2023-10-02 11:26 PM
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
2023-10-03 12:21 AM
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)
2023-10-03 12:34 AM
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.
2023-10-03 01:16 AM
ok - so : what output voltage ? what is input voltage?
2023-10-03 03:18 AM
Output voltage is either -4.5V or -3.3V from about -5V (multiple regulators).
2023-10-03 03:39 AM
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.
2023-10-03 03:52 AM
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!