SFFS182 June 2021 LM5146

4 Pin Failure Mode Analysis (Pin FMA)

This section provides a Failure Mode Analysis (FMA) for the pins of the LM5146. 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 short-circuited to 12 V (see Table 4-3)
Pin open-circuited (see Table 4-5)
Pin short-circuited to an adjacent pin (see Table 4-6)

Table 4-2 through Table 4-6 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 LM5146 pin diagram. For a detailed description of the device pins please refer to the Pin Configuration and Functions section in the LM5146 data sheet.

Figure 4-1 Pin Diagram

Table 4-2 Pin FMA for Short to GND

Pin Name	Pin No.	Description of Potential Failure Effect(s)	Failure Effect Class
EN/UVLO	1	VOUT = 0 V	B
RT	2	VOUT = 0 V	B
SS/TRK	3	VOUT = 0 V	B
COMP	4	VOUT = 0 V	B
FB	5	VOUT is limited by when the part enters into hiccup mode	B
AGND	6	Normal operation	D
SYNCOUT	7	VOUT = 0 V	B
SYNCIN	8	Normal operation with DCM at light loads	B
NC9	9	Normal operation	D
PGOOD	10	Normal operation	C
ILIM	11	Normal operation	B
PGND	12	Normal operation	D
LO	13	VOUT = 0 V	B
VCC	14	VOUT = 0 V	B
EP	15	Normal operation	D
NC16	16	Normal operation	D
BST	17	VOUT = 0 V	B
HO	18	VOUT = 0 V	B
SW	19	VOUT = 0 V	A
VIN	20	VOUT = 0 V	B

Table 4-3 Pin FMA for Short to VIN ≥ 12 V

Pin Name	Pin No.	Description of Potential Failure Effect(s)	Failure Effect Class
EN/UVLO	1	ESD protection runs full current and RT pin destroyed (VOUT = 0 V)	C
RT	2	ESD protection runs full current and SS pin destroyed (VOUT = 0 V)	A
SS/TRK	3	ESD protection runs full current and COMP destroyed (VOUT = 0 V)	A
COMP	4	ESD protection runs full current and COMP pin destroyed (VOUT = 0 V)	A
FB	5	ESD protection runs full current and FB pin destroyed (VOUT = 0 V)	A
AGND	6	VOUT = 0 V	D
SYNCOUT	7	ESD protection runs full current and SYNCOUT pin destroyed (VOUT = 0 V)	A
SYNCIN	8	ESD protection runs full current and SYNCIN pin destroyed, but the part continues to work normally	A
NC9	9	Normal operation	D
PGOOD	10	ESD protection runs full current and PGOOD pin destroyed, but VOUT might not be affected	A
ILIM	11	Buck operation is not affected	C
PGND	12	VOUT = 0 V	B
LO	13	VOUT = 0 V	B
VCC	14	ESD protection runs full current and VCC pin destroyed (VOUT = 0 V)	A
EP	15	Normal operation	D
NC16	16	Normal operation	D
BST	17	ESD protection runs full current and BST pin destroyed (VOUT = 0 V)	A
HO	18	VOUT = VIN	A
SW	19	VOUT = VIN	B
VIN	20	Normal operation	D

Table 4-4 Pin FMA for Short to VOUT

Pin Name	Pin Number	Description of Potential Failure Effect(s)	Failure Class
EN/UVLO	1	VOUT = 0 V	B
RT	2	VOUT = 0 V	A
SS/TRK	3	VOUT = 0 V	A
COMP	4	VOUT = 0 V	A
FB	5	VOUT = VREF	A
AGND	6	VOUT = 0 V	B
SYNCOUT	7	Normal operation	A
SYNCIN	8	Normal operation. FPWM enabled	A
NC9	9	Normal operation	D
PGOOD	10	Normal operation	A
ILIM	11	Normal operation	C
PGND	12	VOUT = 0 V	B
LO	13	VOUT = 0 V	B
VCC	14	VOUT = 0 V	A
EP	15	Normal operation	D
NC16	16	Normal operation	D
BST	17	VOUT = 0 V	B
HO	18	VOUT = 0 V	B
SW	19	VOUT = 0 V	B
VIN	20	VOUT = VIN	B

Table 4-5 Pin FMA Open-Circuited

Pin Name	Pin Number	Description of Potential Failure Effect(s)	Failure Class
EN/UVLO	1	VOUT = 0 V	B
RT	2	VOUT = 0 V	B
SS/TRK	3	Normal operation	C
COMP	4	Regulated to required voltage. SW freq is all over the place	B
FB	5	VOUT = 0 V	B
AGND	6	VOUT = 0 V	B
SYNCOUT	7	Normal operation	C
SYNCIN	8	Normal operation. DCM mode	C
NC9	9	Normal operation	D
PGOOD	10	Normal operation	C
ILIM	11	Normal operation	C
PGND	12	VOUT = 0 V	B
LO	13	Normal operation. DCM mode enabled at light loads	B
VCC	14	VOUT = 0 V	B
EP	15	Normal operation	D
NC16	16	Normal operation	D
BST	17	VOUT = 0 V	B
HO	18	VOUT = 0 V	B
SW	19	VOUT = 0 V	B
VIN	20	VOUT = 0 V	B

Table 4-6 Pin FMA for Short-Circuited to Adjacent Pin

Pin Name	Pin Number	Description of Potential Failure Effect(s)	Failure Class	Neighbor
EN/UVLO	1	Normal operation	C	VIN
RT	2	VOUT = 0 V	B	SS/TRK
SS/TRK	3	VOUT = 0 V	B	COMP
COMP	4	VOUT is not regulated to required voltage and is controlled by the ON time it makes when COMP is 0.8 V and the switching frequency set by RT pin	B	FB
FB	5	VOUT is limited by when the part enters into hiccup mode	B	AGND
AGND	6	VOUT = 0 V	B	SYNCOUT
SYNCOUT	7	Normal operation	C	SYNCIN
SYNCIN	8	Normal operation	D	NC9
NC9	9	Normal operation	D
PGOOD	10	Normal operation	A	ILIM
ILIM	11	Normal operation	D
PGND	12	VOUT = 0 V	A	LO
LO	13	VOUT = 0 V	B	VCC
VCC	14	Normal operation	D	EP
EP	15	Normal operation	D	NC16
NC16	16	Normal operation	D	BST
BST	17	VOUT = 0 V	B	HO
HO	18	VOUT = 0 V	B	SW
SW	19	Normal operation	D
VIN	20	Normal operation	D