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TPS6521905: What is the output capacitance of the TPS6521905?

Takashi Sato
Prodigy 60 points
Part Number: TPS6521905

Tool/software:

The following description is found in the “Table 8-1. Buck output capacitance” section of the datasheet

MAX (Includes local + point of load)

I have two questions about this statement

(1) What does “point of load” mean?
Does it refer to the noise limiter capacitor used in the LSI that uses the power supply generated by the TPS6521905?

(2) What kind of problem will occur if I install a capacitor that exceeds the Max Capacitanse shown in Table 8-1?

Best regards.

  • 0
    TI__Mastermind 22336 points

    Hi,

    Thank You for using E2E. Please find the responses below and let us know if there are any questions.

    • "point of load capacitance" refers to the capacitance that is placed close to the load. For example: if PMIC is powering a processor, the "point of load" capacitance would refer to the capacitors that are placed close to the processor pin. 

     

    • If the capacitance does not meet the PMIC spec, the stability could get affected. The more you deviate from the capacitance spec, the more the phase margin drops and the load transient performance decreases. 

    Thanks,

    Brenda

  • +1 in reply to Brenda Diaz
    Prodigy 60 points

    Thank you for your answer.
    I have one additional question.

    Is the Capacitance (Min/Max) listed in Table 8-1 a value for each individual Buck?
    Or is it the sum of Buck1, Buck2, and Buck3?

    For example, the Max value of COUT_HIGH_BW is 220uF,
    Does this mean Buck1:220uF, Buck2:220uF, Buck3:220uF (total 660uF)?
    Or does it mean that the total of Buck1+Buck2+Buck3 is 220uF?

    Best regards.

  • +1 in reply to Takashi Sato
    TI__Genius 10772 points

    Hi Takashi,

    Due to the holiday in the US, many of the device experts are currently out of the office. When they return they will look into this and provide a response. Please expect some delay accordingly.

    Thanks,
    Field

  • 0 in reply to Takashi Sato
    TI__Mastermind 22336 points

    The Min/Max capacitance values specified in the table below are for each individual Buck. For example: if Buck1 is configured as Quasi-fixed frequency and high bandwidth, then 30uF would be the minimum required local output capacitance on Buck1. 

    Thanks,

    Brenda