SFFS330 November   2021 LMR38010 , LMR38020

 

  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 LMR38010 and LMR38020. 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 LMR38010 and LMR38020 pin diagram. For a detailed description of the device pins please refer to the Pin Configuration and Functions section in the LMR38010 and LMR38020 data sheet.

GUID-11676886-6580-4C52-BCBF-602D19CF5DF4-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 Name Pin No Description of Potential Failure Effect(s) Failure Effect Class
GND 1 Normal operation D
EN 2 VOUT = 0 V B
VIN 3 VOUT = 0 V B
RT/SYNC 4 Switching frequency >> 3 MHz C
FB 5 VOUT >> than programmed output voltage B
PG 6 No power-good function B
BOOT 7 VOUT = 0 V B
SW 8 Damage to HS FET A
Table 4-3 Pin FMA for Device Pins Open-Circuited
Pin Name Pin No Description of Potential Failure Effect(s) Failure Effect Class
GND 1 VOUT can be abnormal due to switching noise on analog circuits. B
EN 2 Device can shut off. B
VIN 3 Device can shut off. B
RT/SYNC 4 Switching frequency around a few10 Hz B
FB 5 VOUT >> than programmed output voltage B
PG 6 No power-good function B
BST 7 VOUT = 0 V B
SW 8 VOUT = 0 V B
Table 4-4 Pin FMA for Device Pins Short-Circuited to Adjacent Pin
Pin Name 1 Pin Name 2 Description of Potential Failure Effect(s) Failure Effect Class
GND

EN

VOUT = 0 V B

EN

VIN

Normal VOUT operation B
VIN RT/SYNC(1) RT/SYNC Pin ESD damage if VIN > 5.5 V B
FB PG VOUT less than programmed output voltage

B

PG BOOT PGOOD pin ESD damage if BOOT pin voltage >20 V A
BOOT SW VOUT = 0 V B
VIN and RT/SYNC pin space > 0.75 mm
Table 4-5 Pin FMA for Device Pins Short-Circuited to Supply
Pin Name Pin No Description of Potential Failure Effect(s) Failure Effect Class
GND 1 VOUT = 0 V. Damage to other pins referred to GND. A
EN 2 Device enabled D
VIN 3 Normal mode D
RT/SYNC 4 RT/SYNC pin ESD damage if VIN > 5.5 V B
FB 5 If VIN exceeds 5.5 V, damage will occur. VOUT = 0 V A
PG 6 PGOOD pin ESD damage if VIN > 20 V B
BOOT 7 VOUT = 0 V. CBOOT ESD clamp will run current to destruction. A
SW 8 Damage to LS FET

A