RHFL7913A negative LDO regulator current limit adjustment

[mijuhi]

Hi,

I have a problem of adjusting the RHFL7913A negative LDO regulator current limit to about 0.5A by a Rsh resistor. I tried with 12.4 kOhm but no current limitation is seen even at around 910 mA load. Anyone happen to know the correct resistance value?

Thank you.

-Mijuhi

 

[AScha.3]

you connect 12k from I(limit input) to Vin (-) ? nothing limit ?

then take other chip, thats better for you... what current you need ? and what output voltage ?

ie. ADP7182ACPZ would limit at about 350mA . (mouser has it)

 

[mijuhi]

Thank you for the comments. Yes, it was connected like you described. Unfortunately cannot use COTS parts, we have Class I space project and only QML-V qualified parts are accepted. And parts are actually already ordered due to long lead time.

[AScha.3]

ok - so : what output voltage ?  what is input voltage?

[mijuhi]

Output voltage is either -4.5V or -3.3V from about -5V (multiple regulators). 

[AScha.3]

ok, so from ds i assume: current limit is set by taking away some current from internal current source -> I

so guessing its 2mA (no value in ds i found) , at -5v you could try (5/2) 2k5 to stop it, so i recommend: use a small pot 10k and try...or just try 5k, 4k, 3k resistors.

[mijuhi]

You are probably right. For the positive regulator RHFL4913A there is a graph which defines the resistance value (DS3625 Rev. 21 figure 45) and I assumed that internally there is no difference between these two parts (unfortunately, we do not use RHFL4913A parts). As you suggested, I will try with different R values. Thank you for fast replies!