SFFSAL1 July 2025 LM5137
4 Pin Failure Mode Analysis (Pin FMA)
This section provides a failure mode analysis (FMA) for the pins of the LM5137. 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.
Table 4-1 TI Classification of Failure Effects
| 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 LM5137 pin diagram. For a detailed description of the device pins, see the Pin Configuration and Functions section in the LM5137 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 from the LM5137 data sheet is used
- PG1 and PG2 are pulled up to VOUT1 and VOUT2, respectively
Table 4-2 Pin FMA for Device Pins Short-Circuited to
Ground
| Pin Name | Pin No. | Description of Potential Failure Effects | Failure Effect Class |
|---|---|---|---|
| FB2 | 1 | VOUT1 as expected, VOUT2 = VIN. | B |
| GND | 2 | VOUT1 and VOUT2 as expected. | D |
| VOUT2 | 3 | VOUT1 as expected, VOUT2 = 0V. Excessive current from VIN. | B |
| ISNS2+ | 4 | VOUT2 as expected, VOUT2 = oscillation. | B |
| PG2 | 5 | VOUT1 and VOUT2 as expected. PG2 forced low. | B |
| EN2 | 6 | VOUT1 as expected, VOUT2 = 0V (disabled). | B |
| GND | 7 | VOUT1 and VOUT2 as expected. | D |
| VIN | 8 | VOUT1 = 0V, VOUT2 = 0V. | A |
| HO2 | 9 | VOUT1 = 0V, VOUT = 0V. VCC regulator in current limit. | B |
| SW2 | 10 | VOUT1 as expected, VOUT2 = VIN. | B |
| CBOOT2 | 11 | VOUT1 = 0V, VOUT2 = 0V. VCC in current limit. | B |
| LO2 | 12 | VOUT1 = 0V, VOUT2 = 0V. VCC oscillation due to short through LO2 driver. | B |
| PGND | 13 | VOUT1 and VOUT2 as expected. | D |
| VCC | 14 | VOUT1 = 0V, VOUT2 = 0V. VCC regulator in current limit. | B |
| LO1 | 15 | VOUT1 = 0V, VOUT2 = 0V. VCC regulator in current limit. | B |
| CBOOT1 | 16 | VOUT1 = 0V, VOUT2 = 0V. VCC regulator in current limit. | B |
| SW1 | 17 | VOUT1 = 0V, VOUT2 as expected. | B |
| HO1 | 18 | VOUT1 = 0V, VOUT2 = 0V. VCC regulator in current limit. | B |
| GND | 19 | VOUT1 and VOUT2 as expected. | B |
| EN1 | 20 | VOUT1 = 0V (disabled), VOUT2 as expected. | B |
| PG1 | 21 | VOUT1 and VOUT2 as expected. PG1 forced low. | B |
| ISNS1+ | 22 | VOUT1 oscillation, VOUT2 as expected. | B |
| BIAS1/VOUT1 | 23 | VOUT1 = 0V, VOUT2 as expected, VOUT1 in current limit. | B |
| GND | 24 | VOUT1 and VOUT2 as expected. | D |
| FB1 | 25 | VOUT1 = VIN, VOUT2 as expected. | B |
| CNFG | 26 | (Dual) VOUT1 and VOUT2 as expected. (Interleaved) VOUT1 = as expected, VOUT2 = VIN. |
B |
| GND | 27 | VOUT1 and VOUT2 as expected. | D |
| COMP1 | 28 | VOUT1 = 0V and VOUT2 as expected. | B |
| RSS | 29 | VOUT1 and VOUT2 as expected. The soft-start time is at the minimum. | B |
| RT | 30 | VOUT1 and VOUT as expected. The oscillator is at the maximum. | B |
| AGND | 31 | VOUT1 and VOUT2 as expected. | D |
| VDDA | 32 | VOUT1 = 0V, VOUT2 = 0V, no switching. | B |
| SYNCOUT | 33 | VOUT1 and VOUT2 as expected. No SYNCOUT signal. | B |
| PFM/SYNC | 34 | VOUT1 and VOUT2 as expected. FPWM mode is always enabled. | B |
| COMP2 | 35 | VOUT1 as expected, VOUT2 = 0V. | B |
