TIDUEY7 July   2021

 

  1.   Description
  2.   Resources
  3.   Features
  4.   Applications
  5.   5
  6. 1System Description
  7. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Design Considerations
      1. 2.2.1  System Control and Processing
      2. 2.2.2  Analog Front End
      3. 2.2.3  Input Voltage Monitoring: 5 V, 20 V, 40 V, and ±5 V
      4. 2.2.4  Bidirectional Current Sense: ±2 A
      5. 2.2.5  Unipolar Current Sense: 0.25 A to 1 A
      6. 2.2.6  TMP461-SP: Local and Remote Temperature Sensing
      7. 2.2.7  NTC Thermistor Temperature Sensing
      8. 2.2.8  Adjustable Voltage Source
      9. 2.2.9  Fixed Output Current Source
      10. 2.2.10 Adjustable 4-mA Current Source
      11. 2.2.11 Power Tree and Power Sequencing
    3. 2.3 Highlighted Products
      1. 2.3.1  MSP430FR5969-SP
      2. 2.3.2  ADC128S102QML-SP
      3. 2.3.3  DAC121S101QML-SP
      4. 2.3.4  LMP7704-SP
      5. 2.3.5  INA901-SP
      6. 2.3.6  LM4050QML-SP
      7. 2.3.7  LM158QML-SP
      8. 2.3.8  LM139QML-SP
      9. 2.3.9  TMP461-SP
      10. 2.3.10 TPS7A4501-SP
      11. 2.3.11 TPS7H2201-SP
  8. 3Hardware, Software, Testing Requirements, and Test Results
    1. 3.1 Required Hardware and Software
      1. 3.1.1 Hardware
      2. 3.1.2 Software
    2. 3.2 Test Setup
      1. 3.2.1 Voltage Monitor Test Setup
      2. 3.2.2 Current Monitor Test Setup
    3. 3.3 Test Results
      1. 3.3.1 Voltage Measurement - Noise Floor Results
      2. 3.3.2 Voltage Measurement - Linearity Results
      3. 3.3.3 Current Measurement - Noise Floor Results
      4. 3.3.4 Current Measurement - Linearity Results
      5. 3.3.5 Analog Outputs
  9. 4Design and Documentation Support
    1. 4.1 Design Files
      1. 4.1.1 Schematics
      2. 4.1.2 BOM
    2. 4.2 Documentation Support
    3. 4.3 Support Resources
    4. 4.4 Trademarks
  10. 5About the Author

2.2.11 Power Tree and Power Sequencing

Figure 2-11 shows the power tree consisting of four main power components: the TS7A4501-SP, LMP4050QML-SP, TPS7H2201, and boost circuit.

GUID-20210406-CA0I-RWWK-DQXC-MKLZKG9D3DNM-low.gifFigure 2-11 Power Tree and Sequencing

The TPS7A4501-SP is selected to power these rails because of its low noise output to ensure no performance degradation due to injected power noise. There are three TPS7A4501-SP used to power this design. The first TPS7A4501-SP provides a 3.3-V rail used to power the MSP430FR5969-SP. The second TPS7A4501-SP is used to provide the 3.3-V digital voltage rail for the ADC128S102QML-SP. The third device is used to regulate the output of the discrete boost controller to 12 V. The 12 V supplied by the TPS7A4501-SP is optional to the operation of this reference design and an external 12 V can be provided to bypass the boost and LDO circuit.

The LMP4050QML-SP are voltage references to provide a stable voltage at two places in the power tree. The first is the 5-V analog voltage rail for the ADC128S102QML-SP. The second rail is the 2.5-V reference for the integrated ADC in the MSP430FR5969-SP. It is important that this is a clean stable signal, or else it can cause inaccuracies in the measurements taken from the ADC.

The TPS7H2201-SP is a load switch that is used for sequencing and ramp up power safely for the op amps. The main power sequencing in this design is to make sure that the ADC128S102QML-SP analog voltage rail has ramped up first before the digital voltage rails ramps up as Figure 2-12 shows. It is important that the analog voltage rail of the ADC128S102QML-SP is stable at 5 V, because the digital rail must stay at least 0.3 V below the analog voltage rail or else it could cause damage to the ADC128S102QML-SP.

GUID-20210415-CA0I-PVHQ-FX98-HTJ292DF5LN0-low.pngFigure 2-12 ADC128S102-SP Start-up Power Sequence