SLVAET3 October   2021 TPS8802

 

  1.   Trademarks
  2. 1Introduction
  3. 2System Architecture
    1. 2.1 Battery Voltage
    2. 2.2 VCC Supply
      1. 2.2.1 Connecting VCC to VBST
      2. 2.2.2 Connecting VCC to VBAT Through a Switch
    3. 2.3 MCU Supply
      1. 2.3.1 MCU Connected to VBAT
      2. 2.3.2 MCU Connected to MCU LDO
      3. 2.3.3 MCU with VCC Connected to VBAT Through a Switch
    4. 2.4 Photoelectric Smoke Sensor LED Supply
      1. 2.4.1 LED Connected to VBAT
      2. 2.4.2 LED Connected to PLDO
      3. 2.4.3 LED Connected to LEDLDO
    5. 2.5 Example Schematics
      1. 2.5.1 Smoke and CO Schematics
      2. 2.5.2 Smoke-Only Schematics
  4. 3Current Consumption
    1. 3.1 Standby Current
      1. 3.1.1 TPS8802 Standby Current
      2. 3.1.2 Microcontroller Standby Current
    2. 3.2 Measurement Current
      1. 3.2.1 Smoke Measurement Current
      2. 3.2.2 CO Measurement Current
      3. 3.2.3 Battery Test Current
      4. 3.2.4 User Alarm Test Current
    3. 3.3 Other Current Consumption
      1. 3.3.1 Boost Charge Current
      2. 3.3.2 Initialization Current
  5. 4System Power Calculation and Measurements
    1. 4.1 Power Calculation Spreadsheet
      1. 4.1.1 Power Consumption Overview Page
      2. 4.1.2 Detailed Calculation Pages
    2. 4.2 Power Consumption Measurements
      1. 4.2.1 Power Measurement Method
      2. 4.2.2 Smoke and CO System Measurements
      3. 4.2.3 Smoke-Only System Measurements
  6. 5Summary
  7. 6References

4.1.2 Detailed Calculation Pages

GUID-20200904-CA0I-NW0K-VBG0-6SNSW6Q9ZTZQ-low.gif Figure 4-3 System Specifications Table

GUID-20200904-CA0I-97QJ-CJV3-SG1FZFJKSGSV-low.gif Figure 4-4 Smoke and CO Measurement Subroutine Timing Table

Detailed calculations are made using system specifications and subroutine timing. The system specifications are mostly based on component parameters: TPS8802 block current consumption, MCU current consumption, Schottky diode leakage, etc. The subroutine timing is the sequence of microcontroller events required to perform a smoke measurement, battery test, or user alarm test. Each line in the subroutine timing represents a microcontroller event with its associated delays between events. The measurement timing table is linked to the power calculation to calculate how much average current each block in the subroutine uses. Summing each block’s current calculates the average current consumption for a subroutine, and summing all of the subroutines calculates the average system current.

GUID-20200904-CA0I-D3VW-7W6M-WNBJRCVLLTW8-low.gif Figure 4-5 Detailed Power Calculation