How to calculate the total power consumption of Si1153? What are the major factors that impact power consumption?
A detailed power consumption breakdown of Si1153 is covered in Section 6 of the application note AN950:
There're a total of 4 current consumption values used in the equation:
1. Standby Current: 1.25uA (Vdd = 3.3V)
2. Active Current (internal controller processing): 4.5mA (Vdd = 3.3V)
3. ADC Current (suspend mode): 0.525mA (Vdd = 3.3V)
4. LED Current: set by the host
Since the standby current is relatively small comparing to the rest, we can ignore that to simplify the estimation.
I = I_internal_controller + (I_adc_setup + I_adc_active) + I_led
The integration time of the ADC is controlled by the HW_GAIN setting. The default integration time is 24.4us and 24.4*2^HW_GAIN if HW_GAIN is set to non-zero values.
The internal controller processing time per measurement is 155us. The ADC setup time is 48.8us. The si1153 sensor will perform 2 back-to-back measurements, one with the LED on and the other with the LED off. Therefore, if we assume integration time is set to default and LED current is set to maximum 354mA, the total power consumption will be:
I = (155us * 4.5mA + 48.8us * 525uA + 2* 24.4us * 525uA + 24.4us * 354mA) * Fs
where Fs is the sampling frequency of the measurement.