SFFS478 February   2024 LM74502-Q1 , LM74502H-Q1

 

  1.   1
  2.   Trademarks
  3. 1Overview
  4. 2Functional Safety Failure In Time (FIT) Rates
  5. 3Failure Mode Distribution (FMD)
  6. 4Pin Failure Mode Analysis (Pin FMA)

4 Pin Failure Mode Analysis (Pin FMA)

This section provides a Failure Mode Analysis (FMA) for the pins of the LM74502-Q1, LM74502H-Q1. 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 LM74502-Q1, LM74502H-Q1 pin diagram. For a detailed description of the device pins please refer to the Pin Configuration and Functions section in the LM74502-Q1, LM74502H-Q1 data sheet.

Figure 4-1 Pin Diagram (DDF Package)

The pin FMA is provided under the assumption that the device is operating under the specified ranges within the Recommended Operating Conditions section of the data sheet.

Table 4-2 Pin FMA for Device Pins Short-Circuited to Ground
Pin NamePin No.Description of Potential Failure Effect(s)Failure Effect Class
EN/UVLO1Device will not power up and will be in shutdown mode.B
GND2No effect on device behavior.D
N.C3No effect on the device behavior.D
VCAP4Device may heat up and damage due to increased quiescent current.A
VS5Device will not power up. This is equivalent to input supply shorted to ground.B
GATE6External MOSFET will not turn on. Device may heat up and damage due to increased quiescent current.

A

OV7Overvoltage functionality will not be available.B
SRC8Device quiescent current may increase. Based on input voltage, external MOSFET may sustain damage due to GATE to SOURCE maximum voltage specification violation.B
Table 4-3 Pin FMA for Device Pins Open-Circuited
Pin NamePin No.Description of Potential Failure Effect(s)Failure Effect Class
EN/UVLO1Device will not power up and will be in shutdown mode due to internal pull down on EN/UVLO pin.B
GND2Device will not power up.B
N.C5No effect on the device behavior.D
VCAP4Charge pump will not come up. External FET will be off.B
VS5Device will not power up. This is equivalent to input supply not available.B
GATE6External FET will not turn on.B
OV7Overvoltage functionality will not be available.B
SRC8Device will not be able to turn off external FETs completely. System will not have any protection from input reverse polarity after external FETs are turned on.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
EN/UVLO1GNDDevice will not power up and will be in shutdown mode.B
GND2N.CNo effect on the device performance.D
N.C3VCAPNo effect on the device performance.D
VCAP4-VCAP is the corner pin. No effect on the device performance.D
VS5GATEExternal FET will not turn on. Device quiescent current may increase.B
GATE6OVDevice GATE drive will be turned off due to OV comparator trigger.B
OV7SRCDevice GATE drive will be turned off due to OV comparator trigger. Device GATE pin may oscillate between on and off state.B
SRC8-SRC is the corner pin. No effect on the device performance.D
Table 4-5 Pin FMA for Device Pins Short-Circuited to supply
Pin NamePin No.Description of Potential Failure Effect(s)Failure Effect Class
EN/UVLO1Device will always be on.B
GND2Device will not power up. It is equivalent to input supply short condition.B
N.C3No effect on the device performance.D
VCAP4Device charge pump will not come up. External FET will be off.B
VS5No effect on the device performance.D
GATE6External FET will be off.B
OV7Device will be off due to OV comparator trigger.B
SRC8Device will not be able to disconnect the load from supply due to input supply to SRC pin shorting.B