• State
  • +1 person also asked this people also asked this
  • Locked Locked
  • Replies 3 replies
  • Subscribers 65 subscribers
  • Views 249 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TPS92201: What happens with PWM below 1%?

Keith Standiford
Prodigy 10 points
Part Number: TPS92201
Other Parts Discussed in Thread: TPS92200, , TPS922052, TPS922053

I would like to be able to turn off the LED by lowering the PWM input below 1%. The data sheet for tps92201 does not specify what will happen. The TPS92200 PWM version says that holding the PWM input low will disable the chip, but I may have have spikes longer than the minimum PWM signal time even with PWM duty cycle below 1%. I am trying to use a CMOS 555 timer to make the PWM. I prefer the tps92201 for the higher speed and lower inductance. What will it do with PWM under 1%?

  • 0
    TI__Mastermind 19920 points

    Hi Keith,

    Based on my understanding, you are going to using PWM dimming and analog dimming at the same time (i.e. you need to adjust the amplitude of the output current and you also need to strobe that current). Is my understanding correct?

    Best Regards,

    Steven

  • 0
    Prodigy 10 points

    Sorry, I was confusing. I am trying to decide between analog and PWM dimming. If I choose analog with the TPS9220 analog version, I believe I can disable the chip by holding the dimming input below 0.3V. If I choose PWM dimming with the TPS92201 I can have a higher switching frequency but it looks like I have to turn enable off to disable the chip. Am I correct so far?

    Then my real question is what happens on the TPS92201 when the PWM duty cycle falls below 1%? Will it turn the output to 0, but leave the switcher on? Or would it actually disable the chip? 

    -Keith

  • 0 in reply to Keith Standiford
    TI__Mastermind 19920 points

    Hi Keith,

    Please refer to my comments below:

    Keith Standiford said:
    If I choose analog with the TPS9220 analog version, I believe I can disable the chip by holding the dimming input below 0.3V. If I choose PWM dimming with the TPS92201 I can have a higher switching frequency but it looks like I have to turn enable off to disable the chip. Am I correct so far?

    For TPS9220(0) analog version you mentioned, I think you are referring to TPS92200D2. Am I correct? If so, then your understanding is correct.

    Keith Standiford said:
    Then my real question is what happens on the TPS92201 when the PWM duty cycle falls below 1%? Will it turn the output to 0, but leave the switcher on? Or would it actually disable the chip? 

    Even if you input 0% PWM (constant-low) signal to TPS92201, there is still very small output current as the voltage of the FB pin will drift and the internal logic circuit does not completely turn the gate driver off. If you want to completely turns off the output current, you should use the EN pin to disable the device.

    Steven Li said:
    Based on my understanding, you are going to using PWM dimming and analog dimming at the same time (i.e. you need to adjust the amplitude of the output current and you also need to strobe that current). Is my understanding correct?

    I asked the above question because I want to see if there is any other device that may fit your requirements, like TPS922052 / TPS922053 :) 

    Best Regards,

    Steven