TIDUEO0C July   2019  – March 2021

 

  1.   Description
  2.   Resources
  3.   Features
  4.   Applications
  5.   5
  6. 1System Description
    1. 1.1 Key System Specifications
  7. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Design Considerations
    3. 2.3 Highlighted Products
      1. 2.3.1 TPS63900: 1.8V-5.5 VIN Buck-Boost Converter With 75-nA Ultra-low Quiescent Current and 400-mA Output Current
      2. 2.3.2 TPS610995: 0.7 VIN Synchronous Boost Converter With 400-nA Ultra-low Quiescent Current and 1-A Peak Current
      3. 2.3.3 TPS62840: 750-mA Synchronous Step-Down Converter With Ultra-low Quiescent Current Consumption
    4. 2.4 System Design Theory
      1. 2.4.1 Battery Gauge BQ35100
      2. 2.4.2 In-System Current Monitoring
        1. 2.4.2.1 Resistor Values Calculation for the two Current Ranges
        2. 2.4.2.2 LPV521 Gain Calculation
        3. 2.4.2.3 Current Ranges Simulation With TINA-TI
        4. 2.4.2.4 Key ADS7142 Register Settings in TIDA-01546 Firmware
          1. 2.4.2.4.1 ADS7142 Sampling Rate
      3. 2.4.3 NB-IoT Module From u-blox
      4. 2.4.4 NB-IoT Module From Quectel
  8. 3Hardware, Software, Testing Requirements, and Test Results
    1. 3.1 Required Hardware
      1. 3.1.1 Testing TIDA-010053
      2. 3.1.2 TPS62840 Subsystem
      3. 3.1.3 TPS610995 Subsystem
      4. 3.1.4 Software
    2. 3.2 Testing and Results
      1. 3.2.1 Test Setup
      2. 3.2.2 Test Results
        1. 3.2.2.1 Test Results With the TPS62840 Buck Converter
        2. 3.2.2.2 Test Results With the TPS610995 Boost Converter
        3. 3.2.2.3 Test Results With the TPS63900 Buck-Boost Converter NB
        4. 3.2.2.4 Summary
  9. 4Design Files
    1. 4.1 Schematics
    2. 4.2 Bill of Materials
    3. 4.3 PCB Layout Recommendations
      1. 4.3.1 Layout Prints
    4. 4.4 Altium Project
    5. 4.5 Gerber Files
    6. 4.6 Assembly Drawings
  10. 5Software Files
  11. 6Related Documentation
    1. 6.1 Trademarks
  12. 7Terminology
  13. 8About the Author
  14. 9Revision History

2.4.2.2 LPV521 Gain Calculation

The resistors R25 and R28 in the TIDA-01546 reference design are used to set the gain value of the LPV521 device:

Equation 2. GUID-D091B77C-E0AC-4E11-8CFB-B766E5F8847D-low.gif

The AVDD voltage of the ADS7142 device defines the full-scale input range of the device and for the TIDA-01546 design, it is set to 3.3 V and is the maximum input voltage. With this, and knowing the gain G, calculate the maximum VIN value for the input voltage of the LPV521 device:

Equation 3. GUID-00082DA9-49A3-4373-B09F-178C5DB0B716-low.gif

The 69 mV represents the full-scale voltage which can be applied to the input of the LPV521 device regardless of the current range used.

For these two current ranges, the maximum current value is one of the following:

  1. 69 mV / R32 = 6800 Ω =
  2. 10.47 µA for the low-current range
  3. 69 mV / 0.145 Ω = 475.86 mA for the high-current range

The minimal current values are enumerated in the following, since there are 4096 ADC steps:

  1. 10.47 µA / 4096 = 2.55 nA
  2. 475.86 mA / 4096 = 116 µA

The LPV521 and ADS7142 devices monitor the system current continuously with a minimum power consumption, since both devices draw about 1 µA when running from a 3.3-V supply.