SNVA924A December 2019 – May 2022 LM25141-Q1 , LM5141-Q1
This section provides a Failure Mode Analysis (FMA) for the pins of the LM25141-Q1. 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 LM25141-Q1 pin diagram. For a detailed description of the device pins, please refer to the Pin Configuration and Functions section in the LM25141-Q1 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 |
|---|---|---|---|
| DEMB | 1 | VOUT = expected, DEMB mode only, and no synchronization is available. | C |
| If DEMB = VDDA, VOUT = 0 V. Loaded VCC output | B | ||
| VDDA | 2 | VOUT = 0 V. No switching. Loaded VCC output | B |
| AGND | 3 | AGND is GND. VOUT = expected | D |
| RT | 4 | Normal operation. VOUT = expected. FSW defaults to 2.2 MHz or 440 kHz, depending on OSC. | C |
| DITH | 5 | Dither disabled. VOUT = expected | C |
| OSC | 6 | If OSC = GND, then FSW = 440 kHz. VOUT = expected | C |
| If OSC = VDDA, then VOUT = 0 V. Loaded VCC output | |||
| LOL | 7 | VOUT = 0 V. The VCC regulator is loaded to current limit. | B |
| LO | 8 | VOUT = 0 V. The VCC regulator is loaded to current limit. | B |
| PGND | 9 | PGND is GND. VOUT = expected | D |
| VCC | 10 | VOUT = 0 V. The VCC regulator is loaded to current limit. | B |
| HB | 11 | VOUT = 0 V. The VCC regulator is loaded to current limit. | B |
| SW | 12 | VOUT = 0 V. Excessive current from VIN | B |
| HO | 13 | VOUT = 0 V. High-side MOSFET cannot be turned on. | B |
| HOL | 14 | VOUT = 0 V. High-side MOSFET cannot be turned on. | B |
| VIN | 15 | VOUT = 0 V | B |
| VCCX | 16 | VOUT = expected. The internal VCC regulator provides bias voltage. | C |
| VOUT | 17 | VOUT = 0 V. Current limit reached and hiccup mode occurs. | B |
| CS | 18 | VOUT = 0 V | B |
| FB | 19 | If FB = VDDA, then VOUT = 0 V. | D |
| If FB = GND, then VOUT = 5 V. | B | ||
| COMP | 20 | VOUT = 0 V | B |
| PG | 21 | VPG = 0 V. VOUT = expected | C |
| SS | 22 | VOUT = 0 V | C |
| EN | 23 | VOUT = 0 V. The LM25141-Q1 is disabled and enters shutdown. | C |
| RES | 24 | VOUT = expected. The LM25141-Q1 cannot exit hiccup mode. | C |
| Pin Name | Pin No. | Description of Potential Failure Effect(s) | Failure Effect Class |
|---|---|---|---|
| DEMB | 1 | Diode emulation/FPWM mode undefined. VOUT = expected, erratic switching | C |
| VDDA | 2 | VOUT = 0 V. Poor noise immunity | C |
| AGND | 3 | VOUT = 0 V | B |
| RT | 4 | Normal operation. Frequency modulation feature is disabled. VOUT = expected | C |
| DITH | 5 | VOUT = expected | C |
| OSC | 6 | FSW 440 kHz or 2.2 MHz. VOUT = expected | C |
| LOL | 7 | VOUT = 0 V. No discharge path for low-side MOSFET gate | B |
| LO | 8 | VOUT = expected. Lower efficiency | C |
| PGND | 9 | VOUT = 0 V. Uncontrolled behavior because of floating ground | B |
| VCC | 10 | VOUT = 0 V | B |
| HB | 11 | VOUT = 0 V. High-side gate drive floating | B |
| SW | 12 | VOUT = VIN. High-side FET control floating | B |
| HO | 13 | VOUT = 0 V. Does not regulate | B |
| HOL | 14 | VOUT = VIN. Does not regulate. Excessive current from VIN | B |
| VIN | 15 | VOUT = 0 V | B |
