• State TI Thinks Resolved
  • Locked Locked
  • Replies 4 replies
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 876 views
  • Users 0 members are here
Support feedback
Options
Options
Related

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.

TPS54201: PWM dimming control

na na78
Guru 16770 points
Part Number: TPS54201

Hi

We suppose to do PWM dimming operation.

PWM signal is 5V.

1.

PWM pin has internal pull down inside, but I could not get pull down resistor value from datasheet.

What resistor value should be added to enter PWM dimming mode if PWM input is 5V?

2.

Is it impossible to support PWM whose frequency is 5KHz?

BestRegards

  • 0
    Guru 16770 points
    Hi

    I think the voltage peak of PWM should be between 1.1V and 1.97V for PWM dimming.

    Can we use equation (2) to set PWM peak?

    For example,
    MCU output = 5V pwm, VPWM = 1.5V is assumed.

    RTOP = ( 5V/1.5V - 1) * 10K = 23.3K

    I appreciate if you could reply.

    BestRegards
  • 0 in reply to na na78
    TI__Intellectual 950 points
    Hi,
    I am a little confused which resistor we are talking about. Could you draw a simple graph to show the circuit?
    Thanks,
    BRs,
    Rosley
  • 0 in reply to Rosley Ge
    Guru 16770 points

    Hi Rosley

    Thank you for your reply.

    I could see following explanation in 7.4.1 Enable and Disable Device.

    "PWM pin has internal pull-down resistor, floating this pin will disable the device."

    And this resistor at PWM pin would be shown at left side in Figure 17.

    The PWM signal is 5V from MCU, so I think the PWM voltage should be divided to be detected as PWM dimming operation.

    However, I don't know how to divide 5V with what resistor value.

    BestRegards

  • 0 in reply to na na78
    TI__Intellectual 950 points
    Hi
    Internal pull-down resistor is a big one. It should be something like hundred Kohm. I don't think it will affect your calculation of divided resistor.
    Thanks,
    BRs,
    Rosley