SLVAER7A may 2020 – april 2023 TPS7B4254-Q1
4 Pin Failure Mode Analysis (Pin FMA)
This section provides a failure mode analysis (FMA) for the pins of the TPS7B4254-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 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 TPS7B4254-Q1 pin diagram. For a detailed description of the device pins, see the Pin Configuration and Functions section in the TPS7B4254-Q1 data sheet.
Figure 4-1 Pin DiagramTable 4-2 Pin FMA for Device Pins
Short-Circuited to Ground
| Pin Name | Pin No. | Description of Potential Failure Effects | Failure Effect Class |
|---|---|---|---|
| OUT | 1 | Output voltage is near or at ground. The device is in current limit and can cycle in and out of thermal shutdown depending on power dissipation. | B |
| NC | 2 | No effect. Normal operation. | D |
| GND | 3 | No effect. Normal operation. | D |
| FB | 4 | VOUT is equal to VIN minus dropout because the pass transistor is driven to the rail. | B |
| ADJ | 5 | The low-dropout regulator (LDO) does not start up because ADJ is grounded. | B |
| GND | 6 | No effect. Normal operation. | D |
| NC | 7 | No effect. Normal operation. | D |
| IN | 8 | The output is near or at ground. | B |
Table 4-3 Pin FMA for Device Pins
Open-Circuited
| Pin Name | Pin No. | Description of Potential Failure Effects | Failure Effect Class |
|---|---|---|---|
| OUT | 1 | The load is longer regulated. | B |
| NC | 2 | No effect. Normal operation. | D |
| GND | 3 | The device is operational as long as pin 6 (GND) is still connected, but with degraded performance. | B |
| FB | 4 | The output becomes unregulated. | B |
| ADJ | 5 | The device state is unknown. The device is either on and regulated to an unknown voltage, or the device is off. | B |
| GND | 6 | The device is operational as long as pin 6 (GND) is still connected, but with degraded performance. | B |
| NC | 7 | No effect. Normal operation. | D |
| IN | 8 | The device does not operate or start up. | B |
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 |
|---|---|---|---|---|
| OUT | 1 | NC (pin 2) | No effect. Normal operation. | D |
| NC | 2 | GND (pin 3) | No effect. Normal operation. | D |
| GND | 3 | FB (pin 4) | The output is equal to the input minus dropout because the pass transistor is driven to the rail. | B |
| ADJ | 5 | GND (pin 6) | The LDO does not start up because ADJ is grounded. | B |
| GND | 6 | NC (pin 7) | No effect. Normal operation. | D |
| NC | 7 | IN (pin 8) | No effect. Normal operation. | D |
Table 4-5 Pin FMA for Device Pins
Short-Circuited to
VIN
| Pin Name | Pin No. | Description of Potential Failure Effects | Failure Effect Class |
|---|---|---|---|
| OUT | 1 | No output regulation. The output voltage is the same as the input voltage. | B |
| NC | 2 | No effect. Normal operation. | D |
| GND | 3 | No output regulation. The output is near or at ground. | B |
| FB | 4 | FB is damaged if VIN exceeds the FB maximum rated voltage. Otherwise, the pass transistor is off and the output is low. | A/B |
| ADJ | 5 | The LDO starts up or shuts down when VIN is above the ADJ threshold. The output equals the input minus the dropout voltage. | B |
| GND | 6 | No output regulation. The output is near or at ground. | B |
| NC | 7 | No effect. Normal operation. | D |
| IN | 8 | No effect. Normal operation. | D |