Please let me know about three point below of LM340's safe area protection.
①Safe area protection circuit is R17, D2, Q14,etc by Datasheet page 10, is it correct?
②In the case of reverse current, I think that a current path is below route, is it correct?
（Datasheet page 10）
Vout → R16 → R14 → D2 → R17 → Vin
③Is there information of D2's maximum rating?
Best regards,
Satoshi
HI Satoshi,
The components you mentioned are associated with safe operating area. The circuitry referred to as "SOA" is for the peak current limit. The zener breakdown voltage defines the peak of the curve.
Since this device was designed long time ago. I doubt if anyone would know the exact rating for zener D2 diode withint design reverse engineering. What we can say for sure is that it’s sufficient for the ensured operating range.
I believe that the D2 ~zener~ is a generic 1x NPN in EBO configuration, with typical breakdown around 6.5V +/-0.3V. But I could be wrong.
Hope this helps.
