The datasheet calls this a Hysteretic PFET Buck Controller. I had to look up “hysteretic” and even knowing it was related to hysteresis I still don’t fully grasp what it means?! Whilst I am discussing technical english – ‘buck’ controller means voltage step-down (vs. Boost = step-up) where does buck come from? I have always wondered why not just use step-down?
The National Semiconductor LM3485 was designed in 2001 and is a 1.7mm x 1.7mm die fabricated with a 2 metal analog process
The PMOS driver is the large structure at the top of the die (Either the one on the left or in the middle 🙂 ) There are a ton of different transistor structures, many of them look like Bipolar transistors, but to confirm one would need to remove the metals and stain the junctions or use scanning capacitance to resolve the junction types (Neither of which I can do.) In this image I can count four different transistor types (I think circular emitter NPN and PNPs, and rectangular NPN, and PNP) – I do not know why they chose to use all these types.