| VCCX | 16 | VOUT = expected | D |
| VOUT | 17 | VOUT = oscillation. Does not regulate | B |
| CS | 18 | VOUT = oscillation. No overcurrent or current sense information for current mode control. | B |
| FB | 19 | VOUT does not regulate. The controller is configured for adjustable output. | B |
| COMP | 20 | VOUT = oscillation. Does not regulate | B |
| PG | 21 | VOUT = expected. No PG information | C |
| SS | 22 | VOUT = expected | D |
| EN | 23 | VOUT = 0 V | B |
| RES | 24 | VOUT = expected. Exits hiccup mode quickly because low parasitic capacitor value. | C |
| Pin Name | Pin No. | Shorted To | Description of Potential Failure Effect(s) | Failure Effect Class |
|---|---|---|---|---|
| DEMB | 1 | VDDA | VOUT = regulation, normal operation, and FPWM mode is enabled. | C |
| VDDA | 2 | AGND | VOUT = 0 V | B |
| AGND | 3 | RT | VOUT = regulation. Frequency modulation is disabled. | C |
| RT | 4 | DITH | VOUT = regulation. Frequency modulation is disabled. | C |
| DITH | 5 | OSC | VOUT = regulation. FSW = 440 kHz | C |
| OSC | 6 | LOL | VOUT = unregulated | B |
| LOL | 7 | LO | VOUT = expected | C |
| LO | 8 | PGND | VOUT = 0 V | B |
| PGND | 9 | VCC | VOUT = 0 V | B |
| VCC | 10 | HB | VOUT = 0 V | B |
| HB | 11 | SW | VOUT = 0 V. The VCC regulator is in current limit. | B |
| SW | 12 | HO | VOUT = 0 V | B |
| HO | 13 | HOL | VOUT = expected | B |
| HOL | 14 | VIN | VOUT = 0 V | A |
| VIN | 15 | VCCX | If VVIN > 6.5 V, then VOUT = 0 V. Exceeds the VCCX absolute maximum ratings | A |
| VCCX | 16 | VOUT | VOUT = expected | D |
| If VOUT is > 6.5 V, then it exceeds the VCCX absolute maximum rating. | A | |||
| VOUT | 17 | CS | VOUT cannot regulate, current limit is disabled, and there is no current sense information. | B |
| CS | 18 | FB | If FB = VDDA, then VOUT = 3.3 V. | B |
| If FB = GND, then VOUT = 0 V. Excessive current from VIN | B | |||
| FB | 19 | COMP | If FB = VDDA, then VOUT = VIN. | A |
| If FB = GND, then VOUT = 0 V. | B | |||
| COMP | 20 | PG | VOUT = 0 V | B |
| PG | 21 | SS | VOUT = 0 V | B |
| SS | 22 | EN | If VEN > 6.5 V, then the pin exceeds the absolute maximum rating of the SS pin. VOUT = 0 V | A |
| EN | 23 | RES | If VEN > 6.5 V, then the pin exceeds the absolute maximum rating of the SS pin. VOUT = 0 V | A |
| RES | 24 | DEMB | If DEMB = GND, VOUT = regulation, then the pin does not restart if current limit is reached. | B |
| If DEMB = VDDA, then VOUT = regulation. No hiccup mode | B |
| Pin Name | Pin No. | Description of Potential Failure Effect(s) | Failure Effect Class |
|---|---|---|---|
| DEMB | 1 | If DEMB = GND, then VOUT = 0 V. Excessive current for VIN | B |
| If DEMB = VDDA and VVIN < 6.5 V, then VOUT = expected and there is erratic switching. | B | ||
| If VVIN > 6.5 V and exceeds the maximum rating of the DEMP pin, the device is damaged. | A | ||
| VDDA | 2 | If VVIN > 6.5 V, VOUT = 0 V, and exceeds the maximum rating of the VDDA pin, the device is damaged. | A |
| If VVIN < 6.5 V, then VOUT = expected. | D | ||
| AGND | 3 | High VIN current. VOUT = 0 V | B |
