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TCA9554: standby mode/power consumption

Connie Lu1
Intellectual 2125 points
Part Number: TCA9554

Hi team,

My customer plan to use TCA9554 at 1.8V VDD and have a few questions.

  1. As I understand standby mode is entered automatically when there is no transaction on I2C. What is the state of I/Os during standby?
  2. What is the current consumption if the I/Os are set to output and tristate ? It is not clear in the datasheet.
  3. Why is the current consumption much higher when i2c=0khz and Vi=0 and I/Os are set to input? Is it assuming internal pull ups enabled? What is the current consumption internal pull ups are disabled and Vi=0

Thanks,

Connie

  • +1
    TI__Guru 51635 points

    Hi Connie,

    1. Standby mode is a way to classify the current required by the I2C state machine for this device. This is independent from the current required to drive any I/O ports. The I/O ports can be configured using the I2C interface by writing to the device's configuration register. The I/O ports will remain configured according to this register until the register values are changed or the device is reset, where the register returns to its default value. 

    2. The current consumption of the I/O ports will depend on their configuration and the load presented to them. While configured as an input, the 100k-ohm internal pull-up resistor to Vcc will remain active. This means that if the input voltage is at Vcc potential, there will be very minimal current draw from this pin. 
    When configured as an output, the pin will either be biased strongly to Vcc or Ground. The amount of current needed by this pin will depend to the connected load. 
    There is no dedicated tri-state for the I/O pins. The highest-impedance state while operational will be with the pin configured as an input, in which case the 100k-ohm internal pull-up is still active. 

    3. You are correct that this consumption is due to an internal pull-up. This pull-up cannot be disabled. If a low-power idle mode is desirable, the pins should be configured as inputs with the input state remaining at Vcc nominally for minimal leakage. 

    You may review the simplified I/O pin schematic shown in datasheet Figure 15. 

    Let me know if you have any more questions.

    Regards,
    Eric Schott