SLYU056 June 2020 TMAG5123 , TMAG5123-Q1
R1 functions as a pullup resistor for the open-drain output of the TMAG5123.
R2 is a current-limiting resistor to control the output intensity of the signal diode D1.
While not normally populated, C3 is an optional SMT pad for capacitor placement, forming a first-order low pass filter with the pullup resistor.