These circuits date back to the late ‘90s (below). There are plenty of SMT LDOs with soft start features but I’m not seeing anything in TO-220. I am angling towards using the MIC29152 or MIC2941A for 6V / 750mA, which encompasses two 6922 heaters and some 5V relays running at 4.3V downstream. I’m looking to avoid heavy inrush current. I’m not trying to ramp power over a long interval - even 1 second is more than enough.
In my application power will already be applied, and I am thinking of having a simple SPST “On” switch that toggles the EN pin from ground to open (with the R4/C1 node connected regardless). Is there a snazzier way to accomplish A) the soft start, and B) the turn on, or should I just copy what’s drawn in the ancient Micrel white paper (with R1/R2 corrected of course)? The TI version is almost the same but for an added cap across the upper R in the ADJ network, and the designer assumes an enable voltage separate from the input voltage, which is not the case in my application.
I didn’t bother including the classic LM317 soft start diagram because it has no enable pin.
Go easy on me, I’m not well versed in these circuits.
In my application power will already be applied, and I am thinking of having a simple SPST “On” switch that toggles the EN pin from ground to open (with the R4/C1 node connected regardless). Is there a snazzier way to accomplish A) the soft start, and B) the turn on, or should I just copy what’s drawn in the ancient Micrel white paper (with R1/R2 corrected of course)? The TI version is almost the same but for an added cap across the upper R in the ADJ network, and the designer assumes an enable voltage separate from the input voltage, which is not the case in my application.
I didn’t bother including the classic LM317 soft start diagram because it has no enable pin.
Go easy on me, I’m not well versed in these circuits.
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