SFFSAY1 October 2025 LM51261A-Q1 , LM5126A-Q1
Figure 4-1 shows the LM5126A-Q1 pin diagram for the VQFN package. For a detailed description of the device pins, see the Pin Configuration and Functions section in the LM5126A-Q1 datasheet.
| Pin Name | Pin No. | Description of Potential Failure Effects | Failure Effect Class |
|---|---|---|---|
| DLY | 1 | The average input-current loop is not activated when the average input-current loop feature is used. | B |
| D | |||
| SS | 2 | The device does not start; no switching. | B |
| COMP | 3 | VOUT is out of regulation; not switching. | B |
| AGND | 4 | There is no effect on the device. | D |
| CSN | 5 | Damage to the device is possible if the differential voltage exceeds the absolute maximum rating of 0.3V. | A |
| CSP | 6 | Damage to the device is possible if the differential voltage exceeds the absolute maximum rating of 0.3V. | A |
| VOUT | 7 | Damage to the external components is possible. The device potentially goes into a latch state or does not start. | B |
| HO | 8 | Damage to the high-side driver is possible when the device starts switching. | A |
| HB | 9 | Damage to the device is possible when BOOT charging starts. | A |
| SW | 10 | No energy is transferred from the input to the output. | B |
| LO | 11 | Damage to the low-side driver is possible when the device starts switching. | A |
| VCC | 12 | There is a loss of VCC regulation; no switching. | B |
| PGND | 13 | There is no effect on the device. | D |
| NC | 14 | There is no effect on the device. | D |
| NC | 15 | There is no effect on the device. | D |
| NC | 16 | There is no effect on the device. | D |
| NC | 17 | There is no effect on the device. | D |
| BIAS | 18 | The device is not powered, and therefore, not functional. | B |
| UVLO/EN | 19 | The device is disabled. | B |
| NC | 20 | There is no effect on the device. | D |
| NC | 21 | There is no effect on the device. | D |
| RT | 22 | The device goes to the maximum switching frequency of >2.2MHz. | C |
| GND | 23 | There is no effect on the device. | A |
| D | |||
| SYNCIN | 24 | Clock synchronization is disabled; the device uses the internal clock. | C |
| CFG2 | 25 | Level 1 of the CFG2 pin is forced. | C |
| CFG1 | 26 | Level 1 of the CFG1 pin is forced. | C |
| CFG0 | 27 | Level 1 of the CFG0 pin is forced. | C |
| PGOOD | 28 | The voltage of the output is correct, but there is a loss of functionality at the PGOOD pin. | B |
| MODE | 29 | Diode emulation mode is activated. There is no effect if the device is configured for diode emulation mode (MODE = GND). | C |
| D | |||
| GND | 30 | There is no effect on the device. | D |
| ILIM/IMON | 31 | The average input-current loop is not activated; current monitoring does not work. | B |
| ATRK/DTRK | 32 | There is no output voltage regulation. The device enters BYPASS mode after the soft start completes. | B |
| Pin Name | Pin No. | Description of Potential Failure Effects | Failure Effect Class |
|---|---|---|---|
| DLY | 1 | Delayed programming does not work if the delay pin function is used. | B |
| D | |||
| SS | 2 | There is a short soft-start time. | C |
| COMP | 3 | The device is potentially unstable. | B |
| AGND | 4 | Damage to the device is possible. | A |
| CSN | 5 | There is a loss of the current sense signal. Peak-current limit does not work. | B |
| CSP | 6 | There is a loss of the current sense signal. Peak-current limit does not work. | B |
| VOUT | 7 | The internal feedback voltage for the regulation loop is pulled to GND; VOUT reaches OVPmax. | B |
| HO | 8 | There is a loss of the high-side driver. | B |
| HB | 9 | There is a loss of boot voltage, and hence, a loss of the high-side driver. | B |
| SW | 10 | There is a loss of the high-side driver. | B |
| LO | 11 | The low-side MOSFET does not switch. | B |
