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TPS552872: Can I use VCC for FPWM mode?

Nam, Dino
Expert 6445 points
Part Number: TPS552872

Tool/software:

Dear team, 

The customer would like to use TPS552872 for their application. 

- Input 4.5V ~ 32V

- output :7V/1A 

- FPWM mode 

The customer want to set FPWM mode but there is no external power rail to input logic high voltage for Mode port. 

Can we use VCC output to set logic high voltage on mode port? If the customer connect VCC to mode pin, FPWM mode operate well? 

If not, is there any way to set FPWM mode?  

Please let me know your opinion. 

Thank you. 

  • 0
    TI__Genius 14950 points

    Hi Nam,

    Yes, customer can directly connect MODE to VCC to choose FPWM mode. Customer can refer to EVM design.

    Regards,

    Mulin

  • 0 in reply to Mulin Yuan
    TI__Expert 6445 points

    Hello Mulin, 

    Thank you for your comment. some more questions.

    - Input 4.5V ~ 32V

    - output :6V/1A 

    Please review below customer question and let me know your opinion. 

    1. I know VCC output is 5.2V , If the input voltage down to 4.5V , What is a VCC output? Is there a bypass function input to output? 

    2. Once input voltage is 4.5V and output voltage is 6V , VCC power supply is Vout. Is it right? 

      - If yes, When the customer directly connect MODE to VCC, FPWM function operate well? 

      - First, If the input voltage 4.5V is injected, VCC power supply is Vin => regulated 6V output => VCC power supply switch to Vout. Is my understanding right? 

    Thank you. 

  • +1 in reply to Nam, Dino
    TI__Genius 14950 points

    Hi Dino,

    Nam, Dino said:
    1. I know VCC output is 5.2V , If the input voltage down to 4.5V , What is a VCC output? Is there a bypass function input to output? 

    Do you mean during start up, Vout is not ready? VCC will directly be powered by Vin and it is 4.5V.

    Nam, Dino said:
    2. Once input voltage is 4.5V and output voltage is 6V , VCC power supply is Vout. Is it right? 

    Yes. when Vout reaches 6V, VCC will be powered by Vout and output 5.2V.

    Nam, Dino said:
    - If yes, When the customer directly connect MODE to VCC, FPWM function operate well? 

    The mode pin high voltage threshold is 1.2V. So FPWM function is ok.

    Nam, Dino said:

    First, If the input voltage 4.5V is injected, VCC power supply is Vin => regulated 6V output => VCC power supply switch to Vout. Is my understanding right? 

    Before Vout reaches 4.5V, VCC=Vin=4.5V. When Vout reaches 4.5V, VCC will follow Vout, ramping from 4.5V to 5.2V. When Vout exceeds 5.2V, VCC will be stable at 5.2V.

    Regards,

    Mulin

  • 0 in reply to Mulin Yuan
    TI__Expert 6445 points

    Hello Mulin, 

    Thank you very much.