# Safe Operating Area

This is my LDO. 3A part.

• Input is 12V
• Output is 5V.

As per Figure 2-41 on page 15, at 85degC, I am limited to 0.2A of max load current.

How can I get the 2A load current with the Vin-Vout of 7V?

If I calculate the Tj of device at this condition, it is = (14*56)+85 = 869degC. That's not within the limits.

I'm actually using a TO-263 package, but I have taken values of 56 thermal resistance for the TO-252 package which is a close one.

Even if 2A load at Vin-Vout=7V is OK from the SOA graph, my Tj is very high. The device is not actually safe, right? What is wrong in my understanding?

If you look at the bottom axis of that chart you see that at a $$\V_{in}-V_{out}\$$ of 7 V and $$\T_A\$$ of $$\85^\circ C\$$ the current is around 1/4 A, so a 2 A load at that voltage is not okay by the SOA graph. Figure 2-42 shows pretty much the same thing. If you want to get 2 A out of it you'd need to reduce the input voltage or maybe heat sink it enough to keep it in the SOA, but that might not be possible. When you look at an SOA chart you want to stay at that horizontal part of the curve before it starts to drop. For high $$\V_{in}-V_{out}\$$ a switching regulator is generally better.