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

Table 3-5 and Table 3-6 show the FMEDA of the LM63625-Q1 and TPS37A-Q1, respectively, at the pin level.

Table 3-5 LM63625-Q1 FMEDA Analysis at the Pin Level
Single Point Fault Latent Fault
Pin Name Failure Mode Effect of failure mode Safety-related element to be considered in the calculations Failure Rate Failure mode that has the potential to violate the safety goal in absence of safety mechanisms Safety mechanism allowing to prevent the failure mode from violating safety goal Failure mode coverage with regard to violation of safety goal Residual or single-point failure rate Failure mode that can lead to the violation of safety goal in combination with an independent failure of another component Detection means? Safety mechanism allowing to prevent the failure mode from being latent? Failure mode coverage with respect to latent failures Latent multiple-point fault failure rate
SR/NSR FIT V/NV SM/NSM % FIT V/NV SM/NSM % FIT
SW Pin open No voltage output SR 0.292 NV 0.0000 NV 0.000
Short to ground No voltage output SR 0.063 NV 0.0000 NV 0.000
Short to BOOT No voltage output SR 0.063 NV 0.0000 NV 0.000
BOOT Pin open Loss of output regulation, low or no voltage output SR 0.292 V SM 99% 0.0029 NV 0.000
Short to ground No voltage output SR 0.063 NV 0.0000 NV 0.000
Short to VCC Loss of output regulation, low or no voltage output SR 0.063 V SM 99% 0.0006 NV 0.000
VCC Pin open No voltage output SR 0.292 NV 0.0000 NV 0.000
Short to ground No voltage output SR 0.063 NV 0.0000 NV 0.000
Short to RT In this example, VCC shorts to GND, no voltage output SR 0.063 NV 0.0000 NV 0.000
RT Pin open Switching frequency drops to zero, no voltage output SR 0.292 NV 0.0000 NV 0.000
Short to ground No effect NSR 0.063 NV 0.0000 NV 0.000
Short to VSEL No effect NSR 0.063 NV 0.0000 NV 0.000
VSEL Pin open Incorrect output voltage SR 0.292 V SM 99% 0.0029 NV 0.000
Short to ground No effect NSR 0.063 NV 0.0000 NV 0.000
Short to SYNC/MODE No effect NSR 0.063 NV 0.0000 NV 0.000
SYNC/MODE Pin open Internal pull-down place device in AUTO mode, no effect NSR 0.292 NV 0.0000 NV 0.000
Short to ground No effect NSR 0.125 NV 0.0000 NV 0.000
RESET Pin open No effect NSR 0.292 NV 0.0000 NV 0.000
Short to ground No effect NSR 0.063 NV 0.0000 NV 0.000
Short to FB Output voltage incorrect or no output SR 0.063 V SM 99% 0.0006 NV 0.000
FB Pin open Output voltage can be out of specification SR 0.292 V SM 99% 0.0029 NV 0.000
Short to ground Regulator operates at maximum duty cycle. Output voltage rises to nearly VIN SR 0.063 V SM 99% 0.0006 NV 0.000
Short to AGND Regulator operates at maximum duty cycle. Output voltage rises to nearly VIN SR 0.063 V SM 99% 0.0006 NV 0.000
AGND Pin open No voltage output SR 0.292 NV 0.0000 NV 0.000
Short to ground No effect NSR 0.063 NV 0.0000 NV 0.000
Short to EN No voltage output SR 0.063 NV 0.0000 NV 0.000
EN Pin open No voltage output SR 0.292 NV 0.0000 NV 0.000
Short to ground No voltage output SR 0.063 NV 0.0000 NV 0.000
Short to NC No effect NSR 0.063 NV 0.0000 NV 0.000
NC Pin open No effect NSR 0.292 NV 0.0000 NV 0.000