| GND | 36 | VOUT1 and VOUT2 as expected. | D |
Table 4-3 Pin FMA for Device Pins Open-Circuited
| Pin Name | Pin No. | Description of Potential Failure Effects | Failure Effect Class |
|---|---|---|---|
| FB2 | 1 | (Dual) VOUT1 as expected, VOUT2 = VIN. Possible damage. | B |
| GND | 2 | VOUT1 and VOUT2 as expected. | D |
| VOUT2 | 3 | (Internal FB) VOUT1 as expected, VOUT2 =
0V, CH2 in current limit. (External FB) VOUT1 as expected, VOUT2 = 0V, CH2 in current limit. |
B |
| ISNS2+ | 4 | VOUT1 as expected, VOUT2 oscillation, loss of current limit. | B |
| PG1 | 5 | VOUT1 and VOUT2 as expected. No PG1 signal information. | B |
| EN2 | 6 | (Floats low) VOUT1 as expected, VOUT2 =
0V, CH2 disabled. (Floats high) VOUT1 and VOUT2 as expected. |
B |
| GND | 7 | VOUT1 and VOUT2 as expected. | D |
| VIN | 8 | VOUT1 = 0V, VOUT2 = 0V. | B |
| HO2 | 9 | (Dual) VOUT1 as expected, VOUT2 =
VIN. (Interleaved) VOUT1 as expected, VOUT2 = VOUT1. |
B |
| SW2 | 10 | (Dual) VOUT1 as expected, VOUT2 = 0V.
(Interleaved) VOUT1 as expected, VOUT2 = VOUT1. |
B |
| CBOOT2 | 11 | (Dual) VOUT1 as expected, VOUT2 = VCC –
external MOSFET VTH. (Interleaved) VOUT1 as expected, VOUT2 = 0V. |
B |
| LO2 | 12 | VOUT1 as expected, VOUT2 = VIN. | B |
| PGND | 13 | VOUT1 and VOUT2 as expected. PGND connects to AGND internally. | C |
| VCC | 14 | Results in erratic switching. | B |
| LO1 | 15 | VOUT1 = VIN, low-side MOSFET damaged, VOUT2 as expected. | B |
| CBOOT1 | 16 | VOUT1 < VCC – external MOSFET VTH, VOUT2 as expected. | B |
| SW1 | 17 | VOUT1 = VCC – external MOSFET VTH, VOUT2 as expected. | B |
| HO1 | 18 | VOUT1 = VIN, VOUT2 as expected. | B |
| GND | 19 | VOUT1 and VOUT2 as expected. | D |
| EN1 | 20 | If EN1 floats high, VOUT1 as expected. If EN1 falls to < 1V, VOUT1 disables. VOUT2 as expected. | B |
| PG1 | 21 | VOUT1 as expected, VOUT2 as expected. No PG1 information. | B |
| ISNS1+ | 22 | VOUT1 oscillation, VOUT2 as expected. | B |
| BIAS1/VOUT1 | 23 | Fixed VOUT setting: VOUT2 as expected
and VOUT1 = 0V, CH1 in current limit. Adjustable VOUT setting: VOUT2 as expected and VOUT1 = 0V, CH2 in current limit. |
C |
| GND | 24 | VOUT1 and VOUT2 as expected. | D |
| FB1 | 25 | VOUT1 = VIN, VOUT2 as expected. | B |
| CNFG | 26 | VOUT1 and VOUT2 start in secondary mode. FB has no effect on COMP. If COMP voltage floats high, VOUT1 = VOUT2 = VIN. If no input on SYNCIN, then no switching and VOUT1 = VOUT2 = 0V. | B |
| GND | 27 | VOUT1 and VOUT2 as expected. | D |
| COMP1 | 28 | VOUT1 oscillation, VOUT2 as expected. | D |
| RSS | 29 | VOUT1 and VOUT2 as expected. Soft-start extends to maximum time. | |
| RT | 30 | VOUT1 = 0V and VOUT2 = 0V. No switching. | B |
| AGND | 31 | AGND connected to PGND through two internal diodes. VOUT1 3X as expected, VOUT2 3X as expected. | B |
| VDDA | 32 | VOUT1 and VOUT2 as expected. | C |
| SYNCOUT | 33 | VOUT1 and VOUT2 as expected. No SYNCOUT signal. | C |
| PFM/SYNC | 34 | VOUT1 and VOUT2 as expected. No SYNC input signal. Operation is possible in PFM or FPFM (if PFM/SYNC floats high or low, respectively). | C |
