EFuse Calculations

Owned by Dante Sivo (RIT Student)
Last updated: Feb 11, 2023
1 min read

GOAL:

To establish an EFuse to protection the Radio Module from shorts and over current draws

PARAMETERS:

Design Ideas:

  • Copy Sensor Modules solution
    • TBD
  • TPS2552/TPS2553
    • Adjustable EFuse by TI
      • Fuse limit between 0.075A to 1.7A
      • Vin between 2.5V to 6.5V
      • Typically used in USB charging devices
      • 6 pin, easily to solder package. 
      • Available on JLCPCB
      • Relatively cheap (<$5 per)
        • We can save more money by using a WSON package
    • Differences between the two TPS IC's
      • TPS2552 - Active Enable Low
      • TPS2553 - Active Enable High
    • Current Application Schematic Reference

Auto-retry (TPS2553)

  • During over current condition, FAULT pulls low, discharging the capacitor
  • C_RETRY begins to charge
  • Once V_EN reaches the threshold voltage to turn on, it will retry


  • RC charging equation
    • V = Vo * (1-e^(-t/RC))
      • V_EN threshold (0.66v - 1.1v)
    • Example:
      • CL= 1uF, RL = 100 Ohm
      • t_on >> ~1ms


  • Proposed RC network
    • R_FAULT = 100k, C_RET = 1uF
    • To reach the average threshold voltage
    • 0.3225 seconds
      • aka, 322.5ms

<Excel Sheet for calculating RLim>