Short to ground No effect NSR 0.063 NV 0.0000 NV 0.000
Short to VIN No effect NSR 0.063 NV 0.0000 NV 0.000
VIN Pin open No voltage output SR 0.292 NV 0.0000 NV 0.000
Short to ground No voltage output SR 0.125 NV 0.0000 NV 0.000
Total 5.000 0.0113 0.000
Table 3-6 TPS37A-Q1 FMEDA Analysis at the Pin Level
Single Point Fault Latent Fault
Pin Name Failure Mode Effect of failure mode Safety-related element to be considered in the calculations Failure Rate Failure mode that has the potential to violate the safety goal in absence of safety mechanisms Safety mechanism allowing to prevent the failure mode from violating safety goal Failure mode coverage with regard to violation of safety goal Residual or single-point failure rate Failure mode that can lead to the violation of safety goal in combination with an independent failure of another component Detection means? Safety mechanism allowing to prevent the failure mode from being latent? Failure mode coverage with respect to latent failures Latent multiple-point fault failure rate
SR/NSR FIT V/NV SM/NSM % FIT V/NV SM/NSM % FIT
VDD Pin open Device Unpowered, LOSS of OV/UV monitoring SR 0.210 NV 0.0000 V NSM 0% 0.210
Short to ground Device Unpowered, LOSS of OV/UV monitoring SR 0.045 NV 0.0000 V NSM 0% 0.045
Short to SENSE1 3V3 short to VDD, OV detected NSR 0.045 NV 0.0000 NV 0.000
SENSE1 Pin open LOSS of OV monitoring SR 0.210 NV 0.0000 V NSM 0% 0.210
Short to ground LOSS of OV monitoring SR 0.045 NV 0.0000 V NSM 0% 0.045
Short to SENSE2 No effect NSR 0.045 NV 0.0000 NV 0.000
SENSE2 Pin open LOSS of UV monitoring SR 0.210 NV 0.0000 V NSM 0% 0.210
Short to ground 3V3 short to GND,UV detected NSR 0.045 NV 0.0000 NV 0.000
Short to RESET1 LOSS of UV monitoring SR 0.045 NV 0.0000 V NSM 0% 0.045
RESET1 Pin open LOSS of OV monitoring SR 0.210 NV 0.0000 V NSM 0% 0.210
Short to ground RESET1 is LOW, which is safe state NSR 0.045 NV 0.0000 NV 0.000
Short to RESET2 No effect NSR 0.045 NV 0.0000 NV 0.000
RESET2 Pin open LOSS of UV monitoring SR 0.210 NV 0.0000 V NSM 0% 0.210
Short to ground RESET2 is LOW, which is safe state NSR 0.090 NV 0.0000 NV 0.000
CTR1/MR Pin open No effect NSR 0.210 NV 0.0000 NV 0.000
Short to ground RESET1 is LOW, which is safe state NSR 0.045 NV 0.0000 NV 0.000
Short to CTS1 Unreliable timing SR 0.045 NV 0.0000 V NSM 0% 0.045
CTS1 Pin open No effect NSR 0.210 NV 0.0000 NV 0.000
Short to ground RESET1 is LOW, which is safe state NSR 0.045 NV 0.0000 NV 0.000
Short to CTS2 Unreliable timing SR 0.045 NV 0.0000 V NSM 0% 0.045
CTS2 Pin open No effect NSR 0.210 NV 0.0000 NV 0.000
Short to ground RESET2 is LOW, which is safe state NSR 0.045 NV 0.0000 NV 0.000
Short to CTR2/MR Unreliable timing SR 0.045 NV 0.0000 V NSM 0% 0.045
CTR2/MR Pin open No effect NSR 0.210 NV 0.0000 NV 0.000
Short to ground RESET2 is LOW, which is safe state NSR 0.045 NV 0.0000 NV 0.000
Short to GND RESET2 is LOW, which is safe state NSR 0.045 NV 0.0000 NV 0.000
GND Pin open Device Unpowered, LOSS of OV/UV monitoring SR 0.210 NV 0.0000 V NSM 0% 0.210
Short to ground No effect NSR 0.090 NV 0.0000 NV 0.000
Total 3.00 0.00 1.53