SNVA910A December 2019 – September 2024 LM4128 , LM4128-Q1
4 Pin Failure Mode Analysis (Pin FMA)
This section provides a failure mode analysis (FMA) for the pins of the LM4128 and LM4128-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.
| 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 LM4128 and LM4128-Q1 pin diagram. For a detailed description of the device pins, see the Pin Configuration and Functions section in the LM4128 and LM4128-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:
- Unless otherwise specified, the voltage applied to the VIN pin and EN pin is within the LM4128 and LM4128-Q1 Recommended Operating Range.
- The EN pin is driven from an external source.
- Device functionality indicates that the LM4128 and LM4128_Q1 status can be remotely changed between the two functional states (ENABLED and DISABLED) by the external control connected to the EN pin.
| Pin Name | Pin No. | Description of Potential Failure Effects | Failure Effect Class |
|---|---|---|---|
| NC | 1 | In the actual application, make sure the NC pin is always floating. | D |
| GND | 2 | No effect. | D |
| EN | 3 | No output voltage. Output is forced OFF. | B |
| VIN | 4 | No output voltage. | B |
| VREF | 5 | No output voltage or low output voltage. Output current is at short-circuit current limit; thermal shutdown can be activated. | B |
| Pin Name | Pin No. | Description of Potential Failure Effects | Failure Effect Class |
|---|---|---|---|
| NC | 1 | No effect. | D |
| GND | 2 | Output is not regulated. | B |
| EN | 3 | EN pin is floating and the EN pin state is indeterminable. | B |
| VIN | 4 | No output voltage. | B |
| VREF | 5 | No output voltage to load. | B |
| Pin Name | Pin No. | Shorted to | Description of Potential Failure Effects | Failure Effect Class |
|---|---|---|---|---|
| NC | 1 | GND | In the actual application, make sure the NC pin is always floating. | D |
| GND | 2 | EN | No output voltage. Output is forced OFF. | B |
| EN | 3 | Output forced ON. | B | |
| VIN | 4 | VREF | No VREF regulation. Output voltage is same as input voltage. | B |
| VREF | 5 | NC | In the actual application, make sure the NC pin is always floating. | D |
| Pin Name | Pin No. | Description of Potential Failure Effects | Failure Effect Class |
|---|---|---|---|
| NC | 1 | In the actual application, make sure the NC pin is always floating. | D |
| GND | 2 | No output voltage. | B |
| EN | 3 | Output forced ON. | B |
| VIN | 4 | No effect. | D |
| VREF | 5 | No VREF regulation. Output voltage is the same as input voltage. Power supply can experience a current increase. | B |