I was looking at the Zynq-7000 SOC startup sequence designed in the Zynq Evaluation and Development board (ZedBoard), which requires specific voltage level regulation sequence (1.0V, 1.8V, 3.3V and 1.5V precisely). To achieve such sequence, the designers used a quad comparator LM339 to ensure the previous voltage level is properly regulated and settled before start regulating the next voltage level.
The LM339 output is a transistor which goes HIGH impedance when Vin+>Vin- and ties to REF when Vin+
Since the output is already pulled-up to 5.0V, what is the purpose of the Schottky barrier diode? (Precisely D23 and D24)
And, since the LM339 inputs are transistor, don't they require input resistors?
Datasheets of components here:
EDIT: Added datasheet for the Zynq-7000 and link to the Zedboard schematics for more info