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TPS28225: PWM threshold voltage

Kei Kuwahara
Expert 7660 points
Part Number: TPS28225

Hello team,

My customer wants to use TPS28225 with 3.3V of PWM input with PWM mode only.

On the datasheet, electrical characteristic table, it says LOW threshold is 1.0V and HIGH threshold is 3.8V when PWM=5V.

On 7.3.4 section, it says initially the threshold is 1.0V and 2.0V. However, the upper threshold is adjusted to 75% of the PWM voltage.
So does this mean that, if customer inputs PWM = 3.3V, the LOW threshold is fixed at 1.0V and HIGH threshold will be set to 3.3V * 0.75 = 2.475V?
Note that customer is not using 3 state mode.

Also, how many cycle does it take to adjust the HIGH threshold to 75%?

On the Figure 1, it seems like the LOW and HIGH threshold is at 50% of the PWM, is this not true?

Best Regards,
Kei Kuwahara

  • +1
    TI__Genius 14145 points

    Hey Kei,

    Thank you for your questions regarding the TPS28225.

    As for the electrical characteristics table, that is stating the operating conditions of 5V PWM, therefore the 75% threshold of that would be  the 3.75 or 3.8V which follows what is stated in Section 7.3.4 3-State Input.

    As for how many cycles would it take to adjust to that, that isn't something that is spec'd, but this operation adjustment should not affect operation after start-up. Are you looking to change PWM amplitude during operation?

    As for the Figure 1 Timing Diagram, the LOW and HIGH thresholds are indicated by the horizontal dashed lines and the propagation delay is just measured off of the 50% state.

    Let me know if you have any further questions.

    Thank you,

    William Moore