These are both 3.3v regs, they have the same package, they appear to have nearly identical specs, yet the first one is rated for 250mA and $1.50, and the second is rated for 150mA, and $0.50:

http://www.ti.com/lit/ds/symlink/lp2992.pdf http://www.ti.com/lit/ds/symlink/lp2985-18.pdfThe first one seems to have a slightly lower dropout. 350mV @ 125 degrees, versus 400mV @ 125 degrees for the second.

But the second one has a 150 degrees max junction temperature, while the first has only a 125 degrees max junction temperature, and I know this is used in the power dissipation calculations.

They both can handle up to 16v, and both list their PEAK output current as 350mA.

So what's the difference? Is it the dropout voltage? If so, where does that factor into any power dissipation calculations? I looked up how to calculate the power dissipation, and found this equation:

PD = IOUT * (VIN - VOUT) + VIN*IQ

where VIN = input voltage; VOUT = output voltage; IOUT = output current, A; and IQ = quiescent current, A

I assume quiescent current is also known as ground current as that seems to match up with the minumum quiescent current listed in the absolute maximum ratings and there's no other quiescent current listed. In which case for both vregs, it's 850uA typical at 150mA output. Which means as far as the power dissipation equation goes, the two regulators are identical.

So why is the current rating so different for these parts?