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TCA9535: About TCA9535 for continuous PWM output control

SHENG YANG
Expert 1090 points
Part Number: TCA9535
Other Parts Discussed in Thread: TCA6507

HI.

Currently in a project application due to the limited number of GPIOs in the MCU, I would like to use the TCA9535 to expand the GPIO ports. This GPIO is used to drive a high side switch (e.g. IN port of TPS48111-Q1,) which is using a PWM output but at a frequency of about 100 HZ. By reading the link (e2e.ti.com/.../ 1211795/tca9535-could-tca9535-be-used-to-simulate-pwm-output?tisearch=e2e-sitesearch&keymatch=TCA9535#) should be possible. My question is that if I use the TCA9535 to output PWM at 100Hz, then I have to use the IIC to control the GPIO flip-flop all the time during the 10mS cycle, instead of using the MCU's GPIOs directly to set the PWM frequency and then the GPIOs will keep outputting the corresponding PWM waveforms. Is my understanding correct? Thank you.

  • 0
    Guru 244370 points

    Yes, you have to switch the output on and off from the MCU.

    It might be possible to use a LED driver like the TCA6507.

  • +1
    TI__Mastermind 49410 points

    In theory you could make this work. This will eat up your bandwidth since you will need to continuously send I2C signals to the TCA9535 and this will also use up computations on the MCU since you would need to continuously send those I2C signals to flip the bits. 

    As Clemen's pointed out, it may be simplier to try to find a device that has a PWM GPO like  TCA6507. (This one is open drain though)

    -Bobby