I need to select a LDO with output voltage of 12V for my design.My load requirement is 1.2A,only for 2ms.So I have chosen MIC29151-12WU regulator which is capable of delivering 1.5A of load current. Since my load consumes 1.2 A only for short duration,I am thinking to use an low load current LDO with output bulk capacitance to meet the design requirement.This brings down my cost of LDO.But I am not sure about the pitfalls.Could someone advice me on this?
What limits the maximum output current of an LDO ?
1) The LDO itself limits the current because it exceeds a certain value
2)the LDO gets too hot and limits it's output current and voltage to reduce power dissipation
Depending on the LDO you choose I expect 1) to be an issue as 2 ms is enough time for most LDOs to respond. 2) is probably not an issue depending on how often you draw this 2ms pulse. If you draw a pulse every second or less, no problem. If you do this more often then dissipation can be an issue.
A solution could be to use a large capacitor at the output of the LDO, it will then supply the current. The LDO might not like this though so check it's datasheet. But probably the the large capacitor will increase cost more than using a 1.2 A capable LDO.
The safest option is just to use an LDO which can handle the current.