SLVAET3 October 2021 TPS8802
- Trademarks
- 1Introduction
- 2System Architecture
- 3Current Consumption
- 4System Power Calculation and Measurements
- 5Summary
- 6References
4.2.3 Smoke-Only System Measurements
Figure 4-12 Energia Code Excerpt for
Taking Smoke and CO MeasurementsThe smoke-only smoke measurement subroutine controls the TPS8802 and collects the data required to determine the smoke concentration in the chamber. The waveforms verify that the Energia code is correctly written.
Figure 4-13 Smoke Measurement
Waveforms in the Smoke-Only System
Figure 4-15 Multiple Smoke
Measurements Waveforms with VBAT=2.6 V
Figure 4-14 Power and Signal Waveforms
in the Smoke-Only SystemThe supply current with the LED connected and disconnected is measured at two voltages, shown in Table 4-2. Four sets of measurements are taken at each condition, making the total measurement time 40 seconds for each condition. For this calculation, the MCU standby, MCU active, battery test, and user alarm test currents are set to zero because they are not implemented in the Energia code. The measurement matches the calculation within 100 nA.
The calculation accuracy verifies that the calculation can be modified to estimate the power consumption with different system specifications. The result of the power calculation with MCU currents, battery test currents, and user alarm test currents added is shown in Figure 4-1.
| Supply Voltage | VBAT=3.0V | VBAT=2.6V | ||
| Condition | LED on | LED off | LED on | LED off |
| Measurement | 5.21 μA | 2.92 μA | 5.03 μA | 2.78 μA |
| Calculation | 5.11 μA | 2.86 μA | 5.02 μA | 2.77 μA |