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TPS61169 - About VFB of linearity at low Duty

Hide
Guru 21045 points
Other Parts Discussed in Thread: TPS61169

Hi Team,

 

Our customer worry about VFB of linearity at low Duty.

Because, they worry whether the offset of internal GM Amplifier have a bad influence to VFB at low duty.

I understand that TPS61169 has VFB of linearity at PWM dimming signal duty cycle is from 1% to 100%.

Is my understanding correct?

If no, could you please let us know the range of PWM dimming signal duty cycle that TPS61169 can maintain the VFB of linearity?

 

[Conditions]

-VIN=2.0V to 4.2V

-VOUT= Around 24.5V (7LEDs (Vf=3.5V))

-RSET=6.8kohm (ILED=30mA at Duty=100%)

-ILED=less than 1mA to 30mA

-Duty=1% to 100%

-L=4.7uH

 



 

Regards,

Kanemaru

  • 0
    TI__Intellectual 2090 points
    Hello Kanemaru,

    Yes, your understanding is correct.
    The TPS61169 VFB Linearity is specified from 1% to 100% PWM Duty Cycle.
    Let me know if you need additional information regarding the customers concern.

    Best regards,
    Randy
  • 0 in reply to Randy Dahl
    Guru 21045 points

    Hi Randy-san,

     

    Thank you for your response.

    I have one more question.

    I would like to know VREF accuracy at Duty = 10% to 99%.

    Could you please let us know it if “VREF accuracy at Duty=10% to 99%” and “VREF accuracy at Duty=100%” are different?

     


     

    Regards,

    Kanemaru

  • 0 in reply to Hide
    TI__Intellectual 2090 points
    Hello Kanemaru-san,

    There is not any difference between VREF accuracy 10% to 99% and 10% to 100%.

    Best regards,
    Randy
  • 0 in reply to Randy Dahl
    Guru 21045 points

    Hi Randy-san,

    Thank you for your prompt reply.

    I understand. Thank you very much.

    Regards,

    Kanemaru

  • 0 in reply to Hide
    Guru 21045 points

    Hi Randy-san,

     

    Thank you always for your kind support.

    I have one more question.

     

    I understand that VREF is 188mV(min), 204mV(typ), 220mV(max) if TA is 25℃ to 85℃.

    (I referred to the datasheet.)


     

    However, our customer would like to know the accuracy of VREF at TA is “-30℃ to 25℃”.

    Because, they will use TPS61169 at TA is -30℃ to 85℃ , Duty is 1% to 100%.

    Could you please let us know if you have any information?

     

    Regards,

    Kanemaru