LD1117 could be unstable with selected capacitors

[nuess0r]

@mschwingen did a schematic review and one issue was:

The LD1117 datasheet does not make any notes about stability. Similar
LDOs from other vendors (LM1117 etc.) are known to become unstable with
low-esr (ceramic) output capacitors, so I would guess the LD1117 to
behave similarly. C3 (0805 ceramic) may have a too-low ESR for stable
operation - a 10uF electrolytic or tantalum might be a better choice (or
a LDO that is specified for ceramic output caps - I have used XC6206P33
in other projects, but here are lots of alternatives in SOT-23 available).

[nuess0r]

Good catch!

According to the AS1117 datasheet (which is the one available as basic part at JLCPCB) an 22 µF tantalum capacitor is recommended to guarantee stability (I have 4.7 µF ceramic).
Also I found the problem that I don't fulfill the minimum load requirement (10 mA) to guarantee voltage regulation when all LEDs are off.

I replaced the LDO now with the XC6206P33PR (SOT-89). The SOT-23 variant should be able to handle the expected heat dissipation but I go for the SOT-89 for more robustness (even if it is a extended part at JLCPCB).

As basic part alternative there is the HT7533-1 but there I found no information in the datasheet about stability and recommended capacitor type. Only that the typical application is with 10 µF. So if someone wants to try, go for it.