SFFS521 September   2022 LM5168 , LM5169

 

  1.   Trademarks
  2. 1Overview
  3. 2Functional Safety Failure In Time (FIT) Rates
  4. 3Failure Mode Distribution (FMD)
  5. 4Pin Failure Mode Analysis (Pin FMA)

Pin Failure Mode Analysis (Pin FMA)

This section provides a failure mode analysis (FMA) for the pins of the LM5168 and LM5169. The failure modes covered in this document include the typical pin-by-pin failure scenarios:

  • Pin short-circuited to ground (see Table 4-2)
  • Pin open-circuited (see Table 4-3)
  • Pin short-circuited to an adjacent pin (see Table 4-4)
  • Pin short-circuited to supply (see Table 4-5)

Table 4-2 through Table 4-5 also indicate how these pin conditions can affect the device as per the failure effects classification in Table 4-1.

Table 4-1 TI Classification of Failure Effects
ClassFailure Effects
APotential device damage that affects functionality.
BNo device damage, but loss of functionality.
CNo device damage, but performance degradation.
DNo device damage, no impact to functionality or performance.

Figure 4-1 shows the LM5168 and LM5169 pin diagram. For a detailed description of the device pins, see the Pin Configuration and Functions section in the LM5168 and LM5169 data sheet.

GUID-36EA2222-CB27-437E-830F-C258555C52F4-low.gif Figure 4-1 Pin Diagram

Following are the assumptions of use and the device configuration assumed for the pin FMA in this section:

Table 4-2 Pin FMA for Device Pins Short-Circuited to Ground
Pin Name Pin No. Description of Potential Failure Effect(s) Failure Effect Class
GND 1 Normal operation D
VIN 2 Input supply shorted to ground. No output voltage B
EN/UVLO 3 No output voltage. Loss of EN/UVLO functionality B
RT 4 No or low output voltage B
FB 5 Output voltage increases to near input voltage level. Possible damage to load B
PGOOD 6 Normal operation. Loss of PGOOD function B
BST 7 No output voltage. Possible device damage A
SW 8 No output voltage. Possible device damage A
Table 4-3 Pin FMA for Device Pins Open-Circuited
Pin NamePin No.Description of Potential Failure Effect(s)Failure Effect Class
GND1No output voltageB
VIN2No output voltageB
EN/UVLO3No output voltage. Loss of EN/UVLO functionalityB
RT 4 Output voltage out of regulation. Possible damage to load B
FB 5 Output voltage out of regulation. Possible damage to load B
PGOOD 6 Normal operation. Loss of PGOOD function B
BST 7 No output voltage B
SW 8 No output voltage B
Table 4-4 Pin FMA for Device Pins Short-Circuited to Adjacent Pin
Pin NamePin No.Shorted toDescription of Potential Failure Effect(s)Failure Effect Class
GND12, VINNo output voltage. Input supply shorted to ground.B
VIN23, EN/UVLONormal operation. Loss of EN/UVLO functionalityB
EN/UVLO34, RTNo output voltage. Possible device damageA
FB 5 6, PGOOD Output voltage out of regulation. Possible damage to load B
PGOOD 6 7, BST No output voltage B
BST 7 8, SW No output voltage B
Table 4-5 Pin FMA for Device Pins Short-Circuited to VIN
Pin NamePin No.Description of Potential Failure Effect(s)Failure Effect Class
GND1Input supply shorted. No output voltageB
VIN2Normal operationD
EN/UVLO3Normal operation. EN/UVLO functionality lostB
RT 4 No output voltage. Device damage A
FB 5 No output voltage. Device damage A
PGOOD 6 Loss of PGOOD functionality. Possible device damage A
BST 7 No output voltage. Device damage A
SW 8 Output voltage at level of input voltage. Damage to load. Possible device damage A