SFFS750 December   2023 TPS55289-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 TPS55289-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 TPS55289-Q1 pin diagram. For a detailed description of the device pins, see the Pin Configuration and Functions section in the TPS55289-Q1 data sheet.

GUID-20231105-SS0I-FDGV-JZPP-8SBWT0LJ5TPM-low.svg Figure 4-1 TPS55289-Q1 Pin Diagram

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

  • The device is used within the Recommended Operating Conditions and the Absolute Maximum Ratings in the TPS55289-Q1 data sheet.

    The configuration is as shown in the Application and Implementation section found in the TPS55289-Q1 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/UVLO1Loss of ENABLE functionality. The device remains in shutdown mode.B
MODE2The device I2C address is fixed at 75H. Loss of I2C configuration when application target address is 74H.B
SCL3There is no output voltage.B
SDA4There is no output voltage.B
DITH/SYNC5Correct output voltage. Loss of DITH/SYNC functionality.C
FSW6Possible device damage.A
VIN7The device does not operate. Power supply is short.B
SW18Possible device damage.A
PGND9No effect.D
SW210Possible device damage.A
VOUT11The device remains in hiccup output short circuit protection mode.B
ISP12The device remains in hiccup output short circuit protection mode.B
ISN13No output voltage.B
FB/INT14When internal feedback is used, this pin always indicates low even in the normal condition. When external feedback is used, OVP is triggered.B
COMP15The output voltage is out of regulation.B
CDC16Loss of the cable voltage droop compensation functionality and the output voltage is overcompensated.B
AGND17The internal circuited can be disturbed.C
VCC18The device does not operate. VCC is short.B
BOOT219No output voltage.B
BOOT120No output voltage.B
EXTVCC21The device selects the external power supply to supply the device through the VCC pin. If there is no external 5-V rail supplying VCC, the device does not operate and output is 0 V. If there is external 5-V rail supplying VCC, no effect on device operating.B
Table 4-3 Pin FMA for Device Pins Open-Circuited
Pin Name Pin No. Description of Potential Failure Effect(s) Failure Effect Class
EN/UVLO 1 No output voltage. Loss of ENABLE functionality. B
MODE 2 The I2C target address is not fixed. B
SCL 3 There is no output voltage. B
SDA 4 There is no output voltage. B
DITH/SYNC 5 Correct output voltage. Loss of DITH/SYNC functionality. C
FSW 6 No output voltage. B
VIN 7 The device does not work and there is no output voltage. B
SW1 8 Possible device damage. A
PGND 9 Possible device damage. A
SW2 10 Possible device damage. A
VOUT 11 Possible device damage. A
ISP 12 No output voltage. B
ISN 13 The output voltage is out of regulation. B
FB/INT 14 There is a loss of the FAULT indicator function when internal feedback is used. OVP is triggered when external feedback is used. B
COMP 15 Output voltage is out of regulation. B
CDC 16 Loss of CDC functionality and no cable voltage drop compensation. C
AGND 17 Possible device damage. A
VCC 18 Possible device damage. A
BOOT2 19 Possible device damage. A
BOOT1 20 Possible device damage. A
EXTVCC 21 The device always selects internal LDO as VCC source. Loss of external VCC supply functionality. C
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/UVLO1MODEThe MODE pin is damaged if EN/UVLO pin is higher than 6 V.A
MODE2SCLThere is no output voltage.B
SCL3SDAThere is no output voltage.B
SDA4DITH/SYNCThere is no output voltage.B
DITH/SYNC5FSWPossible device damage.A
FSW6VINThe FSW pin is damaged if VIN pin is higher than 6 V.A
VIN7SW1Possible device damage.A
SW18PGNDPossible device damage.A
PGND9SW2Possible device damage.A
SW210VOUTPossible device damage.A
VOUT11ISPOutput current limit accuracy is affected.C
ISP12ISNCorrect output voltage. Loss of output current limit functionality.C
ISN13FB/INTThe FB/INT pin is damaged if ISN is higher than 6V.A
FB/INT14COMPOutput voltage is out of regulation.B
COMP15CDCOutput voltage is out of regulation.B
CDC16AGNDLoss of the cable voltage droop compensation functionality and the output voltage is overcompensated.B
AGND17VCCThe device does not operate. VCC is short. B
VCC18BOOT2The VCC pin is damaged if BOOT2 is higher than 6 V. A
BOOT219VOUTPossible device damage.A
BOOT120VINPossible device damage.A
BOOT120EXTVCCPossible device damage.A
EXTVCC21EN/UVLOEXTVCC pin is damaged if EN/UVLO pin is higher than 6 V.A
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
EN/UVLO 1 The EN/UVLO pin is damaged if supply voltage is higher than 20 V. A
MODE 2 The MODE pin is damaged if supply voltage is higher than 6 V. A
SCL 3 The SCL pin is damaged if supply voltage is higher than 6 V. A
SDA 4 The SDA pin is damaged if supply voltage is higher than 6 V. A
DITH/SYNC 5 The DITH/SYNC pin is damaged if supply voltage is higher than 6 V. A
FSW 6 The FSW pin is damaged if supply voltage is higher than 6 V. A
VIN 7 No effect. D
SW1 8 Possible device damage. A
PGND 9 The device does not operate. Power supply is short. B
SW2 10 The device is damaged if supply voltage is higher than 25 V. A
VOUT 11 The VOUT pin is damaged if supply voltage is higher than 25 V. The output voltage is equal to the supply voltage. A
ISP 12 The ISP pin is damaged if supply voltage is higher than 25 V. The output voltage is equal to the supply voltage. A
ISN 13 The ISN pin damaged if supply voltage is higher than 25 V. The output voltage is equal to the supply voltage. A
FB/INT 14 The FB/INT pin is damaged if supply voltage is higher than 6 V. A
COMP 15 The COMP pin is damaged if supply voltage is higher than 6 V. A
CDC 16 The CDC pin is damaged if supply voltage is higher than 6 V. A
AGND 17 The device does not operate. Power supply is short. B
VCC 18 The VCC pin is damaged if supply voltage is higher than 6 V. A
BOOT2 19 The BOOT2 pin is damaged if supply voltage is higher than 31 V. A
BOOT1 20 Possible device damage. A
EXTVCC 21 The EXTVCC pin is damaged if supply voltage is higher than 6 V. A