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LP3964: At what frequencies are the capacitor parameters critical?

Eric Raguzin
Prodigy 130 points
Part Number: LP3964

I'm reading through the datasheet here and Section 8.2.2.1 describes the ESR requirements of the input and output capacitors. For example:

CIN ESR (mΩ) / CIN (μF) ≤ 1.5

0.2 Ω ≤ COUT ESR ≤ 5 Ω

However, what at what frequencies do these relationships need to be valid for both C and ESR? 100 kHz or less? 10 kHz or less?

  • +1
    TI__Genius 12511 points

    Hi Eric,

    When talking about the ESR for control loop stability, this means that the frequencies that would be covered would be the frequencies of the control loop itself. These frequencies are typically 100Hz -500kHz for modern high bandwidth devices.

    For this device which is a little older using different design techniques the critical regions would be tighter at roughly 100Hz - 100kHz. But using something that is within the specified ranges for even wider frequency bands will give the control loop more margin and optimize performance.

    Regards,

    John