and I think that it looks like an AND gate. Hopefully I will be corrected if I have identified the gate incorrectly. The gate connected to the LIN I think I have identified as a NOT gate. Hopefully I will be corrected if I have misidentified the gate. I think I understand that the LIN takes a high signal or a low signal (high = logic 1 and low = logic 0) so if that is so then the output of the NOT gate will be 0 when LIN is high and 1 when LIN is low.
The gate most directly connected to the VCC is a little bit more mysterious to me right now in its functioning. With the functioning of the NOT connected to LIN things are clear since there is a designated high and low signal that represent clearly a logic one or logic zero. If I understand correctly the VCC is a power source which could potentially be something like a flow of electrons from a 12V solar panel. Is that correct?
Right now I am trying to get an understanding of what is happening here when LIN is high:
As for the other questions … hmmm … give me a day to find the best verbiage. But it’s a non-real, but functional, depiction of an AND gate w/an inverting input or a NAND gate with the same. In either case the functional device has complementary outputs. When one is a logic HIGH, the other output is a logic LOW … and vice-versa.
The UV DETECT block is an undervoltage detector (ie, it outputs 1 when Vcc is too low. It has two outputs, one that goes to the PULSE GEN block, and one that feeds the logic that drives the LO output thru the FETS.
On logic, the bubble (round circle) is a shorthand way of indicating an inverter. So that gate inverts the output of UV_DETECT and ANDs it with the output of DELAY. So the AND gate is a 1 if LIN is high AND UV_DETECT is LOW (ie, Vcc is high enough).
On the output side, it has complementary outputs. When the top one is hi, the bottom is low, and vice-versa. These drive the output FETs. You only want one of those two FETs on at a time since if they would both be on, they would short Vcc to COM. In reality, there’s probably a bit of dead time built into the gate so there’s a brief time when both are off as they are switching. The two N-FETs are there to provide suitable drive to the LO output.
You are right that the HIN and LIN inputs pass thru inverters. SD passes thru a non-inverting buffer. The symbol inside the triangle shows that these are Schmitt inputs and have a bit of hysteresis. That feature helps clean up some potential noise on the inputs. The pulldown resistors on the inputs are there so they are at a defined value (logic 0) if nothing’s hooked up to them, or if whatever is driving them (say the outputs of a microprocessor, just after reset) hasn’t yet been configured yet.