• State TI Thinks Resolved
  • Locked Locked
  • Replies 4 replies
  • Answers 1 answer
  • Subscribers 35 subscribers
  • Views 130 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TCA9803: TCA9803

Silvas Melshia
Prodigy 50 points

Part Number: TCA9803

Hi,

Can you please share the power dissipation value for this part

  • 0
    TI__Guru 53491 points

    Hi Silvas,

    Today is a TI holiday, please allow some time for response. 

    Thanks,
    Jack

  • 0
    TI__Guru 60108 points

    Hi Silvas,

    The power dissipation for this buffer would be determined by the pull-up resistors used on A-side and the voltages used for VCCA and VCCB, do we have this information? 

    The power dissipation is worst case when the buffer is constantly driving a logic low from B-side to A-side. This is not the normal use of the part since this will be buffering I2C signals most of the time. 

    Regards,

    Tyler

  • 0 in reply to Tyler Townsend
    Prodigy 50 points

    Hi Tyler,

    Thanks for you reply.

    We are using VCCA as 1.8V logic and VCCB  as 3.3V logic for this buffer. On the A side we are using the Pull up resistors of 4.7K ohm.

    What is the worst case for considering the power dissipation of this part TCA9803? Kindly update us

  • 0 in reply to Silvas Melshia
    TI__Guru 60108 points

    Hi Silvas,

    The worst case power consumption is when SDAA = SCLA = low. There will be some power consumption by your open-drain driver (from target or MCU) that will sink the current from the pull-up resistors on A-side. This however does not factor into the power consumption of the buffer. 

    I assume there are no pull-up resistors on B-side of the buffer, as this is the proper use of the buffer relying only on the internal current source which has a typical current of 3.3 mA pull-up current for TCA9803. 

    A majority of the current will be through ICCB supply. There is some current from ICCA. 

    Ptotal = (ICCA)(1.8V) + (ICCB)(3.3V) = ~(7.9mA)(3.3V) = 26.07 mW. 

    This is the DC state if A-side is held low. In practice, I2C will run a logic low only for short periods of time (microseconds of time) for each I2C transaction. You will dissipate more power overtime the more times that the device drives a low. 

    In the Idle state when both sides are high, the quiescent supply current drops. You can expect much less power dissipation: 

    Ptotal(idle) = (1.8V x 8uA) + (3.3V x 90 uA) = 0.0144 mW + 0.297 mW = 0.3114 mW

    Regards,

    Tyler