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TCA9538: TCA9538 minimized LED current consumption

Thomas Chang15933
Expert 4770 points
Part Number: TCA9538

Dear Team:

Customr confused why parallel 100 K resister can minimize current consumption in aour datasheet..

Becasue P port is set input, how can it generate voltage?

Could you eplain it detail?

  • 0
    TI__Genius 17195 points
    Hello Thomas,
    It is generally a bad practice to leave cmos inputs floating because the pin voltage can move around due to leakage currents. If the voltages falls in between Vcc and Ground it can get into a state where the both the p-fet and n-fet can conduct, thought fairly weekly, and cause excessive current consumption. I am attaching a link to app note that covers this in greater detail.

    www.ti.com/.../scba004d.pdf

    In the datasheet we tell them to put a 100 k in parallel because then you make sure the pin isn't floating. The diode can be considered a very high impedance, thus it looks like it is floating without the 100 k resistor.

    Make sense? Let me know if you have questions.
    -Francis Houde