SFFS291A October 2021 – September 2022 LM5168 , LM5168-Q1 , LM5169 , LM5169-Q1

4 Pin Failure Mode Analysis (Pin FMA)

This section provides a failure mode analysis (FMA) for the pins of the LM5168-Q1 and LM5169-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 LM5168-Q1 and LM5169-Q1 pin diagram. For a detailed description of the device pins, see the Pin Configuration and Functions section in the LM5168-Q1 and LM5169-Q1 data sheet.

Figure 4-1 Pin Diagram

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

Device used within the Recommended Operating Conditions and the Absolute Maximum Ratings found in the LM5169-Q1/LM5168-Q1 0.65-A/0.3-A, 120-V, Step-Down Converter with Fly-Buck™ Converter Capability Data Sheet
Configuration as shown in the Example Application Circuit found in the LM5169-Q1/LM5168-Q1 0.65-A/0.3-A, 120-V, Step-Down Converter with Fly-Buck™ Converter Capability Data Sheet.
Valid for an ambient temperature of 25ºC.
Faults applied after device start-up is complete.

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
GND	1	Normal operation	D
VIN	2	Input supply shorted to ground. No output voltage	B
EN/UVLO	3	No output voltage. Loss of EN/UVLO functionality	B
RT	4	No or low output voltage	B
FB	5	Output voltage increases to near input voltage level. Possible damage to load	B
PGOOD	6	Normal operation. Loss of PGOOD function	B
BST	7	No output voltage. Possible device damage	A
SW	8	No output voltage. Possible device damage	A

Table 4-3 Pin FMA for Device Pins Open-Circuited

Pin Name	Pin No.	Description of Potential Failure Effect(s)	Failure Effect Class
GND	1	No output voltage	B
VIN	2	No output voltage	B
EN/UVLO	3	No output voltage. Loss of EN/UVLO functionality	B
RT	4	Output voltage out of regulation. Possible damage to load	B
FB	5	Output voltage out of regulation. Possible damage to load	B
PGOOD	6	Normal operation. Loss of PGOOD function	B
BST	7	No output voltage	B
SW	8	No output voltage	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
GND	1	2, VIN	No output voltage. Input supply shorted to ground.	B
VIN	2	3, EN/UVLO	Normal operation. Loss of EN/UVLO functionality	B
EN/UVLO	3	4, RT	No output voltage. Possible device damage	A
FB	5	6, PGOOD	Output voltage out of regulation. Possible damage to load	B
PGOOD	6	7, BST	No output voltage	B
BST	7	8, SW	No output voltage	B

Table 4-5 Pin FMA for Device Pins Short-Circuited to VIN

Pin Name	Pin No.	Description of Potential Failure Effect(s)	Failure Effect Class
GND	1	Input supply shorted. No output voltage	B
VIN	2	Normal operation	D
EN/UVLO	3	Normal operation. EN/UVLO functionality lost	B
RT	4	No output voltage. Device damage	A
FB	5	No output voltage. Device damage	A
PGOOD	6	Loss of PGOOD functionality. Possible device damage	A
BST	7	No output voltage. Device damage	A
SW	8	Output voltage at level of input voltage. Damage to load. Possible device damage	A