SFFS117 March 2021 TMCS1108-Q1
4 Pin Failure Mode Analysis (Pin FMA)
This section provides a Failure Mode Analysis (FMA) for the pins of the TMCS1108-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 TMCS1108-Q1 pin diagram. For a detailed description of the device pins please refer to the Pin Configuration and Functions section in the TMCS1108-Q1 data sheet.
Figure 4-1 TMCS1108-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=-600V to 600V
- VREF=0V to VS
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 |
|---|---|---|---|
| IN+ | 1 | For forward current, hall-sensor bypassed, providing no signal to be sensed and amplified. If IN+ is at a large potential above GND, this will result in a lot of current being sunk. Depending upon layout and configuration, this could damage the input current system supply, the load device, or the TMCS1100. | A |
| IN+ | 2 | For forward current, hall-sensor bypassed, providing no signal to be sensed and amplified. If IN+ is at a large potential above GND, this will result in a lot of current being sunk. Depending upon layout and configuration, this could damage the input current system supply, the load device, or the TMCS1100. | A |
| IN- | 3 | For reverse current, hall-sensor bypassed, providing no signal to be sensed and amplified. If IN- is at a large potential above GND, this will result in a lot of current being sunk. Depending upon layout and configuration, this could damage the input current system supply, the load device, or the TMCS1100. | A |
| IN- | 4 | For reverse current, hall-sensor bypassed, providing no signal to be sensed and amplified. If IN- is at a large potential above GND, this will result in a lot of current being sunk. Depending upon layout and configuration, this could damage the input current system supply, the load device, or the TMCS1100. | A |
| GND | 5 | Normal Operation | D |
| NC | 6 | Datasheet recommended connection. | D |
| VOUT | 7 | 'Output will be pulled to GND and output current will be short circuit limited. When left in this configuration while VS connected to a high load capable supply and for certain high load conditions through the IN+ and IN- pins, die temperature could approach or exceed 150°C. | B |
| VS | 8 | Power supply shorted to ground | B |
Table 4-3 Pin FMA for Device Pins
Open-Circuited
| Pin Name | Pin No. | Description of Potential Failure Effect(s) | Failure Effect Class |
|---|---|---|---|
| IN+ | 1 | If left open and pin 2 is connected, pin 2 could suffer thermal stress for currents approaching SOA boundary ratings. For normal operating conditions, sensitivity error may increase. | A |
| IN+ | 2 | If left open and pin 1 is connected, pin 1 could suffer thermal stress for currents approaching SOA boundary ratings. For normal operating conditions, sensitivity error may increase. | A |
| IN- | 3 | If left open and pin 4 is connected, pin 4 could suffer thermal stress for currents approaching SOA boundary ratings. For normal operating conditions, sensitivity error may increase. | A |
| IN- | 4 | If left open and pin 3 is connected, pin 3 could suffer thermal stress for currents approaching SOA boundary ratings. For normal operating conditions, sensitivity error may increase. | A |
| GND | 5 | GND is floating. Output will be incorrect as it is no longer referenced to GND. | B |
| NC | 6 | Normal Operation. | D |
| VOUT | 7 | Output will be present at the pin; having no loading will not affect the output. However, the user will see unpredictable results further down on the signal chain. | B |
| VS | 8 | No power to device. VOUT will stay at GND. | B |
Table 4-4 Pin FMA for Device Pins
Short-Circuited to Adjacent Pin
| Pin Name | Pin No. | Shorted to | Description of Potential Failure Effect(s) | Failure Effect Class |
|---|---|---|---|---|
| IN+ | 1 | 2 - IN+ | Normal Operation. | D |
| IN+ | 2 | 3 - IN- | IN+ shorted to IN-. This creates a current divider which increase sensitivity error inversely proportional to the resistance of the short. | C |
| IN- | 3 | 4 - IN- | Normal Operation. | D |
| IN- | 4 | 5 - GND | For reverse current, hall-sensor bypassed, providing no signal to be sensed and amplified. If IN- is at a large potential above GND, this will result in a lot of current being sunk. Depending upon layout and configuration, this could damage the input current system supply, the load device, or the TMCS1100. | A |
| GND | 5 | 6 - NC | Datasheet recommended connection. | D |
| NC | 6 | 7 - VOUT | Neither damages device or degrade performance so long as NC not already shorted to GND or VS. If NC shorted to VS or GND, output will be pulled to VS or GND and output current will be short circuit limited. When left in this configuration while VS connected to a high load capable supply and for certain high load conditions through the IN+ and IN- pins, die temperature could approach or exceed 150°C. | B if NC = GND or NC = VS, D otherwise |
| VOUT | 7 | 8 - VS | Output will be pulled to VS and output current will be short circuit limited. When left in this configuration while VS connected to a high load capable supply and for certain high load conditions through the IN+ and IN- pins, die temperature could approach or exceed 150°C. | B |
| VS | 8 | 1 - IN+ | If 6V>IN+ > 5.5V, device will be operating in non-linear range. If IN+>6V, the device will be damaged. If IN+ < Vs, a lot of current may be pulled from the stage supplying the TMCS1100 | A |
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 |
|---|---|---|---|
| IN+ | 1 | If 6V>IN+ > 5.5V, device will be operating in non-linear range. If IN+>6V, the device will be damaged. If IN+ < Vs, a lot of current may be pulled from the stage supplying the TMCS1100. | A |
| IN+ | 2 | If 6V>IN+ > 5.5V, device will be operating in non-linear range. If IN+>6V, the device will be damaged. If IN+ < Vs, a lot of current may be pulled from the stage supplying the TMCS1100. | A |
| IN- | 3 | If 6V>IN- > 5.5V, device will be operating in non-linear range. If IN->6V, the device will be damaged. If IN- < Vs, a lot of current may be pulled from the stage supplying the TMCS1100. | A |
| IN- | 4 | If 6V>IN- > 5.5V, device will be operating in non-linear range. If IN->6V, the device will be damaged. If IN- < Vs, a lot of current may be pulled from the stage supplying the TMCS1100. | A |
| GND | 5 | Output shorts to supply. Stage supplying the TMCS1100 will pull a lot of current | B |
| NC | 6 | Pin can tolerate either resistive or capacitive connection to Vs | D |
| VOUT | 7 | Output will be pulled to VS and output current will be short circuit limited. When left in this configuration while VS connected to a high load capable supply and for certain high load conditions through the IN+ and IN- pins, die temperature could approach or exceed 150°C. | B |
| VS | 8 | Normal operation | D |