SFFSA20 November 2024 LM5190
4 Pin Failure Mode Analysis (Pin FMA)
This section provides a failure mode analysis (FMA) for the pins of the LM5190 and LM25190. 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 VIN (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 LM5190 and LM25190 pin diagram. For a detailed description of the device pins please refer to the Pin Configuration and Functions section in the LM5190 and LM25190 data sheets.
Figure 4-1 Pin Diagram| Pin Name | Pin No. | Description of Potential Failure Effects | Failure Effect Class |
|---|---|---|---|
| ISET | 1 | VOUT = 0V. ISET is not functional. | B |
| RT | 2 | VOUT attempts to regulate at maximum fsw, causing maximum power dissipation. | C |
| COMP | 3 | VOUT = 0V. | B |
| FB | 4 | VOUT target set to 5V. | B |
| AGND | 5 | AGND is GND. VOUT = expected VOUT. | D |
| IMON/ILIM | 6 | VOUT = expected VOUT. Current monitor and CC limit are not functional. | B |
| VCC | 7 | VOUT = 0V, no switching, loaded VCC output. | B |
| PGND | 8 | PGND is GND. VOUT = expected VOUT. | D |
| LO | 9 | VOUT = 0V, the VCC regulator is loaded to current limit. | B |
| VIN | 10 | VOUT = 0V. | B |
| HO | 11 | VOUT = 0V, the VCC regulator is loaded to current limit. | B |
| SW | 12 | VOUT = 0V. High-side FET is shorted from VIN to GND. | A |
| CBOOT | 13 | VOUT = 0V. High-side FET is shorted from VIN to GND. | B |
| BIAS | 14 | VOUT = expected VOUT. Internal VCC regulator provides bias voltage. | C |
| PGOOD | 15 | VOUT = expected VOUT. PGOOD is not functional. | C |
| FPWM/SYNC | 16 | VOUT = expected VOUT. No synchronization is available and always in PFM mode. | C |
| EN | 17 | VOUT = 0V. Always in shutdown. | B |
| ISNS+ | 18 | VOUT = 0V. | A |
| VOUT | 19 | VOUT = 0V. | B |
| Pin Name | Pin No. | Description of Potential Failure Effects | Failure Effect Class |
|---|---|---|---|
| ISET | 1 | VOUT = expected VOUT. ISET is not functional. | C |
| RT | 2 | RT regulates to 1V, but the internal oscillator does not function. | B |
| COMP | 3 | VOUT oscillates. | A |
| FB | 4 | VOUT = VIN. | A |
| AGND | 5 | VOUT is indeterminate. | B |
| IMON/ILIM | 6 | VOUT = 0V. Current monitor and CC limit are not functional. | B |
| VCC | 7 | VOUT = 0V. | B |
| PGND | 8 | VOUT = 0V. | B |
| LO | 9 | VOUT = expected VOUT with reduced efficiency. | C |
| VIN | 10 | VOUT = 0V. | B |
| HO | 11 | If HO is opened while HO to SW has voltage, the high-side FET never turns off. VOUT = VIN. | A |
| SW | 12 | VOUT is indeterminate. The CBOOT floating rail has no reference to the actual SW node. VOUT = VIN. | A |
| CBOOT | 13 | VOUT = 0V. | B |
| BIAS | 14 | VOUT = expected VOUT. Internal VCC regulator provides bias voltage. | C |
| PGOOD | 15 | VOUT = expected VOUT. PGOOD is not functional. | C |
| FPWM/SYNC | 16 | VOUT = expected VOUT. No synchronization is available and always in FPWM mode. | C |
| EN | 17 | VOUT = 0V. | B |
| ISNS+ | 18 | The open ISNS+ pin blocks current limit and causes VOUT oscillations. | A |
| VOUT | 19 | VOUT = 0V, if the internal feedback is used. | B |
| Pin Name | Pin No. | Shorted to | Description of Potential Failure Effects | Failure Effect Class |
