Datasheet maximum ratings

[lawcuenca]

Hi everyone,
I am new in looking up datasheets for discrete devices (Diodes, IGBTs, MOSFETs and SCRs). I would just like to know how the manufacturers come up with the device maximum ratings?:?: Your meaningful response will be greatly appreciated.

 

[keith1200rs]

From the process characteristics rather than the design. For example, a process may have transistors which break down at 7V. That will be tested. They then design a chip to work at 5V (up to 5.5V really). Between 5.5V and 7V is a grey area. The chip wasn't designed to work there but shouldn't be damaged. Once you reach 7V there is a risk it will self destruct.

Keith

 

[lawcuenca]

Keith,
First of all, thank you for sharing about the process. Another thing, are their any formula used to determine let's say MOSFETs' maximum ID or an IGBT's maximum IC based from other datasheet parameters? Just like when we solve for the maximum power dissipation PD = (Tjmax-Tc)/RoJC ? Thanks in advance.

Law

 

[keith1200rs]

Law,

Sorry, my answer was a bit off topic. It is based on my experience designing ICs. I have not designed many with high current, and then only up to a few amps peak so I don't know the different failure modes. Some failures will happen in a short duration, others are heat based so happens slower. You can also overheat the device in a short space of time before the heat can be conducted to the package.

Hopefully someone will chip in with an answer with some more physics.

Keith

 

[lawcuenca]

Hi Keith,
Thanks for the info. Maybe I'll just read more articles regarding this topic to learn more about it.

 

[love_analog]

Doesn't datasheet specify the maximum Id itself. Why do you need to calculate it.

Remember they pulse the Id when they specify it (as far as I remember) to allow heat to dissipate.