JAJU299A June   2017  – January 2023

 

  1.   概要
  2.   リソース
  3.   特長
  4.   アプリケーション
  5.   5
  6. 1System Description
    1. 1.1 Key System Specifications
  7. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Highlighted Products
      1. 2.2.1 TPS82130
    3. 2.3 Design Considerations
      1. 2.3.1 Inverting Buck-Boost Topology Concept
      2. 2.3.2 VIN and VOUT Range
      3. 2.3.3 Maximum Output Current
        1. 2.3.3.1 Thermal Limits
        2. 2.3.3.2 Stability Limits and Output Capacitor Selection
      4. 2.3.4 Design Precautions
      5. 2.3.5 Enable Pin Configuration
      6. 2.3.6 Power Good Pin Configuration
      7. 2.3.7 Discharging Output Voltage
      8. 2.3.8 Adjustable Soft-Start Time
      9. 2.3.9 Input Capacitor Selection
  8. 3Getting Started Hardware
  9. 4Testing and Results
  10. 5Design Files
    1. 5.1 Schematics
    2. 5.2 Bill of Materials
    3. 5.3 PCB Layout Recommendations
      1. 5.3.1 Layout Prints
    4. 5.4 Gerber Files
    5. 5.5 Assembly Drawings
  11. 6Related Documentation
  12. 7Trademarks
  13. 8Revision History

2.3.3.1 Thermal Limits

The primary maximum output current limitation in most designs is a thermal limitation. As the output current increases, the absolute power loss (in mW) in the TPS82130 also increases, which causes a higher temperature rise across the thermal impedance of the TPS82130 device.

The TPS82130 data sheet recommends operating below a device temperature of 110°C and forbids operating above 125°C for reliability. Therefore, Figure 4-1 contains two thermal limit lines: one for a 110°C and one for a 125°C operating temperature. These lines are calculated by multiplying the power loss of the TPS82130 from Figure 4-2 by the θJA of the TPS82130EVM-720, which is provided in the device data sheet as 46.1°C/W, and adding this value to a 25°C ambient temperature.

Using this method, the maximum output current at any ambient temperature can be calculated. Simply subtract the maximum ambient temperature from either 110°C or 125°C to obtain the allowable temperature rise. Divide the θJA of the printed circuit board (PCB) by this temperature rise to obtain the allowable power loss. Find this power loss in Figure 4-2 to determine the maximum output current under specific conditions. 46.1°C/W is useful as an estimate of θJA. See Equation 5 for the calculation.

Equation 5. GUID-D64BC3A2-66E8-4BD2-B679-E19448303EF1-low.gif