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TPS54228: Output voltage behavior with wrong feedback resistance

Masanori Tachibana
Genius 5350 points
Part Number: TPS54228
Other Parts Discussed in Thread: TPS54428

Hi support team,

I have a question about TPS54228.
The output voltage of TPS54228 can be set by R1 and R2 according to equation (3) in the datasheet.
What is the behavior of the output voltage if the combination of R1 and R2 is set so that the output voltage exceeds 7 V?
For example,
  where VIN = 18 V, R1 = 8.25 kΩ, and R2 = 221 Ω,
the calculation will be VOUT = 29.3 V.
How does an actual IC behave?

I want to know the operation of the IC as a case study if the value of R2 is incorrectly mounted.
This is because I want to consider concerns about whether overvoltage will be applied to the subsequent circuit.

Best regards,
M. Tachibana

  • 0
    TI__Guru**** 191445 points

    Tachibana-san

    The TPS54428 is designed to have on times compatible with 7 V maximum.  Programming a higher voltage may cause the circuit not to regulate properly and/or have lower frequency and higher ripple than normal.  It is a buck converter and cannot operate with a higher output voltage than input voltage.  TI recommends that you operate the TPS54428 within the bounds of the datasheet specifications.

  • 0 in reply to JohnTucker
    Genius 5350 points

    Hi John-san,

    Thank you for your reply.

    I understand that setting the feedback resistor outside of the specification range will cause unexpected behavior.
    Of course, I have understood that the output voltage should be designed to be within the specifications.

    Sincerely,
    M. Tachibana