SFFS413 November 2022 LMR51440 , LMR51450
This section provides a Failure Mode Analysis (FMA) for the pins of the LMR51440 and LMR51450. The failure modes covered in this document include the typical pin-by-pin failure scenarios:
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.
| 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 LMR51440 and LMR51450 pin diagram. For a detailed description of the device pins please refer to the Pin Configuration and Functions section in the LMR51440 and LMR51450 data sheet.
Following are the assumptions of use and the device configuration assumed for the pin FMA in this section:
| Pin Name | Pin No. | Description of Potential Failure Effect(s) | Failure Effect Class |
|---|---|---|---|
| SW | 1 | Damage to internal power FET(s) and/or other internal circuits | A |
| SW | 2 | Damage to internal power FET(s) and/or other internal circuits | A |
| SW | 3 | Damage to internal power FET(s) and/or other internal circuits | A |
| BOOT | 4 | VOUT = 0 V, possible damage to internal circuits | A |
| PG | 5 |
No power-good function | B |
| RT | 6 |
Normal operation | D |
| FB | 7 |
The regulator operates at maximum duty cycle. Output voltage rises to nearly the input voltage (VIN) level. Possible damage to customer load and/or output stage components can occur. No effect on device. | B |
| AGND | 8 | Normal operation | D |
| EN | 9 |
Loss of ENABLE functionality Device remains in shutdown mode. | B |
| VIN | 10 |
Device does not operate. No output voltage is generated. Output capacitors discharges through input short. Large reverse current can damage device. | A |
| VIN | 11 |
Device does not operate. No output voltage is generated. Output capacitors discharges through input short. Large reverse current can damage device. | A |
| VIN | 12 |
Device does not operate. No output voltage is generated. Output capacitors discharges through input short. Large reverse current can damage device. | A |
| PGND/DAP | 13 | Normal operation | D |
| Pin Name | Pin No. | Description of Potential Failure Effect(s) | Failure Effect Class |
|---|---|---|---|
| SW | 1 |
With both pins open: loss of output voltage. With one pin open: some loss of device performance. | B |
| SW | 2 |
With both pins open: loss of output voltage. With one pin open: some loss of device performance. | B |
| SW | 3 |
With both pins open: loss of output voltage. With one pin open: some loss of device performance. | B |
| BOOT | 4 |
Loss of output voltage regulation; low or no output voltage. | B |
| PG | 5 |
No power good function | B |
| RT | 6 |
Normal operation |
D |
| FB | 7 |
Loss of output voltage regulation. Output voltage can rise or fall outside of intended regulation window. | B |
| AGND | 8 |
Loss of output voltage regulation. Possible damage to internal circuits. |
A |
| EN | 9 | Loss of ENABLE functionality. Erratic operation; probable loss of regulation. | B |
|
VIN | 10 |
With both pins open: loss of output voltage. With one pin open: possible device damage. | A |
| VIN | 11 | With both pins open: loss of output voltage. With one pin open: possible device damage. | A |
| VIN | 12 | With both pins open: loss of output voltage. With one pin open: possible device damage. | A |
| PGND/DAP | 13 | Loss of output voltage regulation. Possible damage to internal circuits. | A |
| Pin Name | Pin No. | Shorted to | Description of Potential Failure Effect(s) | Failure Effect Class |
|---|---|---|---|---|
| SW | 1 | SW | No effect | D |
| SW | 2 | SW | No effect | D |
| SW | 3 | BOOT |
VOUT = 0 V, possible damage to internal circuits | A |
| BOOT | 4 | PG | PG pin ESD damage if BOOT pin voltage > 20 V | A |
| PG | 5 | RT |
RT pin ESD damage if PG pin voltage > 5.5 V | A |
| FB | 7 | AGND |
The regulator operates at maximum duty cycle. Output voltage rises to nearly the input voltage (VIN) level. Possible damage to customer load and/or output stage components can occur. No effect on device. | B |
| AGND | 8 | EN | Loss of ENABLE functionality. Device remains in shutdown mode. | B |
| EN | 9 | VIN | Normal operation, no damage to device. Loss of ENABLE functionality. | B |
| VIN | 10 | VIN | No effect | D |
| VIN | 11 | VIN | No effect | D |
| PGND/DAP | 13 |
Any | Other pin is shorted to ground, see Table 4-2 | Any |
| Pin Name | Pin No. | Description of Potential Failure Effect(s) | Failure Effect Class |
|---|---|---|---|
| SW | 1 |
Damage to internal power FET(s) and/or other internal circuits | A |
| SW | 2 | Damage to internal power FET(s) and/or other internal circuits | A |
| SW | 3 |
Damage to internal power FET(s) and/or other internal circuits | A |
| BOOT | 4 |
VOUT = 0 V. BOOT ESD clamp runs current to destruction. | A |
| PG | 5 |
Pin ESD Damage if supply voltage > 20 V | A |
| RT | 6 |
Pin ESD Damage if supply voltage > 5.5 V | A |
| FB | 7 | If supply voltage exceeds 5.5 V damage occurs. VOUT = 0 V | A |
| AGND | 8 | Possible damage to internal circuits or package | A |
| EN | 9 | No damage to device. Loss of ENABLE functionality. | B |
| VIN | 10 | No effect | D |
| VIN | 11 | No effect | D |
| VIN | 12 | No effect | D |
| PGND/DAP | 13 | Possible damage to internal circuits or package |
A |