| VCC | 12 | The VCC pin is not stable enough to sustain normal operation. | B |
| PGND | 13 | Damage to the device is possible. | A |
| NC | 14 | There is no effect on the device. | D |
| NC | 15 | There is no effect on the device. | D |
| NC | 16 | There is no effect on the device. | D |
| NC | 17 | There is no effect on the device. | D |
| BIAS | 18 | The device is not powered, and therefore, the device is not functional. | B |
| UVLO/EN | 19 | The device is disabled. | B |
| NC | 20 | There is no effect on the device. | D |
| NC | 21 | There is no effect on the device. | D |
| RT | 22 | The minimum frequency is set. | C |
| GND | 23 | There is no effect on the device. | D |
| SYNCIN | 24 | Clock synchronization does not work; the device uses the internal clock. | C |
| CFG2 | 25 | Level 16 of the CFG2 pin is forced. | C |
| CFG1 | 26 | Level 16 of the CFG1 pin is forced. | C |
| CFG0 | 27 | Level 16 of the CFG0 pin is forced. | C |
| PGOOD | 28 | The output voltage is correct, but there is a loss of functionality at the PGOOD pin. | B |
| MODE | 29 | There is no effect if DEM mode is active, otherwise, DEM mode is activated. | D |
| C | |||
| GND | 30 | There is no effect on the device. | D |
| ILIM/IMON | 31 | The device operates in an average input-current limit loop operation; VOUT drops, and therefore, VOUT is out of regulation. | B |
| ATRK/DTRK | 32 | The device goes to OVPmax. | B |
| Pin Name | Pin No. | Shorted to | Description of Potential Failure Effects | Failure Effect Class |
|---|---|---|---|---|
| DLY | 1 | SS | There is a loss of the delay function; the average input-current loop does not function as intended. | B |
| SS | 2 | COMP | The device operates in peak-current limit and the output voltage rises to OVPmax. | B |
| COMP | 3 | AGND | The VOUT regulation loop does not function, the internal supply potentially collapses. | B |
| AGND | 4 | CSN | Damage to the device is possible if the differential voltage exceeds the absolute maximum rating of 0.3V. | A |
| CSN | 5 | CSP | There is a loss of current sense information. The circuit is potentially unstable. | B |
| CSP | 6 | VOUT | The output is shorted to the input supply. There is no output regulation. | B |
| VOUT | 7 | HO | Damage to the device is possible as the HO pin exceeds the absolute maximum voltage rating to switch. | A |
| HO | 8 | HB | Damage to the device is possible when switching starts. | A |
| HB | 9 | SW | There is a loss of the high-side driver. | B |
| SW | 10 | LO | Damage to the device is possible as the absolute maximum rating is exceeded at the LO pin. | A |
| LO | 11 | VCC | The LO pin does not switch. Damage to the device is possible when switching starts. | A |
| VCC | 12 | PGND | There is no VCC rail; no switching. | B |
| PGND | 13 | NC | There is no effect on the device. | D |
| NC | 14 | NC | There is no effect on the device. | D |
| NC | 15 | NC | There is no effect on the device. | D |
| NC | 16 | NC | There is no effect on the device. | D |
| NC | 17 | BIAS | There is no effect on the device. | D |
| BIAS | 18 | UVLO/EN | There is a loss of the UVLO function; the device is always enabled. | B |
| C | ||||
| UVLO/EN | 19 | NC | There is no effect on the device. | D |
| NC | 20 | NC | There is no effect on the device. | D |
| NC | 21 | RT | There is no effect on the device. | D |
| RT | 22 | GND | The device operates at the maximum switching frequency. | C |
| GND | 23 | SYNCIN | There is a loss of the frequency synchronization function; switching frequency is unstable. | B |
| SYNCIN | 24 | CFG2 | There is a loss of the frequency synchronization function or Configuration 2 is incorrect (or both—loss of function and incorrect configuration). | B |
| CFG2 | 25 | CFG1 | Configuration 1 or Configuration 2 (or both) are incorrect for the device. | B |