| COMP2 | 35 | (Dual) VOUT1 as expected, VOUT2
oscillation. (Interleaved) VOUT2 = VOUT1. |
B |
| GND | 36 | VOUT1 and VOUT2 as expected. | D |
Table 4-4 Pin FMA for Device Pins
Short-Circuited to Adjacent Pin
| Pin Name | Pin No. | Shorted to | Description of Potential Failure Effects | Failure Effect Class |
|---|---|---|---|---|
| FB2 | 1 | GND | VOUT1 as expected, VOUT2 = VIN. | B |
| GND | 2 | VOUT2 | VOUT1 as expected, VOUT2 = 0V. | B |
| VOUT2 | 3 | ISNS2+ | VOUT1 as expected, VOUT2 oscillation, loss of current limit for CH2. Safety mechanisms shut down CH2. | B |
| ISNS2+ | 4 | PG2 | VOUT1 oscillation, VOUT2 as expected. | B |
| PG2 | 5 | EN2 | EN2 directly connected to VIN, VOUT1 as expected, VOUT2 as expected. PG2 functionality lost. Resistive divider to VIN, VOUT1 as expected, PG2 clamps EN2 low, VOUT2 disables (0V). | B |
| EN2 | 6 | VIN | VOUT1 as expected, VOUT2 as expected. Cannot disable CH2. | C |
| GND | 7 | VIN | VOUT1 = 0V, VOUT2 = 0V. | |
| VIN | 8 | HO2 | VOUT1 as expected, VOUT2 driver damage, VOUT2 = VIN – VGS (of high-side MOSFET). | B |
| HO2 | 9 | SW2 | VOUT1 as expected, VOUT2 = 0V. VCC overcurrent condition. | B |
| SW2 | 10 | CBOOT2 | VCC regulator to hit current limit. VOUT1, VOUT2 = 0V. | B |
| CBOOT2 | 11 | LO2 | VCC regulator to hit current limit. VOUT1, VOUT2 = 0V. | D |
| LO2 | 12 | PGND | VOUT1 = 0V, VOUT2 = 0V, VCC regulator in current limit. | B |
| PGND | 13 | VCC | VOUT1 = 0V, VOUT2 = 0V. | B |
| VCC | 14 | LO1 | VOUT1 = 0V, VOUT2 = 0V. | B |
| LO1 | 15 | CBOOT1 | VOUT1 and VOUT2 as expected. | D |
| CBOOT1 | 16 | SW1 | VCC to hit current limit. VOUT1, VOUT2 = 0V. | B |
| SW1 | 17 | HO1 | VOUT1 = 0V, VOUT2 as expected. | B |
| HO1 | 18 | GND | VOUT1 = 0V, VOUT2 = 0V, VCC regulator in current limit. | B |
| GND | 19 | EN1 | If EN1 is connected through a resister divider to VIN, VOUT1 disables, VOUT2 as expected. If EN1 is connected directly to VIN, VIN is shorted to GND and VOUT1, VOUT2 disabled. | B |
| EN1 | 20 | PG1 | EN1 directly connected to VIN, VOUT2 as expected, VOUT1 as expected. PG1 functionality lost. Resistive divider to VIN, VOUT2 as expected, PG1 clamps EN1 low, VOUT1 disables (0V). | B |
| PG1 | 21 | ISNS1+ | ISNS1+ is a low-impedance pin. Very minimal loading of ISNS1+ by PG1. VOUT1 as expected with minimal error. VOUT2 as expected. | B |
| ISNS1+ | 22 | BIAS1/VOUT1 | VOUT1 oscillation, loss of current limit. VOUT2 as expected. Safety mechanisms shut down CH1. | B |
| BIAS1/VOUT1 | 23 | GND | VOUT1 = 0V, VOUT2 as expected, VOUT1 in current limit. | B |
| GND | 24 | FB1 | VOUT1 = VIN, VOUT2 as expected. | B |
| FB1 | 25 | CNFG | FB1 resistor to VDDA, the LM5137 either starts up in secondary mode or interleaved (INTLV) mode. VOUT1 = oscillated between 0V and VIN, VOUT2 = oscillation 0V to VIN. FB1 resistor divider to VOUT1, RCNFG < 71.5kΩ. The LM5137 either starts up in INTLV or single mode. VOUT1 and VOUT2 are random. | B |
