Parsing the Supertex LR8N3 HV regulator

[jackinnj]

A long while back someone contacted me regarding the stability of the LR8N3 regulator. I'm going to post some of the results of putting it through its paces.

 

[jackinnj]

I put up the wrong file before: Here's the PSRR with and without bypass (10uF) on the adjust pin:

[IMGDEAD]http://www.tech-diy.com/RegPowerSupplies/SuperTex/SupertexLR8_PSRR_Bypassed2.gif[/IMGDEAD]

and a bode plot. Solid red line is adj pin bypassed with 10u. At the zero gain crossing there appears to be 57 deg phase margin:

[IMGDEAD]http://www.tech-diy.com/RegPowerSupplies/SuperTex/SupertexLR8_Bode.gif[/IMGDEAD]

 

[winhill2]

The Bode plot is what, from the unregulated HV input to the output? From the ADJ-pin network ground pin to the output?

Given that so many folks add outboard pass transistors to the LR8, using it merely as a control element, what would be the best LR8 Bode plot info to use in analyzing the loop stability and output-impedance reactive properties in that situation?

Thanks!