An LM358p is a dual opamp IC which I used in a single supply configuration. I drive the LM358 just shy of its absolute maximum voltage which is +30V. So I gave I supplied 28.8V (+-0.1V). It works flawless but the power supply is a Meanwell switching supply which introduces transient when plugging into the mains supply.
The transient arise when I was plugging in the AC wire to the mains. I used an anchor 6A 3-pin male plug for connection. It was at the brief moment when the transient arise.
The transient which arises apparently has enough power that it blew the epoxy off the silicon and it did with a loud bang.
Doing rough calculation at the moment this happened
Let’s say the transient is double the supply voltage of = 2 x 28.9 V= 57.8V
let’s say the current drawn by the IC is 40mA which is its absolute maximum.
power = voltage x current = 57.8V x 40mA = 2.312W
so for a brief moment, this 2W is radiated by the silicon chip. Which caused the heating up of the epoxy and generating enough expanding force which blew out like that.
but let’s take a more reasonable transient voltage(ISO 7637-2: 2011) of approximately 110V at a rise time of 0.5uS.
so power = 110V x 40mA = 4.4W .
Leave a Reply