurate approximations. 

    Let me know if you have any more questions.

    Regards,

    Eric