LM1117: Output capacitor

Shinya Sawamoto

Part Number: LM1117

Hello team,

I have a couple of questions regarding output capacitor selection.

1) From the below datasheet description, we can choose higher than 10uF tantalum or E-cap. Isn't there any limitation for the maximum? (e.g. up to 100uF)
"The minimum output capacitance required by the LM1117 is 10 µF, if a tantalum capacitor is used. Any increase of the output capacitance will merely improve the loop stability and transient response."
2) Does too much output capacitor impact to the load transient performance?

Thanks in advance.
S.Sawamoto

over 3 years ago

0 JCHK over 3 years ago

TI__Mastermind 43580 points

Hi Sawamoto-san,

Please see my response to a similar question on output capacitance: https://e2e.ti.com/support/power-management/f/196/p/850954/3148292?tisearch=e2e-quicksearch&keymatch=lm1117%20cap#3148292

So for question #1, I have seen much more than 100uF at COUT for some applications. As long as the minimum load current is maintained there is no negative impact on stability.

For question #2, increasing the output capacitor certainly helps to support very fast load transients. While CIN is not essential for stability, increasing this can help to mitigate VIN dropping with excessive load current transients.

As noted in the above link, the TLV767 is the modern version of the 1117.

Does this help to answer your questions?

Power management

Power management forum

LM1117: Output capacitor