SFFSAY1 October 2025 LM51261A-Q1 , LM5126A-Q1
Figure 4-2 shows the LM51261A-Q1 pin diagram for the VQFN package. For a detailed description of the device pins, see the Pin Configuration and Functions section in the LM51261A-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, 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 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 |
| SDA | 25 | I2C communication does not work. | B |
| SCL | 26 | I2C communication does not work. | B |
| CFG | 27 | Level 1 of the CFG pin is forced. | C |
| nFAULT | 28 | The voltage of the output is correct, but there is a loss of functionality at the nFAULT 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 | The device is potentially damaged. | 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 |
| SDA | 25 | I2C communication does not work. | B |
| SCL | 26 | I2C communication does not work. | B |
| CFG | 27 | Level 16 of the CFG 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 | SDA | I2C communication does not work when an external clock is used or the SYNCIN pin is connected to GND. I2C operates normally when the SYNCIN pin is left floating. The device potentially synchronizes to the SDA signal when clock synchronization is enabled. There is a loss of the frequency synchronization function. | B |
| SDA | 25 | SCL | I2C communication does not work. | B |
| SCL | 26 | CFG | I2C communication does not work for the device if the resistance of the CFG pin is strong enough to pull down the I2C clock. The device configuration for the CFG pin is incorrect. | B |
| CFG | 27 | nFAULT | The device loses the function of the configuration. | B |
| nFAULT | 28 | MODE | The MODE function of the device is effected. The device potentially functions in an operation mode that is incorrect based on the nFAULT 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 |
| SDA | 25 | Damage to the device is possible; exceeds the absolute maximum voltage rating. | A |
| SCL | 26 | Damage to the device is possible; exceeds the absolute maximum voltage rating. | A |
| CFG | 27 | Damage to the device is possible; exceeds the absolute maximum voltage rating. | A |
| nFAULT | 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 |