I still don't really understand what you want to do.
Maybe something like this.
(Note that I removed the pointer part of the typedef since it's generally a bad idea to hide a pointer (unless perhaps it's opaque), and I also got rid of the globals.)
Code:
#include <stdio.h>
#include <inttypes.h>
typedef struct {
uint16_t Vbias;
uint16_t SiPMCurrent;
uint16_t LEDCurrent[2];
} t_SenseDataRaw;
void voltage(t_SenseDataRaw *k, float *adv) {
adv[0] = k->Vbias;
adv[1] = k->SiPMCurrent;
adv[2] = k->LEDCurrent[0];
adv[3] = k->LEDCurrent[1];
for (int i = 0; i < 4; i++)
adv[i] = adv[i] * 3.3 / 4096;
}
int main() {
t_SenseDataRaw SensorData;
SensorData.Vbias = 1;
SensorData.SiPMCurrent = 2;
SensorData.LEDCurrent[0] = 3;
SensorData.LEDCurrent[1] = 4;
float ADValues[4];
voltage(&SensorData, ADValues);
for (int i = 0; i < 4; i++)
printf("%f\n", ADValues[i]);
return 0;
}