SFFS993 October 2024 LMR51403
This section provides a failure mode analysis (FMA) for the pins of the LMR51403. 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. |
Following are the assumptions of use and the device configuration assumed for the pin FMA in this section:
Figure 4-1 shows the LMR51403 pin diagram for the SOT-23 package. For a detailed description of the device pins please refer to the Pin Configuration and Functions section in the appropriate device data sheet.
Pin Name | Pin No. | Description of Potential Failure Effects | Failure Effect Class |
---|---|---|---|
CB | 1 | No output voltage. | B |
GND | 2 | Normal operation. | D |
FB | 3 | The regulator operates at maximum duty cycle. Output voltage rises approximately to the input voltage (VIN) level. Damage to customer load and output stage components are possible. No effect on device. | B |
EN | 4 | Loss of ENABLE functionality. Device remains in shutdown mode. | B |
VIN | 5 | Device does not operate. No output voltage is generated. Output capacitors discharge through the input short. A large current reversal can damage the device. | A |
SW | 6 | Damage to internal FET. | A |
Pin Name | Pin No. | Description of Potential Failure Effects | Failure Effect Class |
---|---|---|---|
CB | 1 | No output voltage. | B |
GND | 2 | VOUT can be abnormal due to switching noise on analog circuits. | B |
FB | 3 | VOUT is higher than the programmed output voltage. | B |
EN | 4 | Loss of ENABLE functionality. Erratic operation; loss of regulation is probable. | B |
VIN | 5 | No output voltage. | B |
SW | 6 | No output voltage. | B |
Pin Name | Pin No. | Shorted to | Description of Potential Failure Effects | Failure Effect Class |
---|---|---|---|---|
CB | 1 | GND | No output voltage. | A |
GND | 2 | FB | The regulator operates at maximum duty cycle. Output voltage rises approximately to the input voltage (VIN) level. Damage to customer load and output stage components are possible. No effect on device. | B |
FB | 3 | GND | The regulator operates at maximum duty cycle. Output voltage rises approximately to the input voltage (VIN) level. Damage to customer load and output stage components are possible. No effect on device. | B |
EN | 4 | VIN | No damage to device. Loss of ENABLE functionality. | B |
VIN | 5 | SW | Damage to internal FET. | A |
SW | 6 | VIN | Damage to internal FET. | A |
Pin Name | Pin No. | Description of Potential Failure Effects | Failure Effect Class |
---|---|---|---|
CB | 1 | No output voltage. CBOOT ESD clamp runs current to destruction. | A |
GND | 2 | No output voltage. Damage to other pins referred to GND. | A |
FB | 3 | If VIN exceeds 5.5V, damage occurs. No output voltage. | A |
EN | 4 | No damage to device. Loss of ENABLE functionality. | B |
VIN | 5 | No effect. | D |
SW | 6 | Damage to low side MOSFET. | A |