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LM1085 - STABILITY with load/decoupling ceramic capacitor

Danny Palmer
Prodigy 10 points
Other Parts Discussed in Thread: LM1085

The data sheet says specifically to use "load/decoupling capacitance of 10uF tantalum or a 50uF aluminum".

Technology today has changed and ceramic capacitors should be able to be used for this application - better ESL/ESR.

Can anyone give their opinion on this? Obviously the drive for this is price - Tantalum is still much more expensive than ceramic.

  • 0
    TI__Mastermind 22610 points

    Yes, technology today is different, but the LM1085 internal design is still the original circa 1998. The ESR in the LM1085 output capacitance is a requirement for output stability.

    There are numerous other, more modern, linear regulators that are designed to work specifically with low ESR ceramic capacitors.

    However, if using LM1085 with ceramic Cout is needed then please refer to the Application Report:

          SLVA214A - Ceramic Capacitors Replace Tantalum Capacitors in LDOs

          http://www.ti.com/lit/an/slva214a/slva214a.pdf

    Basically, you are simulating the required Cout ESR with a discrete, low value, series resistance.