TIDUF26 june   2023 BQ24072 , LMR36520 , TLV62568 , TPS2116

 

  1.   1
  2.   Description
  3.   Resources
  4.   Features
  5.   Applications
  6.   6
  7. 1System Description
    1. 1.1 Key System Specifications
  8. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Design Considerations
      1. 2.2.1 24 VAC to DC Rectification
      2. 2.2.2 eFuse Protection
      3. 2.2.3 5-V Rails
        1. 2.2.3.1 LMR36520 Voltage Rail
        2. 2.2.3.2 USB Power Input
      4. 2.2.4 Power Source ORing
      5. 2.2.5 Battery Management
      6. 2.2.6 3.3-V Power Rail
      7. 2.2.7 Power Rail Current Sensing
      8. 2.2.8 Backlight LED Driver
      9. 2.2.9 BoosterPack Overview
    3. 2.3 Highlighted Products
      1. 2.3.1 LMR36520
      2. 2.3.2 TPS2116
      3. 2.3.3 TLV62568
      4. 2.3.4 INA2180
      5. 2.3.5 TPS92360
      6. 2.3.6 TPS2640
      7. 2.3.7 BQ24072
  9. 3Hardware, Software, Testing Requirements, and Test Results
    1. 3.1 Hardware Requirements
    2. 3.2 Test Setup
    3. 3.3 Test Results
      1. 3.3.1  24-VAC Start-Up and Shutdown
      2. 3.3.2  USB Start-Up and Shutdown
      3. 3.3.3  ORing
      4. 3.3.4  LMR36520
      5. 3.3.5  TLV62568 Transient Response
      6. 3.3.6  BM24072 Transient Response
      7. 3.3.7  TLV62568 (3V3 Power Rail)
      8. 3.3.8  LMR36520 (LMOut Power Rail)
      9. 3.3.9  BM24072 (BMOut Power Rail)
      10. 3.3.10 Reference
        1. 3.3.10.1 TLV62568
        2. 3.3.10.2 LMR36520
  10. 4Design and Documentation Support
    1. 4.1 Design Files
      1. 4.1.1 Schematics
      2. 4.1.2 BOM
    2. 4.2 Tools and Software
    3. 4.3 Documentation Support
    4. 4.4 Support Resources
    5. 4.5 Trademarks
  11. 5About the Author

2.2.2 eFuse Protection

The TIDA-010932 reference design leverages a TPS26400 eFuse to protect the ICs in the event of an overvoltage or overcurrent event. The load, source, and device protection are provided with many adjustable features including overcurrent, output slew rate, and overvoltage, undervoltage thresholds. The internal robust protection control blocks along with the high voltage rating of the TPS26400 helps to simplify the system designs for protection. Figure 2-4 shows the implementation of the TPS26400 in this reference design.

GUID-20230530-SS0I-FRNW-58QB-XT5HRJFLRXX3-low.png Figure 2-4 TPS2660 E-Fuse Implementation

To program the current limit threshold for the board, use Equation 2 to calculate the required resistance.

Equation 2. R ( I L I M ) = 12 I L I M

Using the 2 A as the current limit, a resistance of 6 kΩ is calculated. Rounding to the nearest 1% resistor value results with a resistance of 5.36 kΩ.

For the UVLO and OVLO set points, Equation 3 and Equation 4 are used to calculate the required resistance values. For minimizing the input current drawn from the power supply {I(R9,10,24) = V(IN) / (R9 + R10 + R24 )}, use higher value resistance for R9, R10, and R24 . However, the leakage current due to external active components connected at resistor string can add error to these calculations. So, the resistor string current, I(R9,10,24) must be chosen to be 20 × greater than the leakage current of the UVLO and OVP pins.

From the device electrical specifications, V(OVPR) = 1.19 V and V(UVLOR) = 1.19 V. From the design requirements, V(OV) is 36 V and V(UV) is 10 V. To solve the equation, first choose the value of R24 = 30.1 kΩ and use Equation 3 to solve for (R9 + R10) = 880.5 kΩ. Use Equation 4 and a value of (R9 + R10) to solve for R10 = 80 kΩ and finally R9 = 825 kΩ. Choose the closest standard 1% resistor values: R9 = 825 kΩ, R10 = 80 kΩ, and R24 = 30.1 kΩ.

Equation 3. V O V P R = R 3 R 1 + R 2 + R 3 × V O V
Equation 4. V U V L O R = R 2 + R 3 R 1 + R 2 + R 3 × V U V

J6 provides the option to change the mode for the eFuse based on the needs of the designer. The mode can be switched from current limiting with auto-retry, current limiting with latch off, and circuit breaker with auto-retry, and is based on whether the mode pin is connected to RTN, connected to the 402-kΩ resistor to RTN, or left open respectively.