SNVAA92 November   2023 LM63625-Q1 , TPS37-Q1 , TPS3703-Q1 , TPS3850-Q1

 

  1.   1
  2.   Abstract
  3. 1Introduction
  4. 2Power Designs for Safety MCUs With Functional Safety Requirements
  5. 3ASIL B Power-Supply Design Example and FMEDA Analysis
    1. 3.1 Functional Safety Requirements
    2. 3.2 Proposed Power Design
    3. 3.3 FMD and Pin FMA
    4. 3.4 LM63625-Q1 and TPS37A-Q1 FMEDA Analysis at the Die Level
    5. 3.5 LM63625-Q1 and TPS37A-Q1 FMEDA Analysis at the Pin Level
      1.      11
    6. 3.6 Total FMEDA Analysis of the LM63625-Q1 and TPS37A-Q1
  6. 4Summary
  7. 5Additional Resources

3.5 LM63625-Q1 and TPS37A-Q1 FMEDA Analysis at the Pin Level

Table 3-2 shows the FMEDA analysis at the die level, while Table 3-3 and Table 3-4 detail the package (pin)-level analysis. Four failure modes are usually considered for each pin: pin open, pin short to GND, pin short to adjacent pin, and pin short to power supply. These four failure modes are evenly distributed, many TI products follow this empirical distribution. For the LM63625-Q1 and TPS37A-Q1 devices; however, the pin FMDs in Table 3-3 and Table 3-4 are adjusted based on the specific integrated circuit (IC) design and simulation results. The reason is that the Pin short to VIN fault rate is very low, most likely resulting in a pin open failure mode in the LM63625-Q1 and TPS37A-Q1.

Table 3-3 LM63625-Q1 FMD at the Pin Level
Package FIT 5 FIT
Pin numbers 12
FIT for each pin 5 / 12 = 0.417 FIT
Failure mode for each pin Distribution FIT for each failure mode
Pin open 70% 0.417 × 70% = 0.292 FIT
Pin short to GND 15% 0.417 × 15% = 0.063 FIT
Pin short to adjacent pin 15% 0.417 × 15% = 0.063 FIT
Table 3-4 TPS37A-Q1 FMD at the Pin Level
Package FIT 3 FIT
Pin numbers 10
FIT for each pin 3 / 10 = 0.3 FIT
Failure mode for each pin Distribution FIT for each failure mode
Pin open 70% 0.3 × 70% = 0.21 FIT
Pin short to GND 15% 0.3 × 15% = 0.045 FIT
Pin short to adjacent pin 15% 0.3 × 15% = 0.045 FIT