SFFS037 January   2021 LMR36015S

 

  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 LMR36015S. 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 LMR36015S pin diagram. For a detailed description of the device pins please refer to the Pin Configuration and Functions section in the LMR36015S data sheet.

GUID-124A145A-D8C7-402D-B91C-FD4622DC21E9-low.gifFigure 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 NamePin No.Description of Potential Failure Effect(s)Failure Effect Class
PGND1,11This is the ground pin, no effect.D
VIN2,10No output voltage will be generated. Possible damage to customer input supply, PCB can occur unless customer provides protection, or both. Reverse current from the SW pin to VIN pin, due to discharge of output capacitors, can damage regulator.B
N/C3No connection when it is NOT used for SW to BOOT connection D
When used for SW to BOOT connection, as recommended, the effect is the same as for pin SW (12). A
BOOT4Driver supply to high side MOSFET will be lost. Output voltage will not be regulated. Possible damage to internal regulator and Cboot charging circuit.A
VCC5Internal circuits will be disabled. No output voltage will be generated. Possible increase in input current and possible damage to internal LDO.A
AGND6This is the ground pin, no effect.D
FB7The regulator will operate at maximum duty cycle. Output voltage will rise to nearly the input voltage level. Possible damage to customer load, output stage components can occur, or both.D
PG8This is a valid connection for the PG output. PG functionality will be lost. Damage to customer components connected to PG input can occur. D
EN9This is a valid connection for the EN input. Enable functionality will be lost; the device will remain off with no output voltage generated. Damage to customer components connected to EN input can occur.B
SW12Shorting the SW pin to ground will result in large currents through the device and subsequent damage. No output voltage will be produced.A
Table 4-3 Pin FMA for Device Pins Open-Circuited
Pin NamePin No.Description of Potential Failure Effect(s)Failure Effect Class
PGND1,11Erratic operation; probable loss of regulation. Possible output voltage increase and damage to customer loadB
VIN2,11Loss of output voltageB
N/C3No connection when it is NOT used for SW to BOOT connection. D
When used for SW to BOOT connection, as recommended, the effect is the same as for pin BOOT (4). B
BOOT4Driver supply to high side MOSFET will be lost. Output voltage will not be regulated. Low or no output voltage; erratic switching behavior B
VCC5Internal LDO may oscillate. VCC voltage will not be stable. Internal circuits will not function correctly. Output voltage may not be regulated.B
AGND6Erratic operation; probable loss of regulation. Possible output voltage increase and damage to customer loadB
FB7Device will not regulate. Output voltage can rise or fall. Damage to customer load, output stage components is probable, or both.B
PG8This is a valid connection for the PG output. PG functionality will be lost. B
EN9Loss of enable functionality. Erratic operation; probable loss of regulationB
SW12Loss of output voltageB
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
PGND1VINNo output voltage will be generated. Possible damage to customer input supply, PCB can occur unless customer provides protection, or both. Reverse current from the SW pin to VIN pin, due to discharge of output capacitors, can damage the regulator.B
VIN2N/CNo connection when NOT used for SW to BOOT connection.D
When used for SW to BOOT connection, as recommended, the output voltage will rise to the level of VIN. Customer load will be damaged.B
N/C3BOOTNo connection, when NOT used for SW to BOOT connection.D
When used for SW to BOOT connection, as recommended, large currents will flow through internal circuits. Possible damage to internal regulator and CBOOT charging circuits. No output voltage will be produced.

A

BOOT4VCCDamage to VCC regulator, other internal circuits, or both. Output voltage can be affected. A
VCC5AGNDInternal circuits will be disabled. No output voltage will be generated. Possible increase in input current and possible damage to internal LDOA
AGND6FBThe regulator will operate at maximum duty cycle. Output voltage will rise to nearly the input voltage level. Possible damage to customer load, output stage components can occur, or both. B
FB7PGErratic operation; probable loss of regulation. Possible output voltage increase and damage to customer loadB
PG8ENErratic operation; probable loss of regulation. Possible damage to customer circuits connected to these pinsB
EN9VINThis is a valid connection for the EN input. Enable functionality will be lost; the device will remain on. Damage to customer components connected to EN input can occur.D
VIN10PGNDNo output voltage will be generated. Possible damage to customer input supply, PCB can occur unless customer provides protection, or both. Reverse current from SW pin to VIN pin, due to discharge of output capacitors, can damage the regulator.B
PGND11SWShorting the SW pin to ground will result in large currents through the device and subsequent damage. No output voltage will be produced.A
Table 4-5 Pin FMA for Device Pins Short-Circuited to supply
Pin NamePin No.Description of Potential Failure Effect(s)Failure Effect Class
PGND1,11VOUT = 0 V. Damage to low-side circuitry if PGND >> AGNDA
VIN2,10Normal operationD
N/C3Normal operation when NOT used for SW to BOOT connectionD
Damage to LS FET when used for SW to BOOT connection as recommended.A
BOOT4VOUT = 0 V. CBOOT ESD clamp will run current to destruction.A
VCC5If VIN exceeds 5.5 V, damage will occur.A
AGND6VOUT = 0 V. Damage to other pins referred to GND.A
FB7If VIN exceeds 16 V, damage will occur. VOUT = 0 V.A
PG8PGOOD ESD clamp will run current to destructionA
EN9Normal operationD
SW12Damage to LS FETA