| CNFG | 26 | GND | (Dual) VOUT1 as expected, VOUT2 as
expected. (Interleaved) cannot reach steady-state voltage regulation. |
B |
| GND | 27 | COMP1 | VOUT1 = 0V, VOUT2 as expected. | D |
| COMP1 | 28 | RSS | VOUT1 uncontrolled due to RSS amplifier setting COMP1 to 1V, VOUT2 as expected. | B |
| RSS | 29 | RT | VOUT1 as expected, VOUT2 as expected. Oscillator frequency is potentially altered. | B |
| RT | 30 | AGND | VOUT1 and VOUT2 as expected. Oscillator frequency is at the maximum. | C |
| AGND | 31 | VDDA | VOUT1 = 0V, VOUT2 = 0V, VDDA = 0V. | B |
| VDDA | 32 | SYNCOUT | VOUT1 as expected. VOUT2 as expected. | B |
| SYNCOUT | 33 | PFM/SYNC | If PFM/SYNC = VDDA or GND, VOUT1 as expected, VOUT2 as expected. SYNCOUT injects noise on VDDA. If there is an external CLK, the SYNCOUT driver applies a clock. | B |
| PFM/SYNC | 34 | COMP2 | PFM/SYNC = 0V, VOUT1 = 0V, VOUT2 as expected. PFM/SYNC = 5V, VOUT1 as expected, VOUT2 = VIN. PFM/SYNC = SYNC, VOUT1 as expected, VOUT2 oscillation. | B |
| COMP2 | 35 | GND | VOUT1 as expected, VOUT2 = 0V. | B |
| GND | 36 | FB2 | VOUT1 as expected, VOUT2 = VIN. | B |
Table 4-5 Pin FMA for Device Pins
Short-Circuited to VIN
| Pin Name | Pin No. | Description of Potential Failure Effects | Failure Effect Class |
|---|---|---|---|
| FB2 | 1 | If VIN < 6.5V and FB2 = VDDA, then VOUT1 as expected, VOUT2 = 3.3V. | B |
| If VIN > 6.5V, FB2 exceeds the maximum voltage rating, and FB2 is damaged. | A | ||
| GND | 2 | VOUT1 and VOUT2 = 0V, excessive current from VIN. | B |
| VOUT2 | 3 | If VIN < 85V, VOUT1 as expected, VOUT2 = VIN. | B |
| If VIN > 85V, VOUT2 exceeds the maximum voltage rating, and VOUT2 is damaged. | A | ||
| ISNS2+ | 4 | If VIN < 85V, VOUT1 as expected, VOUT2 = VIN. | B |
| If VIN > 85V, VOUT1 as expected, ISNS2+ exceeds the maximum voltage rating, and ISNS2+ is damaged. | A | ||
| PG2 | 5 | If VIN < 85V, VOUT1 and VOUT2 as expected, PG2 pulled up to VIN. | D |
| If VIN > 85V, PG2 exceeds the maximum voltage rating, and PG2 is damaged. | A | ||
| EN2 | 6 | VOUT1 and VOUT2 as expected. | D |
| GND | 7 | VOUT1 and VOUT2 = 0V, excessive current from VIN. | B |
| VIN | 8 | VOUT1 and VOUT2 as expected. | D |
| HO2 | 9 | If VIN < 6.5V, VOUT1 as expected, VOUT2 = VIN. | B |
| If VIN > 6.5V, HO2 exceeds the maximum voltage rating, and HO2 is damaged. | A | ||
| SW2 | 10 | VOUT1 as expected, VOUT2 = VIN, excessive current from VIN. | B |
| CBOOT2 | 11 | If VIN < 6.5V, VOUT1 and VOUT2 as expected. | B |
| If VIN > 6.5V, the pin exceeds the maximum voltage rating for CBOOT2 to SW2, and CBOOT2 is damaged. | A | ||
| LO2 | 12 | If VIN < 6.5V, VOUT1 and VOUT2 = 0V, excessive current from VIN. | B |
| If VIN > 6.5V, LO2 exceeds the maximum voltage rating, and LO2 is damaged. | A | ||
| PGND | 13 | VOUT1 and VOUT2 = 0V, and there is excessive current from VIN. | B |
| VCC | 14 | If VIN < 6.5V, VOUT1 and VOUT2 as expected. | D |
| If VIN > 6.5V, VCC exceeds the maximum voltage rating, and VCC is damaged. | A | ||
