• State TI Thinks Resolved
  • Locked Locked
  • Replies 1 reply
  • Answers 1 answer
  • Subscribers 64 subscribers
  • Views 525 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

ESR of an LDO regulator

Sukrat Gupta
Prodigy 10 points

LDO manufactures provide a graph showing stable range of ESR values say ESR must be between 0.2 to 10 ohm with 1uf output capacitor. My question is since ESR of capacitor is function of frequency so what frequency to be considered for calculating ESR.

  • 0
    TI__Mastermind 44820 points

    HI Sukrat,

    For most LDO's the bandwidth of the error-amplifier is less than 100Khz. So when we simulate for stability for modern LDO's, we are using the minimum ESR typically around 10-20mOhm. 

    The 0.2-10 Ohm range you mention seems to be referring to an older generation of LDO's and linear regulators. Their bandwidth was a bit lower and they had a higher dependence on ESR to ensure stability. Example PSRR plots between and LM1117 and its modern replacement the TLV761 shown below. The point circled is the approximate bandwidth of the error amplifier. This is where the slope of the PSRR curve changes slope. The peak you see around 2MHZ on the TLV761 plot is due to the output capacitor. 

    I hope this helps.