SFFS719 November 2023 LMR66430 , LMR66430-Q1
4 Pin Failure Mode Analysis (Pin FMA)
This section provides a Failure Mode Analysis (FMA) for the pins of the LMR664x0 and LMR664x0-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 LMR664x0 and LMR664x0-Q1 pin diagram. For a detailed description of the device pins please refer to the Pin Configuration and Functions section in the LMR664x0 and LMR664x0-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:
- Application circuit, as per the LMR664x0 and LMR664x0-Q1 data sheets are used.
| Pin Name | Pin No. | Description of Potential Failure Effect(s) | Failure Effect Class |
|---|---|---|---|
| EN/UVLO | 1 | VOUT = 0 V, the part is disabled. | D |
| NC | 2 | VOUT is normal. | D |
| VIN | 3 | VOUT = 0 V. | B |
| NC | 4 | VOUT is normal. | D |
| NC | 5 | VOUT is normal. | D |
| PGND | 6 | VOUT is normal. | D |
| SW | 7 | Damage to HSFET. | A |
| BOOT | 8 | VOUT = 0 V, high side MOSFET won't turn on. | B |
| NC | 9 | VOUT is normal. | D |
| VCC | 10 | VOUT = 0 V. | B |
| VOUT/FB | 11 | VOUT = 0 V. | B |
| NC | 12 | VOUT is normal. | D |
| RT or MODE/SYNC | 13 | Switching frequency is 2.2 MHz. | D |
| PGOOD | 14 | When this pin is not in use it can be left grounded. PGOOD signal is not a valid signal, VOUT is normal. | D |
| Pin Name | Pin No. | Description of Potential Failure Effect(s) | Failure Effect Class |
|---|---|---|---|
| EN/UVLO | 1 | Pin cannot be left floating. | B |
| NC | 2 | VOUT is normal. | D |
| VIN | 3 | VOUT = 0 V. | B |
| NC | 4 | VOUT is normal. | D |
| NC | 5 | VOUT is normal. | D |
| PGND | 6 | VOUT can be abnormal because the reference voltage is not fixed. | B |
| SW | 7 | VOUT = 0 V. | B |
| BOOT | 8 | VOUT = 0 V, high side MOSFET does not turn on. | B |
| NC | 9 | VOUT is normal. | D |
| VCC | 10 | VCC output is unstable, can increase above 5.5 V. | A |
| VOUT/FB | 11 | VOUT = 0 V. Do not float this pin. | B |
| NC | 12 | VOUT is normal. | D |
| RT or MODE/SYNC | 13 | If it is an RT part, then the frequency is not defined. If it is a MODE/SYNC part, then the part can go back and forth between FPWM and PFM. Part is up, part functional. | D |
| PGOOD | 14 | When not in use, PGOOD can be left open. PGOOD is not a valid signal, VOUT is normal. | D |
| Pin Name | Pin No. | Shorted to | Description of Potential Failure Effect(s) | Failure Effect Class |
|---|---|---|---|---|
| EN/UVLO | 1 | NC | VOUT is normal. | D |
| NC | 2 | VIN | VOUT is normal. | D |
| VIN | 3 | NC | VOUT is normal. | D |
| NC | 4 | NC | VOUT is normal. | D |
| NC | 5 | PGND | VOUT is normal. | D |
| PGND | 6 | SW | Damage to HSFET. | A |
| SW | 7 | BOOT | VOUT = 0 V, high side MOSFET does not turn on, CBOOT capacitor is shorted. | B |
| BOOT | 8 | NC | VOUT is normal. | D |
| NC | 9 | VCC | VOUT is normal. | D |
| VCC | 10 | VOUT/FB | The part can be functional, no damage occurs. | B |
| VOUT/FB | 11 | NC | VOUT is normal. | D |
| NC | 12 | RT of MODE/SYNC | VOUT is normal. | D |
| RT or MODE/SYNC | 13 | PGOOD | The absolute maximum voltage rating of this pin is 20 V. This pin can be damaged if PGOOD goes to 20 V. | A |
| PGOOD | 14 | EN/UVLO | If EN/UVLO > 20 V, this damages devices connected to the PGOOD pin. | A |
| Pin Name | Pin No. | Description of Potential Failure Effect(s) | Failure Effect Class |
|---|---|---|---|
| EN/UVLO | 1 | VOUT is normal. | D |
| NC | 2 | VOUT is normal. | D |
| VIN | 3 | VOUT is normal. | D |
| NC | 4 | VOUT is normal. | D |
| NC | 5 | VOUT is normal. | D |
| PGND | 6 | VOUT = 0 V. | A |
| SW | 7 | Damage to LSFET. | A |
| BOOT | 8 | Damage occurs, BOOT ESD clamp is damaged. | A |
| NC | 9 | VOUT is normal. | D |
| VCC | 10 | If VIN > 5.5 V, damage occurs. | A |
| VOUT/FB | 11 | If VIN > 20 V, damage occurs. | A |
| NC | 12 | VOUT is normal. | D |
| RT or MODE/SYNC | 13 | If VIN > 5.5 V, damage occurs. If VIN < 5.5 V, the switching frequency is 1 MHz. | A |
| PGOOD | 14 | IF VIN > 20 V, damage occurs. | A |