SFFS764 July 2024 REF35-Q1
4 Pin Failure Mode Analysis (Pin FMA)
This section provides a failure mode analysis (FMA) for the pins of the REF35-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 REF35-Q1 pin diagram. For a detailed description of the device pins, see the Pin Configuration and Functions section in the REF35-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:
- VIN = 2.2V, VREF = 1.8V
- NR and EN pins are open.
- CIN = 0.1uF and CREF = 1uF
Table 4-2 Pin FMA for Device Pins Short-Circuited to Ground
| Pin Name | Pin No. | Description of Potential Failure Effects | Failure Effect Class |
|---|---|---|---|
| GND | 1 | Normal Operation. | D |
| GND | 2 | Normal Operation. | D |
| EN | 3 | The device is in shutdown mode. | B |
| VIN | 4 | The device has no power for normal operation | B |
| NR | 5 | No damage to device. The output does not regulate and is held low. | B |
| VREF | 6 | Potential device damage due to short circuit current. Not recommended condition. | A |
Table 4-3 Pin FMA for Device Pins Open-Circuited
| Pin Name | Pin No. | Description of Potential Failure Effects | Failure Effect Class |
|---|---|---|---|
| GND | 1 | No damage to device. The output does not regulate and is held low. | B |
| GND | 2 | No damage to device. The output does not regulate and is held low. | B |
| EN | 3 | Normal operation. This pin can be left floating. | D |
| VIN | 4 | Device is unpowered. | B |
| NR | 5 | No damage to device. No impact to functionality. | D |
| VREF | 6 | No damage to device. No impact to functionality. | 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 |
|---|---|---|---|---|
| GND | 1 | GND | Normal Operation. | D |
| GND | 2 | EN | Loss of enable and disable functionslity. The device is in shutdown mode. | B |
| EN | 3 | VIN | Loss of enable and disable functionality. The device is in active mode. | B |
| VIN | 4 | NR | No damage to device. The output does not regulate and follows Vin | B |
| NR | 5 | VREF | No damage to device. NR pin pull more current than expected. Performance degration. | C |
| VREF | 6 | GND | Potential device damage while powering up. Not recommended condition. | A |
Table 4-5 Pin FMA for Device Pins Short-Circuited to supply
| Pin Name | Pin No. | Description of Potential Failure Effects | Failure Effect Class |
|---|---|---|---|
| GND | 1 | The device has no power for normal operation | B |
| GND | 2 | The device has no power for normal operation | B |
| EN | 3 | Loss of enable and disable functionality. | B |
| VIN | 4 | Normal operation. | D |
| NR | 5 | No damage to device. The output does not regulate and follows Vin | B |
| VREF | 6 | Large current can flow into VREF , which can cause permanent damage | A |