| LO1 | 15 | If VIN < 6.5V VOUT1 and VOUT2 = 0V, excessive current from VIN. | B |
| If VIN > 6.5V, LO1 exceeds the maximum voltage rating, and LO1 is damaged. | A | ||
| CBOOT1 | 16 | If VIN < 6.5V, VOUT1 and VOUT2 as expected. | B |
| If VIN > 6.5V, the pin exceeds the maximum rating for CBOOT1 to SW1, and CBOOT1 is damaged. | A | ||
| SW1 | 17 | VOUT1 = VIN, VOUT1 as expected, excessive current from VIN. | B |
| HO1 | 18 | If VIN < 6.5V, VOUT1 = VIN, VOUT2 as expected. | B |
| If VIN > 6.5V, HO1 exceeds the maximum voltage rating, and HO1 is damaged. | A | ||
| GND | 19 | VOUT1 and VOUT2 = 0V, and there is excessive current from VIN. | B |
| EN1 | 20 | VOUT1 and VOUT2 as expected. | D |
| PG1 | 21 | If VIN < 85V, VOUT1 and VOUT2 as expected, PG1 pulled up to VIN. | D |
| If VIN > 85V, PG1 exceeds the maximum voltage rating, and the PG1 pin is damaged. | A | ||
| ISNS1+ | 22 | If VIN < 85V, VOUT1 = VIN, VOUT2 as expected. | B |
| If VIN > 85V, VOUT1 as expected, ISNS1+ exceeds the maximum voltage rating, and ISNS1+ is damaged. | A | ||
| BIAS1/VOUT1 | 23 | If VIN < 85V, VOUT1 = VIN, VOUT2 as expected. | B |
| If VIN > 85V, BIAS1/VOUT1 exceeds the maximum voltage rating, and BIAS1/VOUT1 is damaged. | A | ||
| GND | 24 | VOUT1 and VOUT2 = 0V, and there is excessive current from VIN. | B |
| FB1 | 25 | If VIN < 6.5V and FB2 = VDDA, then VOUT1 as expected, VOUT2 = 3.3V. | B |
| If VIN > 6.5V, FB1 exceeds the maximum voltage rating, and FB1 is damaged. | A | ||
| CNFG | 26 | If VIN < 6.5V, then VOUT1 and VOUT2 as expected. | B |
| If VIN > 6.5V, CNFG exceeds the maximum voltage rating, and CNFG is damaged. | A | ||
| GND | 27 | VOUT1 and VOUT2 = 0V, and there is excessive current from VIN. | B |
| COMP1 | 28 | If VIN > 5V and < 6.5V, then VOUT1 and VOUT2 = 0V. | B |
| If VIN > 6.5V, COMP1 exceeds the maximum voltage rating, and COMP1 is damaged. | A | ||
| RSS | 29 | If VIN < 6.5V, then VOUT1 and VOUT2 as expected. | D |
| If VIN > 6.5V, RSS exceeds the maximum voltage rating, and RSS is damaged. | A | ||
| RT | 30 | If VIN < 6.5V, then VOUT1 and VOUT2 = 0V. | B |
| If VIN > 6.5V, the pin exceeds the RT maximum rating, and RT is damaged. | A | ||
| AGND | 31 | VOUT1 and VOUT2 = 0V, and there is excessive current from VIN. | B |
| VDDA | 32 | If VIN < 6.5V, then VOUT1 and VOUT2 as expected. | D |
| If VIN > 6.5V, VDDA exceeds the maximum voltage rating, and VDDA is damaged. | A | ||
| SYNCOUT | 33 | If VIN < 6.5V, then VOUT1 and VOUT2 as expected. | B |
| If VIN > 6.5V, SYNCOUT exceeds the maximum voltage rating, and SYNCOUT is damaged. | A | ||
| PFM/SYNC | 34 | If VIN < 6.5V, then VOUT1 and VOUT2 as expected. | B |
| If VIN > 6.5V, PFM/SYNC exceeds the maximum voltage rating, and PFM/SYNC is damaged. | A | ||
| COMP2 | 35 | If VIN > 5V and < 6.5V, then VOUT1 and VOUT2 = 0V. | B |
| If VIN > 6.5V, COMP2 exceeds the maximum voltage rating, and COMP2 is damaged. | A | ||
| GND | 36 | VOUT1 = 0V, VOUT2 = 0V, and there is excessive current from VIN. | B |