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TPS61165: Minimum PWM dimming frequency

Attila Varhelyi
Intellectual 615 points
Part Number: TPS61165

Product datasheet is taking about different values of minimum PWM dimming frequencies.

I would like to clarify, which is right and which is typo.

1. Datasheet says, min PWM freq is 5kHz in 7.2 Recommended Operating Conditions

https://www.ti.com/lit/ds/symlink/tps61165.pdf?ts=1664957841689#page=4

2. Datasheet says, min PWM freq is 6.5kHz: "PWM dimming frequency in the range of 6.5 kHz to 100 kHz. " 

https://www.ti.com/lit/ds/symlink/tps61165.pdf?ts=1664957841689#page=14

3. Datasheet says in 9.2.1.2.1 LED Brightness Dimming Mode Selection: "To ensure not to enter EasyScale mode, please make sure CTRL pin is never held low for more than 160us."

Is time of 160us typo, are you thinking to 260us as tes_det?

https://www.ti.com/lit/ds/symlink/tps61165.pdf?ts=1664957841689#page=12

4. Revision History says: "Changed 5 khz to 6.5 khz in first paragraph after Figure 10 "

My comment:

As I understand the operation of this chip, in theoritical, fpwm>1/260us (f>3.85kHz) could quarantee this low level on any duty cycles, so any freq above this value can provide the suitable operation.

Reference:

TPS61165 High-Brightness, White LED Driver in WSON and SOT-23 Packages datasheet (Rev. E) (ti.com)

https://www.ti.com/lit/ds/symlink/tps61165.pdf?ts=1664957841689

  • 0
    TI__Mastermind 31600 points

    Hi Attila,

    Thanks for your comments. I agree that 260us is the tes_det.

    BR

    Patrick

  • 0 in reply to Patrick Yao
    Intellectual 615 points

    Hi,

    No response for my questions. Definition of tes_det is already described in datasheet.

    The main points are

    - why TI's talkes about 160us timing?
    - why TI's talkes about min freq of 5kHz and 6.5kHz together for one parameter?
    - why TI's talkes about different values?
    - why is not PWM min freq of 3.85kHz, to avoid easyscale mode?

  • 0 in reply to Attila Varhelyi
    TI__Mastermind 31600 points

    Hi Attila,

    I'll check this with our system engineer first.

    BR

    Patrick

  • +1 in reply to Attila Varhelyi
    TI__Mastermind 31600 points

    Hi Attila,

    1. Because the minimum value of tes_det is 260us, considering some margin, we suggest CTRL pin not held low for more than 160us to avoid entering EasyScale mode unexpectedly.

    2. Theoretically if the PWM frequency is larger than 3.85kHz, device won't enter EasyScale mode by mistake with any PWM duty cycle. But as mentioned before, we suggest a larger "minimum PWM frequency". So actually, 5kHz and 6.5kHz are not the really minimum PWM frequency but with some margin as well.

    Sorry for the misunderstanding; we'll improve the description in datasheet in future revision.

    BR

    Patrick