SFFS743 November 2023 TPS3840
4 Pin Failure Mode Analysis (Pin FMA)
This section provides a failure mode analysis (FMA) for the pins of the TPS3840. 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 TPS3840 pin diagram. For a detailed description of the device pins, see the Pin Configuration and Functions section in the TPS3840 data sheet.
Figure 4-1 Pin DiagramFollowing are the assumptions of use and the device configuration assumed for the pin FMA in this section:
- Vdd(min) < Vdd < Vdd (max) assumption
- Reset is connected to VDD with 10.5-kΩ pull-up resistor
Table 4-2 Pin FMA for Device Pins
Short-Circuited to Ground
| Pin Name | Pin No. | Description of Potential Failure Effects | Failure Effect Class |
|---|---|---|---|
| RESET | 1 | Forces RESET to be held low. | B |
| VDD | 2 | VDD short to GND Fault. The device is non-operational. | B |
| GND | 3 | No damage to device. No impact to functionality. | D |
| MR / NC | 4 | Normal operation. RESET will be asserted. | B |
| CT | 5 | RESET is forced and held low when VDD goes below threshold. Device is non-operational. | B |
Table 4-3 Pin FMA for Device Pins Open-Circuited
| Pin Name | Pin No. | Description of Potential Failure Effects | Failure Effect Class |
|---|---|---|---|
| RESET | 1 | Unreliable reset output functionality. | B |
| VDD | 2 | The device is unpowered and non-operational. | B |
| GND | 3 | The RESET and VDD are both held low. | B |
| MR / NC | 4 | Normal Operation. This pin can be left floating. | D |
| CT | 5 | Normal Operation. This pin can be left floating. | 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 |
|---|---|---|---|---|
| RESET | 1 | VDD | Large current can flow into RESET when in error condition. This can cause permanent damage. | A |
| VDD | 2 | GND | The device is non-operational. | B |
| GND | 3 | MR / NC | Normal operation. RESET will be asserted. | B |
| MR / NC | 4 | CT | RESET is forced and held low when VDD goes below threshold. Device is non-operational. | B |
| CT | 5 | RESET | RESET is forced and held low when VDD goes below threshold. Device is non-operational. | B |
Table 4-5 Pin FMA for Device Pins Short-Circuited to supply
| Pin Name | Pin No. | Description of Potential Failure Effects | Failure Effect Class |
|---|---|---|---|
| RESET | 1 | Large current can flow into RESET when in error condition. This can cause permanent damage. | A |
| VDD | 2 | Normal operation. | D |
| GND | 3 | VDD short to GND fault. Device is non-operational. | B |
| MR / NC | 4 | Normal operation. | D |
| CT | 5 | Forces RESET to be held low. Device is non-operational. | B |