SFFS693 September 2023 UCC21551-Q1
4 Pin Failure Mode Analysis (Pin FMA)
This section provides a Failure Mode Analysis (FMA) for the pins of the UCC21551-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 4-5also 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 UCC21551-Q1 pin diagram. For a detailed description of the device pins please refer to the 'Pin Configuration and Functions' section in the UCC21551-Q1 datasheet.
Figure 4-1 Pin DiagramFollowing are the assumptions of use and the device configuration assumed for the pin FMA in this section:
- Pin # 1-8, short to VCCI is considered for Short circuit to supply
- Pin # 14-16, short to VDDA is considered for Short circuit to supply
- Pin # 9-11, short to VDDB is considered for Short circuit to supply
- GND is assumed to be a ground plane on primary side
- Pin # 9-11, short to VSSB is considered for Short circuit to ground
- Pin # 14-16, short to VSSA is considered for Short circuit to ground
- Corner pin adjacent pin short, short to inner pin is considered
- Pin # 11 adjacent pin short to pin#14 is not considered
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 |
|---|---|---|---|
| INA | 1 | OUTA remains low. | B |
| INB | 2 | OUTB remains low. | B |
| VCCI | 3 | Device in reset. No positive power applied to device. | B |
| GND | 4 | No effect. | D |
| EN | 5 | EN function not available. The driver outputs are disabled. | B |
| DT | 6 | No dead time generated. | B |
| NC | 7 | No effect. | D |
| VCCI | 8 | Device in reset. No positive power applied to device. | B |
| VSSB | 9 | No effect. | D |
| OUTB | 10 | OUTB remains low. Possible damage to device. | A |
| VDDB | 11 | OUTB remains low. | B |
| VSSA | 14 | No effect. | D |
| OUTA | 15 | OUTA remains low. Possible damage to device. | A |
| VDDA | 16 | OUTA remains low. | B |
Table 4-3 Pin FMA for Device Pins
Open-Circuited
| Pin Name | Pin No. | Description of Potential Failure Effect(s) | Failure Effect Class |
|---|---|---|---|
| INA | 1 | OUTA remains low. | B |
| INB | 2 | OUTB remains low. | B |
| VCCI | 3 | No effect. | D |
| GND | 4 | Device in reset. OUTA/B do not respond to INA/INB. | B |
| EN | 5 | EN function not available. The OUTA/B are disabled. | B |
| DT | 6 | No dead time generated. | B |
| NC | 7 | No effect. | D |
| VCCI | 8 | No effect. | D |
| VSSB | 9 | OUTB remains unknown. | B |
| OUTB | 10 | OUTB disconnected from the system. | B |
| VDDB | 11 | OUTB remains unknown. | B |
| VSSA | 14 | OUTA remains unknown. | B |
| OUTA | 15 | OUTB disconnected from the system. | B |
| VDDA | 16 | OUTB remains unknown. | B |
Table 4-4 Pin FMA for Device Pins
Short-Circuited to Adjacent Pin
| Pin Name | Pin No. | Shorted to (Pin# + 1) | Description of Potential Failure Effect(s) | Failure Effect Class |
|---|---|---|---|---|
| INA | 1 | INB | INA/INB input level may be unknown. | B |
| INB | 2 | VCCI | OUTB remains high. | B |
| VCCI | 3 | GND | Device in reset. | B |
| GND | 4 | EN | EN function not available. OUTA/B are disabled. | B |
| EN | 5 | DT | No dead time generated. OUTA/B are allowed to turn on simultaneously. | B |
| DT | 6 | NC | No effect. | D |
| NC | 7 | VCCI | No effect. | D |
| VCCI | 8 | N/A | D | |
| VSSB | 9 | OUTB | OUTB remains low. Device may be damaged. | A |
| OUTB | 10 | VDDB | OUTB remains high. Device may be damaged. | A |
| VDDB | 11 | VSSA | N/A | |
| VSSA | 14 | OUTA | OUTA remains low. Device may be damaged. | A |
| OUTA | 15 | VDDA | OUTA remains high. Device may be damaged. | A |
| VDDA | 16 | N/A | 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 |
|---|---|---|---|
| INA | 1 | OUTA remains high. | B |
| INB | 2 | OUTB remains high. | B |
| VCCI | 3 | No effect. | D |
| GND | 4 | Device in reset. | B |
| EN | 5 | No EN function. OUTA and OUTB are enabled. | B |
| DT | 6 | No dead time generated. | B |
| NC | 7 | No effect. | D |
| VCCI | 8 | No effect. | D |
| VSSB | 9 | OUTB remains low. | B |
| OUTB | 10 | OUTB remains high. Device may be damaged. | A |
| VDDB | 11 | No effect. | B |
| VSSA | 14 | OUTA remains low. | B |
| OUTA | 15 | OUTA remains high. Device may be damaged. | A |
| VDDA | 16 | No effect. | D |