When does this current regulator IC output 30mA?

[treez]

Hello,
We wish to use the TO220 version (three terminal) of the LR645 Current source with a 330V input.
We want the output current to be limited to 3mA by the LR645. However, on page 1 and page 2 of the datasheet it appears to suggest that LR645 can sometimes produce 30mA. We were hoping that it was limited to 3mA. Do you know when it would supply 30mA?

LR645 Datasheet:
**broken link removed**

 

[esp1]

hi treez,
I think you are misreading the d/s it states 3mA thru 30mA is possible, depending upon the current sense resistor values.

E

 

[treez]

sorry but there are no current sense resistors associated with it...(I think you mean the resistive divider which adjusts vout on the 8 pin version, but that isn't the subject of the question)

 

[esp1]

hi fedz,
I will relook at the d/s, the way I read it is the 3mA to 30mA can be set, get back to you.
E

 

[treez]

actually..thanks you are right, it is a voltage regulator , not a current regulator. I misinterpreted the top line of the datasheet..

The Supertex LR645 is a high input voltage, low output
current linear regulator.

I read the above as....

The Supertex LR645 is a high input voltage, low output,
"current linear regulator".

It would have been nice if it regulated vout to 10v and regulated current to 3mA maximum, ah well

 

[esp1]

hi,
For a 10V at 3mA, that's a sink load of ~3k3.

You could easily build a 3mA CC, using a JFET.? eg: this LTS image

E