After replacing shorted cap, a new measuring attempt was taken.
First shot got a bit of contact bouncing, so it is not shown here.
The cap went down from initially 47uF to 40uF after first treatment, after second it remained at 40uF.
The results are not as expected: Vin IC peak is below max. spec of 36V and both measurements are close to each other with a bit over 34Vpeak.
At 30V with this setup no problem, but its close to max specs, so higher Vin or more lead inductance would come up to over rated spec.
What remains as a cause is the Enable Pin which is driven far above limited specs of Vin IC + 0.4V, on startup it gets 30V above Vin IC!
En is equal to Vin as in this setup they are shorted and therefore chances are high to break it independent of the applied voltage
As this device is ESD rated, it could be enough to place 10k resistor instead of short between En and Vin (ESD diode at En clamps to allowed voltage and the current is limited to well under 10mA).There is a 100k resistor between En and
GND Vin IC
, have to check the value.
Hopefully it has a high resistance value and works together with 10k...So no need to connect En Pin to anything for normal operation and dangerous to do so - my mistake.
Edit 16.9.: corrected wrong statements
Not sure if the inductance does help more or does more harm...
There are some other issues with the design of this module, so it leaves a tasteless aftertaste - as we say in german
But it was a good practice where to look for the traps in designing in this kind of linear regulators