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TCA6416A

edward fulton
Prodigy 10 points
Other Parts Discussed in Thread: TCA6416A

I am using the TCA6416A on a battery power device. I am trying to get to the 3uA standby current,  With the I/O configured as outputs I can get down to 260uA. When I configured the i/o as inputs the current jumped to 550uA.  I have the following configuration:

SDA and SCL are high (no clock)

address is high

reset is high

If I look across the resistors hooked to the i/o pins I see no drop across the resistors.  I have VCCi and VCCP hooked together though a current meter to vcc  

  • 0
    TI__Intellectual 2020 points

    Hi Edward,

    Can you supply a schematic of the entire setup of the TCA6416A along with the voltage of VCCi and VCCp.

    Regards,
    Chris Kraft 

  • 0 in reply to Chris Kraft
    Prodigy 90 points

    Hi Chris,

    I am not allowed to post schematics to a forum, however I sent a copy to Thomas.Mathews@ti.com this afternoon. If you could get it from him to review without posting it.    I have to be careful the IP belongs to customer, i am just doing "work for hire". 

  • 0 in reply to Jeff Wittrock
    TI__Intellectual 2020 points

    Hi Jeff,

    One possibility is that the ports that are left floating are causing shoot through current on the input buffer. To see if this is a problem, set all the floating ports to be outputs and all the ports with a defined state to inputs. Also, ensure that you are taking the current measurement while the I2C bus is idle.

    Please let me know the outcome of the above test.

    Regards,
    Chris Kraft 

  • 0 in reply to Chris Kraft
    Prodigy 90 points

    Hi Chris,

    When I am measuring current, The micro is asleep, Both SDA and SCL are pullup to a high through the external resistors.

      I have 3.5 volts on VCCp and VCCi I have them tied together through the current meter

    Sda, scl, reset and address are pulled high.

    So are you saying it I have I/O configured as inputs but the inputs are open I will draw current through the chip?

    Ed

    Ed

  • 0 in reply to Jeff Wittrock
    TI__Intellectual 2020 points

    Hi Ed,

    Yes this is a possibility. Without a defined state, the inputs will float to an undefined voltage and worst case would be if the inputs float to midrail. A floating input will cause the input buffers to draw excessive leakage current, and it can also cause the interrupt detection logic to run unnecessarily. By setting the floating ports to outputs, the voltage at the ports will be defined and if the current drops you will be able to determine if what I described above is happening.

    Regards,
    Chris Kraft 

  • 0 in reply to Chris Kraft
    TI__Intellectual 860 points

    I should be possible to determine if the floating inputs are the cause by pulling those pins up to a Vcc rail that is not included in the current measurement (for experiment purpose only).