[sdiy] LDO regulators and ceramic caps

[Richie Burnett]

Hi all,

Out of interest how are you guys and girls dealing with the issue of LDO 
regulator stability with ceramic capacitors?  The datasheets for most modern 
micro's and op-amps preach about the importance of low-ESR 0.1uF ceramic 
decoupling caps across the power pins of the device.  But the LDO regulator 
datasheets say that low-ESR ceramics across the output will make the 
regulator go unstable and are a no no.

Just wondering how people are resolving this issue.  My board is quite small 
2"x2" so it's unlikely that track lengths would add enough resistance to the 
ceramic capacitors to move them into the stable region for the LDO 
regulator.

I've seen at least one commercial solution that had 100 ohm resistors in 
series with everything fed from the LDO output to isolate the decoupling 
caps from the regulator, but then that series resistance wrecks the 
regulation!

-Richie,