SLAAEI3 February   2024 MSPM0C1103 , MSPM0C1104 , MSPM0G1105 , MSPM0G1106 , MSPM0G1107 , MSPM0G1505 , MSPM0G1506 , MSPM0G1507 , MSPM0G3105 , MSPM0G3105-Q1 , MSPM0G3106 , MSPM0G3106-Q1 , MSPM0G3107 , MSPM0G3107-Q1 , MSPM0G3505 , MSPM0G3505-Q1 , MSPM0G3506 , MSPM0G3506-Q1 , MSPM0G3507 , MSPM0G3507-Q1 , MSPM0L1105 , MSPM0L1106 , MSPM0L1228 , MSPM0L1228-Q1 , MSPM0L1303 , MSPM0L1304 , MSPM0L1304-Q1 , MSPM0L1305 , MSPM0L1305-Q1 , MSPM0L1306 , MSPM0L1306-Q1 , MSPM0L1343 , MSPM0L1344 , MSPM0L1345 , MSPM0L1346 , MSPM0L2228 , MSPM0L2228-Q1

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Relationship Between I, C and t
  5. 2Application Scenarios
  6. 3Derivation of Formulas
  7. 4Experimental Verification
    1. 4.1 Test Environment Setup
    2. 4.2 The Result of Experiment
  8. 5Notes

3 Derivation of Formulas

First of all, the premise of the formula is that the operating current of the MCU is consistent at different operating voltages. So the operating current at different voltages was tested. The starting voltage was 3.3V, and the supply voltage was gradually reduced, during which the change in operating current was measured by the ammeter connected in series between the power supply and the MCU. Here comes the result. Figure 3-1 shows that the current remains the same while MCU is working normally (VCC is greater than 1.6V). Besides, the device operates in run0, sleep0, and stop0 modes with currents of 1.55mA, 0.93mA, and 0.32mA, respectively, which conform to the device-specific data sheet specifications.

GUID-DF38CB6C-8305-4D2A-BC5B-F3CC49E3D6DA-low.jpg Figure 3-1 Diagram of the Operating Current of the MCU vs. Supply Voltage

Based on constant current, the MCU maintains the required energy for:

Equation 2. E = 0.5 × I t × V work + V cutoff

And from a capacitance point of view, the reduced energy can be expressed as:

Equation 3. E = 0.5 × C × V work 2 - V cutoff 2

The energy of the capacitor is used to supply the normal operation of the MCU, so Equation 2 and Equation 3 can be connected to further obtain the equipment operating maintenance time t which is expressed as Equation 2.