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

2.4.3 LED Connected to LEDLDO

Any LED can be powered through the LED LDO. The LED LDO is current limited and has a series diode to block reverse current. The LED LDO is supplied by VBST and regulates to a programmable voltage between 7.5 V and 10 V, but does not require regulation in order to charge the LED supply capacitor. When the LED LDO is enabled and VBST is less than the programmed voltage, the LED LDO outputs the VBST voltage with a typical 1 V diode drop and 3 mA current limit. If VCC is connected to VBST, the LED LDO output is lower than PLDO in the pass-through mode and higher than PLDO in the regulation mode. For this reason, the LED LDO is best used when VLED(MIN) is above 4.5 V.