# Confusion over SMPS controllers/regulators

I am looking at datasheets for ICs like FAN4800 or NCP1337. Some of these are PFC boost converters and others are for other types of SMPS topologies.

My confusion is that I can't tell if these ICs are actually supposed to be regulating the output voltage. There is never any mention of PID or compensation techniques to use with these ICs. I am hoping that its all included internally, but I see no hints of a PID system when I look at the internal block diagrams of these parts. Is this correct to assume or do I need to design an external compensation circuit?

On the PFC side, $V_{FB}$ is the voltage feedback input, and you can see its external compensation on the $V_{EAO}$ pin. Also, $I_{SENSE}$ is the current feedback input, and you can see its external compensation between $V_{REF}$ and $I_{EAO}$.
On the PWM side, $V_{DC}$ is the voltage feedback, and the compensation is on the secondary side around the TL431A 'error amplifier'.