SNVAA02 December 2020 LM76005-Q1
4 Pin Failure Mode Analysis (Pin FMA)
This section provides a Failure Mode Analysis (FMA) for the pins of the LM76005-Q1. 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 supply (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 LM76005-Q1 pin diagram. For a detailed description of the device pins please refer to the Pin Configuration and Functions section in the LM76005-Q1 data sheet.
Figure 4-1 Pin DiagramFollowing are the assumptions of use and the device configuration assumed for the pin FMA in this section:
- Device used within the 'Recommended Operating Conditions' and the 'Absolute Maximum Ratings' found in the LM76005-Q1 data sheet.
- Configuration as shown in the 'Example Application Circuit' found in the LM76005-Q1 data sheet.
Table 4-2 Pin FMA for Device Pins
Short-Circuited to Ground
| Pin Name | Pin No. | Description of Potential Failure Effect(s) | Failure Effect Class |
|---|---|---|---|
| SW | 1, 2, 3, 4, 5 | Damage to internal power FETs | A |
| BOOT | 6 | Damage to internal circuits | A |
| N/C | 7 | None functional pin, no connection | D |
| VCC | 8 | Fault mode will shut the device down. | B |
| BIAS | 9 | Normal operation | D |
| RT | 10 | Set to frequency much higher than 500 KHz and can cause damge to internal circuit. | B |
| SS/TRK | 11 | Set output to zero voltage. | B |
| FB | 12 | Shorting FB will cause no voltage regulation control. | B |
| AGND | 13, 14, 15 | Normal operation | D |
| PGOOD | 16 | PGOOD not valid signal, VOUT in regulation | D |
| SYNC/MODE | 17 | Shorted to GND is DCM/PFM operation | C |
| EN | 18 | Vout = 0 V | B |
| NC | 19 | None functional pin, no connection | D |
| PVIN | 20, 21, 22 | Device will not operate. | B |
| N/C | 23 | None functional pin, no connection | D |
| PGND | 24, 25, 26 | Normal operation | D |
| N/C | 27, 28, 29, 30 | None functional pin, no connection | D |
Table 4-3 Pin FMA for Device Pins
Open-Circuited
| Pin Name | Pin No. | Description of Potential Failure Effect(s) | Failure Effect Class |
|---|---|---|---|
| SW | 1, 2, 3, 4, 5 | Loss of output voltage regulation | B |
| BOOT | 6 | Loss of output voltage regulation | B |
| N/C | 7 | None functional pin, no connection | D |
| VCC | 8 | VCC will be unstable and cause damage to internal circuits. | A |
| BIAS | 9 | Normal operation | D |
| RT | 10 | Set to default frequency 400 KHz. | C |
| SS/TRK | 11 | Use the 6.3-ms internal soft-start ramp. | D |
| FB | 12 | Floating FB will cause no voltage regulation control. | B |
| AGND | 13, 14, 15 | Can cause damage to internal circuits | A |
| PGOOD | 16 | PGOOD not valid signal, VOUT in regulation | D |
| SYNC/MODE | 17 | Floating this pin can cause unexpected operation mode. | B |
| EN | 18 | Device may not power up. | B |
| NC | 19 | None functional pin, no connection | D |
| PVIN | 20, 21, 22 | Device can become damaged if only one PVIN pin is connected to PCB board. | A |
| N/C | 23 | None functional pin, no connection | D |
| PGND | 24, 25, 26 | Device can become damaged if only one PGND pin is connected to PCB board. | A |
| N/C | 27, 28, 29, 30 | None functional pin, no connection | D |
Table 4-4 Pin FMA for Device Pins
Short-Circuited to Adjacent Pin
| Pin Name | Pin No. | Description of Potential Failure Effect(s) | Failure Effect Class |
|---|---|---|---|
| SW | 1, 2, 3, 4 | SW pin 1 to pin 5 are expected to be shorted. | D |
| SW | 5 | Loss of output voltage regulation, possible damage internal circuits | A |
| BOOT | 6 | Normal operation | D |
| N/C | 7 | None functional pin, no connection | D |
| VCC | 8 | VCC will be unstable if BIAS voltage is noisy or cause damage if BIAS >5.5 V. | A |
| BIAS | 9 | Switching frequency set to near 0 Hz or damage to internal circuits > 5 V | A |
| RT | 10 | Switching frequency set to near 0 Hz. | B |
| SS/TRK | 11 | Switching frequency set to near 0 Hz. | B |
| FB | 12 | Shorting FB will cause no voltage regulation control. | B |
| AGND | 13 | Shorting FB will cause no voltage regulation control. | B |
| AGND | 14, 15 | Normal operation | D |
| PGOOD | 16 | Can cause damage to internal circuits | A |
| SYNC/MODE | 17 | If voltage exceeds 5.5 V, damage to internal circuits will happen. | A |
| EN | 18 | Normal operation | D |
| NC | 19 | None functional pin, no connection | D |
| PVIN | 20, 21, 22 | No impact | D |
| N/C | 23 | None functional pin, no connection | D |
| PGND | 24, 25, 26 | Device is operational. | D |
| N/C | 27, 28, 29, 30 | None functional pin, no connection | D |
Table 4-5 Pin FMA for Device Pins
Short-Circuited to
supply
| Pin Name | Pin No. | Description of Potential Failure Effect(s) | Failure Effect Class |
|---|---|---|---|
| SW | 1, 2, 3, 4, 5 | Damage to LS FET | A |
| BOOT | 6 | Damage to internal circuits | A |
| N/C | 7 | None functional pin, no connection | D |
| VCC | 8 | Damage if voltage exceeds 5.5 V | A |
| BIAS | 9 | Damage to internal circuits if voltage exceeds 30 V | A |
| RT | 10 | If voltage exceeds 5.5 V, damage to internal circuits will happen. | A |
| SS/TRK | 11 | If voltage exceeds 5 V, damage to internal circuits will happen. | A |
| FB | 12 | If voltage exceeds 5 V, damage to internal circuits will happen. | A |
| AGND | 13, 14, 15 | Can cause damage to internal circuits | A |
| PGOOD | 16 | Can cause damage to internal circuits if voltage exceeds 20 V | A |
| SYNC/MODE | 17 | If voltage exceeds 5.5 V, damage to internal circuits will happen. | A |
| EN | 18 | EN pin can handle ≤ 60 V. Greater than 60 V can cause damage to internal circuits. | D |
| NC | 19 | None functional pin, no connection | D |
| PVIN | 20, 21, 22 | Normal operation | D |
| N/C | 23 | None functional pin, no connection | D |
| PGND | 24, 25, 26 | Can cause damage to internal circuits or package | A |
| N/C | 27, 28, 29, 30 | None functional pin, no connection | D |