SFFS793 January 2024 LM63635C-Q1
4 Pin Failure Mode Analysis (Pin FMA)
This section provides a failure mode analysis (FMA) for the pins of the LM63635C-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
| Class | Failure Effects |
|---|---|
| A | Potential device damage that affects functionality. |
| B | No device damage, but loss of functionality. |
| C | No device damage, but performance degradation. |
| D | No device damage, no impact to functionality or performance. |
Figure 4-1 shows the LM63635C-Q1 pin diagram. For a detailed description of the device pins, see the Pin Configuration and Functions section in the LM63635C-Q1 data sheet.
Figure 4-1 Pin DiagramFollowing are the assumptions of use and the device configuration assumed for the pin FMA in this section:
- Device used within the 'Recommended Operating Conditions' and the 'Absolute Maximum Ratings' found in LM63635C-Q1 data sheet.
- The typical application circuit, as per the LM63635C-Q1 data sheet is used.
Table 4-2 Pin FMA for Device Pins
Short-Circuited to Ground
| Pin Name | Pin No. | Description of Potential Failure Effects | Failure Effect Class |
|---|---|---|---|
| SW | 1 | Damage to internal power FET or FETs, other internal circuits, or both | A |
| BOOT | 2 | Damage to internal circuits | A |
| N/C | 3 | No effect | D |
| VCC | 4 | Fault mode shuts the device off. | B |
| MODE | 5 | No effect | D |
| RESET | 6 | RESET functionality is lost. | B |
| FB | 7 | The regulator operates at the maximum duty cycle. The output voltage rises to nearly the input voltage (VIN) level. Possible damage to customer load, output stage components, or both, can occur. No effect on the device. | B |
| N/C | 8 | No effect | D |
| AGND | 9 | No effect | D |
| EN | 10 | Loss of ENABLE functionality The device remains in shutdown mode. | B |
| N/C | 11 | No effect | D |
| VIN | 12 | The device does not operate. No output voltage is generated. Output capacitors discharge through input short. Large reverse current can damage device. | A |
| PGND | 13 | No effect | D |
Table 4-3 Pin FMA for Device Pins Open-Circuited
| Pin Name | Pin No. | Description of Potential Failure Effects | Failure Effect Class |
|---|---|---|---|
| SW | 1 | Loss of output voltage | B |
| BOOT | 2 | Loss of output voltage regulation; low or no output voltage. Damage to the internal device. | A |
| N/C | 3 | No effect | D |
| VCC | 4 | VCC LDO is unstable. Loss of output voltage regulation and possible damage to internal circuits. | A |
| MODE | 5 | No effect | D |
| RESET | 6 | Loss of RESET functionality | B |
| FB | 7 | Loss of output voltage regulation. Output voltage can rise or fall outside of intended regulation window. Possible damage to the customer load. | B |
| N/C | 8 | No effect | D |
| AGND | 9 | Loss of output voltage regulation. Possible damage to the internal circuits. | A |
| EN | 10 | Loss of ENABLE functionality. Erratic operation; probable loss of regulation | B |
| N/C | 11 | No effect | D |
| VIN | 12 | Loss of output voltage | B |
| PGND | 13 | Possible device damage | A |
Table 4-4 Pin FMA for Device Pins
Short-Circuited to Adjacent Pin
| Pin Name | Pin No. | Shorted to | Description of Potential Failure Effects | Failure Effect Class |
|---|---|---|---|---|
| SW | 1 | BOOT | Loss of output regulation, possible damage to internal circuits | A |
| BOOT | 2 | N/C | No effect | D |
| N/C | 3 | VCC | No effect | D |
| VCC | 4 | MODE | Not switching in auto mode at light load. | B |
| MODE | 5 | RESET | Possible damage to device internal circuits | A |
| FB | 7 | N/C | No effect | D |
| N/C | 8 | AGND | No effect | D |
| AGND | 9 | EN | Loss of enable function. The devices shut down. | B |
| EN | 10 | N/C | No effect | D |
| N/C | 11 | VIN | No effect | D |
Table 4-5 Pin FMA for Device Pins Short-Circuited to
supply
| Pin Name | Pin No. | Description of Potential Failure Effects | Failure Effect Class |
|---|---|---|---|
| SW | 1 | Damage to internal power FET or FETs, other internal circuits, or both | A |
| BOOT | 2 | Damage to internal circuits | A |
| N/C | 3 | No effect | D |
| VCC | 4 | Damage to internal circuits for VIN > 5.5V | A |
| MODE | 5 | Damage to internal circuits | A |
| RESET | 6 | Damage to internal circuits | A |
| FB | 7 | Damage to internal circuits | A |
| N/C | 8 | No effect | D |
| AGND | 9 | Possible damage to internal circuits or package | A |
| EN | 10 | No damage to device. Loss of ENABLE functionality | B |
| N/C | 11 | No effect | D |
| VIN | 12 | No effect | D |
| PGND | 13 | Possible damage to internal circuits or package | A |