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TXB0104-Q1: Power Calculation

Gkarthik
Prodigy 100 points

Part Number: TXB0104-Q1

Hi,

I am Using the TXB0104-Q1 device for VCCA = 3.3V and VCCB= 5V. I am trying to calculate the power dissipation of the device. In the datasheet the parameter " Power Dissipation Capacitance" CpdA and CpdB are given.

Should the Static Power be calculated seperately for VCCA and VCCB?

I do not have any external load capacitance connected in my design. 

What is that external load capacitance used for?

What is the maximum Power dissipation rated?

Regards

Gayathri

  • 0
    TI__Mastermind 48195 points
    Hi Gayathri,

    Yes the DC power should be calculated for both supplies. When you say external load capacitance, are you referring to the Cpd? The power dissipation is limited by the thermal ratings of the device. I am linking an application report over calculating power dissipation below.

    www.ti.com/.../scaa035b.pdf
  • 0 in reply to Dylan Hubbard
    Prodigy 100 points

    Thanks for your response.

    I have gone through the app Note and have few more questions

    Please confirm if my understanding is correct.

    1. For Static Power consumption:

    The Power consumption is calculated by product of device leakage current and supply voltage.

    To calculate the leakage current (ICC), both the sum of diode leakage current (Ilkg) and ICCA from the datasheet should be considered?

    2. Dynamic Power Consumption:

    It is calculated with transient power consumption (PT), and capacitive-load power consumption (PL).

    In my design, there is no external load capacitance added to the signals. Do I still need to calculate the Capacitive Load power consumption?

    Please explain how the dynamic power should be calculated for my case?

    Why is an external load capacitance required?

    I understand that CMOS devices has low power consumption. But how much is that maximum power rated for ?

    In datasheet, the values for Cpd is given in Page 9. what is that mean?

    Please provide your answers for all the queries.

    Regards

    Gayathri

  • 0 in reply to Gkarthik
    TI__Guru 64120 points
    Gayathri,

    The static power consumption will be minimal when the device is actively switching. This will be the product of Icc and Vcc.
    The leakage current is into or out of the device IO pins or the input pins.

    The Cpd is the power dissipation capacitance to sum up the overall internal capacitance of the FETs.
    There will be a small external load capacitance from the board traces, the device pin IO capacitance etc which needs to be taken into consideration.