SFFS842A March 2024 – May 2025 TMCS1123-Q1 , TMCS1126-Q1 , TMCS1127-Q1 , TMCS1133-Q1
4.2 TMCS1126-Q1 Pin FMA
This section provides a failure mode analysis (FMA) for the pins of the TMCS1126-Q1. The failure modes covered in this document include the typical pin-by-pin failure scenarios:
- Pin short-circuited to ground (see Table 4-14)
- Pin open-circuited (see Table 4-15)
- Pin short-circuited to an adjacent pin (see Table 4-16)
- Pin short-circuited to supply (see Table 4-17)
Table 4-14 through Table 4-17 also indicate how these pin conditions can affect the device as per the failure effects classification in Table 4-1.
Figure 4-2 shows the TMCS1126-Q1 pin diagram. For a detailed description of the device pins please refer to the Pin Configuration and Functions section in the TMCS1126-Q1 data sheet.
Figure 4-2
TMCS1126-Q1 Pin DiagramFollowing are the assumptions of use and the device configuration assumed for the pin FMA in this section:
- TA = -40°C to +125°C
- VS = 3V to 5.5V
- VCM = -1.3kV to 1.3kV
Table 4-6 Pin FMA for Device Pins
Short-Circuited to Ground
| Pin Name | Pin No. | Description of Potential Failure Effects | Failure Effect Class |
|---|---|---|---|
| IN+ | 1 | For forward current, hall-sensor bypassed, providing no signal to be sensed and amplified. If the IN+ pin is at a large potential above GND, this state results in a large amount of current being sunk. Depending upon layout and configuration, this result can damage the input current system supply, the load device, or the actual device. | A |
| IN- | 2 | For reverse current, hall-sensor bypassed, providing no signal to be sensed and amplified. If the IN- pin is at a large potential above GND, this state results in a large amount of current being sunk. Depending upon layout and configuration, this result can damage the input current system supply, the load device, or the actual device. | A |
| OC | 3 | Alert is not able to trigger since OC is shorted to GND. | B |
| VS | 4 | Power supply is shorted to ground. | B |
| VOC | 5 | Threshold at GND means that all voltages trip the alert. As a result, the alert is stuck in active mode. | B |
| VOUT | 6 | Output pulled to GND and output current are short circuit limited. When left in this configuration, while VS is connected to a high-load-capable supply and for certain high-load conditions through the IN+ and IN- pins, the die temperature can potentially approach or exceed 150°C. | A |
| VREF | 7 | VREF is shorted to GND and the output current is short circuit limited. | B |
| NC | 8 | Normal operation. | D |
| GND | 9 | Normal operation. | D |
| NC | 10 | Normal operation. | D |
Table 4-7 Pin FMA for Device Pins
Open-Circuited
| Pin Name | Pin No. | Description of Potential Failure Effects | Failure Effect Class |
|---|---|---|---|
| IN+ | 1 | No current running through inputs. | B |
| IN- | 2 | No current running through inputs. | B |
| OC | 3 | Alert open; cannot read alert. | B |
| VS | 4 | No power to device. VOUT stays close to GND. | B |
| VOC | 5 | No alert threshold is set. Alert output is unpredictable. | B |
| VOUT | 6 | Output is present at the pin, having no loading does not affect the output. However, the user sees unpredictable results further down on the signal chain. | B |
| VREF | 7 | VREF is present at the pin, no loading does not affect the device. However, the user sees unpredictable results further down on the signal chain. | B |
| NC | 8 | Normal operation. | D |
| GND | 9 | GND is floating. Output is incorrect as the output is no longer referenced to GND. | B |
| NC | 10 | Normal operation. | D |
Table 4-8 Pin FMA for Device Pins
Short-Circuited to Adjacent Pin
| Pin Name | Pin No. | Shorted to | Description of Potential Failure Effects | Failure Effect Class |
|---|---|---|---|---|
| IN+ | 1 | IN- | IN+ is shorted to IN-. This creates a current divider which increases sensitivity error inversely proportional to the resistance of the short. | C |
| IN- | 2 | OC | IN- is shorted to OC. If IN- > 6V, the device is damaged. If IN- < OC, large current can be pulled from VS. | A |
| OC | 3 | VS | OC is shorted to VS. Large current can be pulled from VS. | A |
| VS | 4 | VOC | VOC is shorted to VS, overcurrent threshold is at the wrong threshold. | B |
| VOC | 5 | VOUT | VOC is shorted to VOUT. Overcurrent threshold varies, alert response is unpredictable. | B |
| VOUT | 6 | VREF | Output is shorted to VREF. Based on the voltage level of each, the output current can potentially be short circuit limited. When left in this configuration, while VS is connected to a high-load-capable supply and for certain high-load conditions through the IN+ and IN- pins, the die temperature can approach or exceed 150°C. | A |
| VREF | 7 | NC | Normal operation. | D |
| NC | 8 | GND | Normal operation. | D |
| GND | 9 | NC | Normal operation. | D |
| NC | 10 | IN+ | If IN+ > 6V, the device can be damaged. If NC is at VS and IN+ < Vs, or if NC is at GND and IN+ is at a large potential above ground, large current can be flowing between VS and the input current system supply. | A if IN+ > 6V |
| B otherwise |
Table 4-9 Pin FMA for Device Pins
Short-Circuited to
Supply
| Pin Name | Pin No. | Description of Potential Failure Effects | Failure Effect Class |
|---|---|---|---|
| IN+ | 1 | If IN+ > 6V, the device is damaged. If IN+ < Vs, a large amount of current can be pulled from VS. | A |
| IN- | 2 | If IN- > 6V, the device is damaged. If IN- < Vs, a large amount of current can be pulled from VS. | A |
| OC | 3 | OC pin stuck high, potentially has too high of a current draw when triggered. | B |
| VS | 4 | Normal operation. | D |
| VOC | 5 | Overcurrent threshold at the wrong threshold. | B |
| VOUT | 6 | Output pulled to VS and output current is short circuit limited. When left in this configuration, while VS is connected to a high-load-capable VS and for certain high-load conditions through the IN+ and IN- pins, the die temperature can approach or exceed 150°C. | A |
| VREF | 7 | VREF is shorted to VS and the output current is short circuit limited. | B |
| NC | 8 | Normal operation. | D |
| GND | 9 | VS is shorted to GND. | B |
| NC | 10 | Normal operation. | D |