SFFS842 March 2024 TMCS1126-Q1

4 Pin Failure Mode Analysis (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 4-2)
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 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 4-1 TMCS1126-Q1 Pin Diagram

Following are the assumptions of use and the device configuration assumed for the pin FMA in this section:

T_A= -40°C to +125°C
V_S= 3V to 5.5V
V_CM= -1.3kV to 1.3kV
VREF = 0V to V_S

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 IC itself.	A
IN-	2	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 IC itself.	A
OC	3	The Alert will not be able to trigger since it would be shorted to GND.	B
VS	4	Power supply shorted to ground.	B
VOC	5	Threshold at GND means that all voltages trip the Alert, so the Alert would be stuck in active mode.	B
VOUT	6	Output 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.	A
VREF	7	VREF shorted to GND and output current will be short circuit limited.	B
NC	8	Normal Operation.	D
GND	9	Normal Operation.	D
NC	10	Normal Operation.	D

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	No current running through inputs.	B
IN-	2	No current running through inputs.	B
OC	3	Alert open, won't be able to read alert.	B
VS	4	No power to device. Vout will stay close to GND.	B
VOC	5	No alert threshold set, alert output will be unpredictable.	B
VOUT	6	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
VREF	7	VREF will be present at the pin; having no loading will not affect the device. However, the user will see unpredictable results further down on the signal chain.	B
NC	8	Normal Operation.	D
GND	9	GND is floating. Output will be incorrect as it is no longer referenced to GND.	B
NC	10	Normal Operation.	D

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	IN-	IN+ shorted to IN-. This creates a current divider which increase sensitivity error inversely proportional to the resistance of the short.	C
IN-	2	OC	IN- shorted to OC. If IN->6V, the device will be damaged. If IN- < OC, Large current may be pulled from VS.	A
OC	3	VS	OC shorted to VS. Large current may be pulled from VS.	A
VS	4	VOC	VOC shorted to VS, over current threshold will be at the wrong threshold.	B
VOC	5	VOUT	VOC shorted to VOUT. Over current threshold will vary, alert response will be unpredictable.	B
VOUT	6	VREF	Output shorted to VREF. Based on the voltage level of each, the output current may 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.	A
VREF	7	NC	VREF either left open, or shorted to VS or GND depending on NC pin connection.	D if NC is open, B otherwise
NC	8	GND	If NC at GND or open, then normal operation. If NC at VS, then VS shorted to GND.	B if NC is at VS, D otherwise
GND	9	NC	If NC at GND or open, then normal operation. If NC at VS, then VS shorted to GND.	B if NC is at VS, D otherwise
NC	10	IN+	If IN+> 6V, the device may 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 may be flowing between VS and the input current system supply.	A if IN+>6V; B otherwise

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 IN+>6V, the device will be damaged. If IN+ < Vs, a lot of current may be pulled from VS.	A
IN-	2	If IN->6V, the device will be damaged. If IN- < Vs, a lot of current may be pulled from VS.	A
OC	3	OC pin stuck high, may have too high current draw when triggered.	B
VS	4	Normal operation.	D
VOC	5	Over current threshold at the wrong threshold.	B
VOUT	6	Output pulled to VS and output current will be short circuit limited. When left in this configuration while VS connected to a high load capable VS and for certain high load conditions through the IN+ and IN- pins, die temperature could approach or exceed 150°C.	A
VREF	7	VREF pulled to VS and output current will be short circuit limited.	B
NC	8	Normal operation.	D
GND	9	VS shorted to GND.	B
NC	10	Normal operation.	D