LM2931CT weird behaviour

[richwalters]

Hi there.........query.....the LM2931 adj lo drop out reggie .....I notice these chips draw a massive amount of IN current (eg. 80mA... far higher than the load in my case) before zener voltage is reached then it drops way down. This isn't mentioned in the app note.
The bog standard 78 series npn configs don't have this curiousity.................Is there any way of avoiding the initial current draw with the LM2931 ?

richj

[HDTVman]

Originally posted by richwalters
Hi there.........query.....the LM2931 adj lo drop out reggie .....I notice these chips draw a massive amount of IN current (eg. 80mA... far higher than the load in my case) before zener voltage is reached then it drops way down. This isn't mentioned in the app note.

Look at the data sheet. That family of low drop-out linear regs. do have that shown as a function of input voltage.

BZ

[richwalters]

Many thanks for reply.......by chance I also got a flag from the NSemi site ...by chance the same query came up ....Quote < as an undesirable characteristic >. The LP2951 would be a better bet.

richj