• State TI Thinks Resolved
  • Locked Locked
  • Replies 5 replies
  • Answers 3 answers
  • Subscribers 64 subscribers
  • Views 814 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.

TPS61194-Q1: Which PWM frequency do you Recommend?

Amelie Zheng
Genius 10865 points
Part Number: TPS61194-Q1

Hi Team,

The frequency that 61194 supports PWM is 100HZ~20kHZ. What is the recommended frequency for use in the car display? At present, customer use 200Hz, measuring the power supply input power ripple is large--350mV, as shown below. yellow is VIN_12V voltage, green is PWM signal.

In the reference design, it is recommended to use ceramic + electrolytic capacitors for the input and output terminals. What is the main function of the 33UF electrolytic capacitors here? Can it be eliminated or replaced with ceramic capacitors when space is limited?

  • 0
    TI__Genius 11836 points

    Hi Amelie,

    The frequency that 61194 supports PWM is 100HZ~20kHZ. What is the recommended frequency for use in the car display? At present, customer use 200Hz, measuring the power supply input power ripple is large--350mV, as shown below. yellow is VIN_12V voltage, green is PWM signal.

    It's OK if 200Hz generates no noise.

    In the reference design, it is recommended to use ceramic + electrolytic capacitors for the input and output terminals. What is the main function of the 33UF electrolytic capacitors here? Can it be eliminated or replaced with ceramic capacitors when space is limited?

    As long as the 2 × VIN MAX or more voltage rating and the value of capacitor under this frequency(Tab 2 in the datasheet) are met, it's OK to use ceramic capacitors.

  • 0 in reply to Charles-Chen
    TI__Genius 10865 points

    Hi Charles,

    thanks for your reply.


    Which frequency is the most commonly used? 

  • 0 in reply to Amelie Zheng
    TI__Genius 11836 points

    Hi Amelie,

    If there is no noise, you can use 200 Hz to obtain high dimming ratio.(The lower PWM frequency, the higher dimming ratio).

    However, if there is noise at low PWM frequency. You can raise your PWM frequency and the final value is up to actual situation.

  • 0 in reply to Charles-Chen
    Prodigy 10 points

        Hi Charles,

                   Tab 2 in the datasheet，At 400KHZ switching frequency, it is recommended to use it 2x10(cer.)+33(electr.). Can it be replaced by a 53UF ceramic capacitor?

  • 0 in reply to user5343043
    TI__Genius 11836 points

    Hi sir,

    You need to consider the derating of ceramic capacitor with voltage and I suggest the minimum value of output capacitor should at least be 33uF considering the derating of ceramic capacitor. And you also need to verify the loop stability after replacing the capacitor.