| CFG1 | 26 | CFG0 | Configuration 1 or Configuration 2 (or both) are incorrect for the device. | B |
| CFG0 | 27 | PGOOD | The device loses the function of Configuration 0. | B |
| PGOOD | 28 | MODE | The MODE function of the device is effected. The device potentially functions in an operation mode that is incorrect based on the PGOOD output. | C |
| MODE | 29 | GND | DEM operation MODE is selected. No effect when DEM is set as default. | B |
| D | ||||
| GND | 30 | ILIM/IMON | The function of the ILIM/IMON pin is lost. | B |
| ILIM/IMON | 31 | ATRK/DTRK | The voltage of the output is not regulated to target the intended value, and the function of the IMON/ILIM pin is lost. | B |
| ATRK/DTRK | 32 | DLY | The voltage of the output is not regulated to target the intended value. The average input-current limit does not work as intended. | B |
| Pin Name | Pin No. | Description of Potential Failure Effects | Failure Effect Class |
|---|---|---|---|
| DLY | 1 | Damage to the device is possible; exceeds the absolute maximum voltage rating. | A |
| SS | 2 | Damage to the device is possible; exceeds the absolute maximum voltage rating. | A |
| COMP | 3 | Damage to the device is possible; exceeds the absolute maximum voltage rating. | A |
| AGND | 4 | Damage to the device is possible; exceeds the absolute maximum voltage rating. | A |
| CSN | 5 | There is a loss of the current sense signal. The circuit is potentially unstable. | B |
| CSP | 6 | The device operates as normal. | D |
| VOUT | 7 | There is a loss of VOUT regulation as the output voltage is forced to VI. | B |
| HO | 8 | Damage to the device is possible as the HO pin potentially exceeds the absolute maximum voltage ratings at the pin locations of HO to SW. | A |
| HB | 9 | Damage to the device is possible as the HB pin exceeds the absolute maximum voltage ratings at the pin locations of HB to SW. | A |
| SW | 10 | Energy is not transferred from input to output. | B |
| LO | 11 | Damage to the device is possible; exceeds the absolute maximum voltage rating. | A |
| VCC | 12 | Damage to the device is possible; exceeds the absolute maximum voltage rating. | A |
| PGND | 13 | Damage to the device is possible. | A |
| NC | 14 | There is no effect on the device. | D |
| NC | 15 | There is no effect on the device. | D |
| NC | 16 | There is no effect on the device. | D |
| NC | 17 | There is no effect on the device. | D |
| BIAS | 18 | The device operates as normal. | D |
| UVLO/EN | 19 | There is no UVLO functionality, the device is enabled or disabled with VI. | B |
| C | |||
| NC | 20 | There is no effect on the device. | D |
| NC | 21 | There is no effect on the device. | D |
| RT | 22 | Damage to the device is possible; exceeds the absolute maximum voltage rating. | A |
| GND | 23 | Damage to the device is possible; exceeds the absolute maximum voltage rating. | A |
| SYNCIN | 24 | Damage to the device is possible; exceeds the absolute maximum voltage rating. | A |
| CFG2 | 25 | Damage to the device is possible; exceeds the absolute maximum voltage rating. | A |
| CFG1 | 26 | Damage to the device is possible; exceeds the absolute maximum voltage rating. | A |
| CFG0 | 27 | Damage to the device is possible; exceeds the absolute maximum voltage rating. | A |
| PGOOD | 28 | Damage to the device is possible; exceeds the absolute maximum voltage rating. | A |
| MODE | 29 | Damage to the device is possible; exceeds the absolute maximum voltage rating. | A |
| GND | 30 | Damage to the device is possible; exceeds the absolute maximum voltage rating. | A |
| ILIM/IMON | 31 | Damage to the device is possible; exceeds the absolute maximum voltage rating. | A |
| ATRK/DTRK | 32 | Damage to the device is possible; exceeds the absolute maximum voltage rating. | A |