STUSB4500: Understanding the typical application schematic

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Abbas_BrainAlive

Joined Feb 21, 2018
99
Hello.

I have been studying USB-PD lately, and I came across a USB-PD controller from ST, the STUSB4500. This is the typical application circuitry, as per the datasheet:
STUSB4500.png

There are a few things I am unable to understand in this schematic:
1. What is the purpose of R1, R4, C4 and D4?
As per the datasheet, a current limiting resistor is required in series with the VBUS_VS_DISCH pin. R1 or R4 either can serve this purpose (both the values suit well for the purpose, as specified in the datasheet). What are the other 3 components doing?
2. In the biasing circuitries of the power MOSFETs (along the dark-red line), what is the purpose of 22K, 100E resistors and 100nF capacitor?
In the biasing circuitries, the 100K resistor sufficiently biases the MOSFETs, giving them a default state. But what are the other three components doing?

Please note that all the signals going to MOSFETs are Open-Drain.

I would be grateful if someone could explain the purpose of these auxiliary components.
 
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