|---|---|---|---|---|
| ISET | 1 | RT |
If RT resistor is tied to VCC, ISET pin can be damaged. If RT resistor is tied to AGND, VOUT = expected VOUT. The switching frequency is lower. CC operation is affected. |
A |
| RT | 2 | COMP |
If RT resistor is tied to VCC, COMP pin can be damaged. If RT resistor is tied to AGND, VOUT = 0V. |
A |
| COMP | 3 | FB | External FB mode: COMP regulates to 0.8V and output is unregulated. VOUT = indeterminate. | B |
| Internal FB mode FB = VCC, device is damaged. | A | |||
| Internal FB mode FB = GND, VOUT = 0V. | B | |||
| FB | 4 | AGND | VOUT target set to 5V. | B |
| AGND | 5 | IMON/ILIM | VOUT = expected VOUT. Current monitor and CC limit are not functional. | C |
| IMON/ILIM | 6 | VCC | Device damage. | A |
| VCC | 7 | PGND | VCC is grounded. VOUT = 0V. | B |
| PGND | 8 | LO | VOUT = 0V. VCC is loaded by the LO driver. | B |
| LO | 9 | VIN | VOUT = 0V. The driver is damaged if VIN > 8V. | A |
| VIN | 10 | HO |
For VIN > 8V, exceeds the maximum ratings and the HO pin is damaged. For VIN < 8V, VOUT = dropout lower than VIN, no switching, and excess current from VIN. |
A |
| HO | 11 | SW | VOUT = 0V. | B |
| SW | 12 | CBOOT | VOUT = 0V. | B |
| CBOOT | 13 | BIAS | Device damage if CBOOT > 30V. | A |
| BIAS | 14 | PGOOD | PG pulldown can damage. VOUT = expected VOUT. | A |
| PGOOD | 15 | FPWM/SYNC |
VOUT = expected VOUT. If FPWM is tied to VCC, PG pulldown can be damaged. |
A |
| FPWM/SYNC | 16 | EN | VOUT = expected VOUT. | A |
| EN | 17 | ISNS+ | EN is high-voltage rated. VOUT = expected VOUT if VOUT > 1V. If VOUT < 1V, the device is disabled. | B |
| ISNS+ | 18 | VOUT |
Current limit is disabled since the current limit resistor is shorted. VOUT cannot regulate since current-mode feedback is shorted. |
A |
| VOUT | 19 | ISET |
VOUT = 0V. If prebias VOUT > 5.5V, ISET pin is damaged. |
A |
| Pin Name | Pin No. | Description of Potential Failure Effects | Failure Effect Class |
|---|---|---|---|
| ISET | 1 | Device damage if VIN > 5.5V. | A |
| RT | 2 |
Device damage if VIN > 8V. |
A |
| COMP | 3 |
Device damage if VIN > 5.5V If VIN < 5.5V, VOUT out of regulation. |
A |
| FB | 4 |
Device damage if VIN > 8V. If VIN < 8V, VOUT = VIN. |
A |
| AGND | 5 | VOUT = 0V. | B |
| IMON/ILIM | 6 | Device damage if VIN > 5.5V. | A |
| VCC | 7 |
Device damage if VIN > 8V. If VIN < 8V, VOUT = expected VOUT. |
A |
| PGND | 8 | VOUT = 0V. | B |
| LO | 9 | VOUT = 0V. The driver is damaged if VIN > 8V. | A |
| VIN | 10 | N/A | D |
| HO | 11 |
For VIN > 8V, exceeds maximum ratings and the HO pin is damaged For VIN < 8V, VOUT = dropout lower than VIN, no switching, and excess current from VIN |
A |
| SW | 12 | VOUT = VIN, excess current from VIN. LO turns on and shorts against VIN. | B |
| CBOOT | 13 |
Device damage if VIN > 8V. If VIN < 8V, VOUT < expected VOUT. |
A |
| BIAS | 14 | Device damage if VIN > 30V. | A |
| PGOOD | 15 | Device damage. | A |
| FPWM/SYNC | 16 |
Device damage if VIN > 8V. If VIN < 8V, VOUT = expected VOUT but always FPWM mode. |
A |
| EN | 17 | Always on. VOUT = expected VOUT. | C |
| ISNS+ | 18 | Device damage. | A |
| VOUT | 19 | VOUT = VIN. | B |