| RT | 4 | If VVIN < 6.5 V, then VOUT = 0 V. | B |
| If VVIN > 6.5 V and exceeds the maximum ratings, then the device is damaged. | A | ||
| DITH | 5 | If VVIN > 6.5 V, the device is damaged. | A |
| If VVIN < 6.5 V, OUT = expected. No spread spectrum | C | ||
| OSC | 6 | If OSC = GND and high VIN current, then VOUT = 0 V. | B |
| If OSC = VDDA, VIN > 6.5 V, the device is damaged, and VOUT = 0 V. | A | ||
| If OSC = VDDA, VIN < 6.5 V, VOUT = expected, and there is erratic switching. | C | ||
| LOL | 7 | If VVIN < 6.5 V, VOUT = 0 V and there is excessive current from VIN. | B |
| If VVIN > 6.5 V, exceeds the maximum ratings for the LO pin and the device is damaged. | A | ||
| LO | 8 | If VVIN < 6.5 V, VOUT = 0 V and there is excessive current from VIN. | B |
| If VVIN > 6.5 V, exceeds the maximum ratings for the LOL pin, the device is damaged | A | ||
| PGND | 9 | VOUT = 0 V. Excessive current from VIN | B |
| VCC | 10 | If VVIN < 6.5 V, then VOUT = expected. | D |
| If VVIN > 6.5 V, exceeds the maximum ratings and the device is damaged. | A | ||
| HB | 11 | If VVIN < 6.5 V, then VOUT = expected and there is erratic switching. | B |
| If VVIN > 6.5 V, exceeds the maximum rating the device is damaged and VOUT = VIN. | A | ||
| SW | 12 | VOUT = VIN. Excessive current from VIN | A |
| HO | 13 | If VVIN < 6.5 V, VOUT drops lower than VIN, no switching, and excessive current from VIN. | B |
| If VVIN > 6.5 V, exceeds maximum ratings of the HO pin, the device is damaged, and VOUT = VIN. | A | ||
| HOL | 14 | If VVIN < 6.5 V, VOUT drops lower than VIN, no switching, and excessive current from VIN. | B |
| If VVIN > 6.5 V, exceeds maximum ratings of the HO pin, the device is damaged, and VOUT = VIN. | |||
| VIN | 15 | N/A | B |
| VCCX | 16 | For VCCX = VOUT, VIN < 6.5 V and VOUT = VIN. | B |
| If VVIN > 6.5 V, it exceeds the VCCX pin maximum rated voltage and the LM25141-Q1 is damaged. | A | ||
| VOUT | 17 | If VVIN < 15.5 V, VOUT = VIN. | B |
| If VVIN > 15.5 V and exceeds the maximum rating, the LM25141-Q1 is damaged. | A | ||
| CS | VVIN < 6.5 V. VOUT = VIN | B | |
| If VVIN > 15.5 V and exceeds the maximum rating, the LM25141-Q1 is damaged. | A | ||
| FB | 19 | If VVIN < 6.5 V, FB = VDDA, then VOUT = expected. | B |
| If VVIN < 6.5 V, FB = GND, then VOUT = 0 V. Excessive current from VIN | B | ||
| If VVIN > 6.5 V and exceeds the maximum ratings, the LM25141-Q1 is damaged. | A | ||
| COMP | 20 | If VVIN > 5 V and < 6.5 V, VOUT = 0 V | B |
| If VVIN > 6.5 V and exceeds the maximum ratings, the LM25141-Q1 is damaged. | A | ||
| PG | 21 | If VVIN < 6.5 V, VOUT = expected and PG forced high. | B |
| If VVIN > 6.5 V and exceeds the maximum ratings, the LM25141-Q1 is damaged. | A | ||
| SS | 22 | If VVIN < 6.5 V, then VOUT = expected. | D |
| If VVIN > 6.5 V and exceeds the maximum ratings, the LM25141-Q1 is damaged. | A | ||
| EN | 23 | VOUT = expected | D |
| RES | 24 | If VVIN < 6.5 V, VOUT = expected. No hiccup mode | C |
| If VVIN > 6.5 V and exceeds the maximum ratings, the LM25141-Q1 is damaged. | A |