SFFS484A June 2022 – March 2024 LM63615-Q1 , LM63625-Q1 , LM63635-Q1
4 Pin Failure Mode Analysis (Pin FMA)
This section provides a Failure Mode Analysis (FMA) for the pins of the LM36x5C-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 (Table 4-3)
- Pin short-circuited to an adjacent pin (Table 4-4)
- Pin short-circuited to VIN (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 |
Following 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 both LM636x5-Q1 data sheet.
- Configuration as shown in the Example Application Circuit found in the LM636x5-Q1 data sheet.
Figure 4-1 shows the LM36x5C-Q1 pin diagram for the WSON package. For a detailed description of the device pins please refer to the Pin Configuration and Functions section in the LM636x5-Q1 data sheet.
Figure 4-1 Pin
Diagram for DRR0012E (WSON-12)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 |
|---|---|---|---|
| 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 |
| SYNC/MODE | 5 | Depends on exact application configuration. For the application circuit as shown in the Example Application Circuit in the device data sheet, no effect is produced. If a 0Ω jumper is used to connect the SYNC/MODE input to VCC, then the VCC output is pulled to ground; see short to ground on pin 4. | B |
| 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 Effect(s) | 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 |
| SYNC/MODE | 5 | Internal pulldown places the device in auto mode. | B |
| 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 Effect(s) | 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 | SYNC/MODE | Depends on exact application configuration. For application circuit as shown in the Example Application Circuit in the device data sheet, VCC is shorted to ground; see "short to ground on pin 4." For all other configurations, the effect is FPWM mode; loss of auto mode function. | B |
| SYNC/MODE | 5 | RESET | Depends on exact application configuration. For the application circuit as shown in the Example Application Circuit in the device data sheet, RESET is shorted to ground; see short to ground on pin 6. For all other configurations, the effect is either no change or erratic operation, loss of RESET, SYNC/MODE functionality, or both with 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 VIN
| Pin Name | Pin No. | Description of Potential Failure Effect(s) | 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 |
| SYNC/MODE | 5 | Depends on exact application configuration. For application circuit as shown in the Example Application Circuit in the device data sheet, no damage occurs. For all other configurations, damage to internal circuits occurs for VIN > 5.5V. | 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 |