SLVAFR8 January   2025 TPS1685 , TPS1689 , TPS25984 , TPS25984B , TPS25985 , TPS25990

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Over-Current Response of Conventional eFuse Devices
  6. 3Challenges with Current Limit Functionality
  7. 4Proposed Design Using TI's High-Current eFuses
    1. 4.1 Steady-State Over-Current Protection in TPS25984, TPS25985, TPS25990, and TPS1685 eFuses
    2. 4.2 Design Guideline
  8. 5Thermal Performance with Continual Transient Load Current
  9. 6System Level Advantages with TI's eFuse Design
    1. 6.1 Lower Number of eFuses to be Connected in Parallel
    2. 6.2 Reduced PSU Size
  10. 7Summary
  11. 8References

6.1 Lower Number of eFuses to be Connected in Parallel

Customer Use Case:

  • VIN = 12V,
  • TDC = 220A, and
  • IMAX = 370A for 12ms (max).

Using conventional eFuses, the minimum over-current protection set point needs to be around 400A, considering a 10% margin on top of the IMAX. To support this requirement, eight (8) conventional eFuses with a continuous output current rating of 50A (without air flow) are required to be in parallel, as there is no over-current protection until the system current reaches 400A.

Using TI's eFuse design, the IOCP threshold is set at 1.1 times TDC, which becomes approximately 240A (220A x 1.1). Considering k as 0.5, ISFT is at approximately 480A. One (1) TPS25990 (with a continuous RMS current rating of 50A) and a maximum of three (3) TPS25985 (with a continuous RMS current rating of 60A) eFuses need to be in parallel to support this customer use case.

The number required eFuses becomes half while using TI eFuse. This reduces the bill-of-material (BOM) cost of the system and improves the power density to a great extent.