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TPS709xx Cout ESR Requirements

Other Parts Discussed in Thread: TPS709

The data sheet for the TPS709 linear regulator specifies that the ESR of the output capacitor should be less than 0.2Ω for stability.

This requirement seems to be underspecified since ESR is dependent upon frequency. If the frequency of interest is 1kHz then there are very few ceramics that are below the requirement. On the other hand, if the frequency is 100kHz then every ceramic capacitor available is far below 0.2Ω making the requirement seem superfluous.

I may be misunderstanding something, but if not, within what frequency range does the capacitor need to meet this requirement?

  • Hi ,

    The ESR is needed for the small signal control loop crossover. You can estimate the crossover frequency by continuing the 20dB/decade decay on the PSRR plot to where it crosses 0.

    As this LDO was designed to be stable with ceramic capacitors, it does make sense that ceramic capacitors do not have an issue fulfilling the ESR requirements. The ESR requirements are stated in the event that capacitors other than ceramic are used.

    Very Respectfully,
    Ryan