4 Pin Failure Mode Analysis (Pin FMA)

This section provides a failure mode analysis (FMA) for the pins of the LM5152-Q1 and LM51521-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 LM5152-Q1 and LM51521-Q1 pin diagram. For a detailed description of the device pins, see the Pin Configuration and Functions section in the LM5152-Q1 and LM51521-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 Operation Conditions and the Absolute Maximum Ratings found in the LM5152x-Q1 Automotive Low-IQ Synchronous Boost Controller for Start-Stop data sheet.
For the analysis, the typical application as shown in the Typical Application section of the LM5152x-Q1 Automotive Low-IQ Synchronous Boost Controller for Start-Stop data sheet is used.
V_supply = V_bias = 12 V
V_OUT = 16 V

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
CSP	1	The CSP pin can be damaged if the differential voltage exceeds the 0.3-V absolute maximum rating.	A
CSN	2	The CSN pin can be damaged if the differential voltage exceeds the 0.3-V absolute maximum rating.	A
VOUT/SENSE	3	VOUT is out of regulation. Possible overcharge of the output voltage	A
STATUS	4	Correct output voltage, but loss of STATUS functionality	B
HO	5	High-side driver can be damaged when SW voltage rises.	A
SW	6	No energy is transferred from input to output.	B
HB	7	The HB pin can be damaged when SW voltage rises.	A
BIAS	8	The device is unpowered and, therefore, not functional.	B
VCC	9	Loss of VCC regulation and there is no switching.	B
PGND	10	No effect	D
LO	11	VOUT is out of regulation. LO stops switching.	B
MODE	12	Diode emulation mode is activated. No effect in case the device is configured for diode emulation mode (MODE = GND).	C
UVLO/EN	13	The device is disabled.	B
SYNC/DITHER/VH/CP	14	External clock synchronization is disabled. Spread spectrum is disabled. VCC is not held when EN = GND and the high-side switch cannot turn on 100% during bypass operation. No effect in case external clock synchronization and spread spectrum are disabled and the VCC hold function and high-side switch turn on 100% in bypass mode function is disabled (SYNC/DITHER/VH/CP = GND).	C
RT	15	Maximum switching frequency is much greater than 2.21 MHz.	C
VREF/RANGE	16	No switching. Target output voltage is 0 V.	B
SS	17	Device does not start and there is no switching.	B
TRK	18	VOUT out of regulation and there is no switching.	B
AGND	19	No effect	D
COMP	20	VOUT out of regulation and is not switching.	B

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

Pin Name	Pin No.	Description of Potential Failure Effect(s)	Failure Effect Class
CSP	1	Loss of current sense signal	B
CSN	2	Loss of current sense signal	B
VOUT/SENSE	3	VOUT out of regulation and there is a possible overcharge of the output voltage.	A
STATUS	4	Correct output voltage, but loss of STATUS functionality	B
HO	5	Loss of the high-side driver. Operating with sync FET body diode conducting	C
SW	6	Loss of the high-side driver. Operating with sync FET body diode conducting	C
HB	7	Loss of boot voltage and hence, the high-side driver. Operating with sync FET body diode conducting	C
BIAS	8	Device is unpowered and, therefore, not functional.	B
VCC	9	No stable VCC to sustain normal operation	B
PGND	10	Possible device damage	A
LO	11	Low-side MOSFET is never switched.	B
MODE	12	No effect if skip mode is active, otherwise skip mode is activated.	C
UVLO/EN	13	Device is disabled.	B
SYNC/DITHER/VH/CP	14	Loss of holdup functionality and charge-pump functionality	C
RT	15	Minimum frequency is set.	C
VREF/RANGE	16	VOUT is out of regulation.	B
SS	17	Small soft-start time. Normal operation after start-up	C
TRK	18	VOUT out of regulation	B
AGND	19	Possible device damage	A
COMP	20	Device can be unstable.	C

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
CSP	1	CSN	Loss of current sense information. Circuit can be unstable.	C
CSN	2	VOUT/SENSE	Possible damage. Exceeds absolute maximum voltage rating	A
VOUT/SENSE	3	PGOOD	Loss of VOUT feedback. Possibly unstable operation	B
STATUS	4	HO	No damage and loss of STATUS function	B
HO	5	SW	Loss of the high-side driver. Operating with sync FET body diode conducting	B
SW	6	HB	Loss of boot voltage and hence, the high-side driver. Operating with sync FET body diode conducting	B
HB	7	BIAS	Possible damage. HB exceeds the absolute maximum voltage rating.	A
BIAS	8	VCC	Possible damage to VCC if BIAS is above the absolute maximum voltage rating of VCC, otherwise no damage.	A
VCC	9	PGND	No VCC rail and there is no switching.	B
PGND	10	LO	LO never turns on. Switching never happens.	B
LO	11	MODE	Switching mode toggles with every switching cycle.	C
MODE	12	UVLO/EN	Switching mode is set by the UVLO/EN pin voltage.	B
UVLO/EN	13	SYNC/DITHER/VH/CP	SYNC/DITHER/VH/CP setting set by the UVLO/EN pin.	B
SYNC/DITHER/VH/CP	14	RT	Possible damage. Can exceed the RT absolute maximum voltage	A
RT	15	VREF/RANGE	Switching frequency will not be correct.	C
VREF/RANGE	16	SS	Small soft-start time	C
SS	17	TRK	TRK > 1.2 V stops any switching on the controller.	B
TRK	18	AGND	VOUT is out of regulation and there is no switching.	B
AGND	19	COMP	VOUT is out of regulation and is not switching.	B
COMP	20	CSP	Possible damage. Exceeds absolute maximum voltage rating of COMP.	A

Table 4-5 Pin FMA for Device Pins Short-Circuited to 12-V Supply

Pin Name	Pin No.	Description of Potential Failure Effect(s)	Failure Effect Class
CSP	1	Normal operation	D
CSN	2	Loss of current sense signal. Circuit can be unstable.	C
VOUT/SENSE	3	VOUT is out of regulation.	B
STATUS	4	Loss of STATUS functionality	B
HO	5	The HO pin can exceed the HO to SW absolute maximum voltage rating.	A
SW	6	No energy is transferred from input to output.	B
HB	7	HB exceeds HB to SW absolute maximum voltage rating.	A
BIAS	8	Normal operation	D
VCC	9	VCC exceeds absolute maximum voltage rating.	A
PGND	10	Possible damage	A
LO	11	Possible damage. Exceeds absolute maximum voltage rating	A
MODE	12	Possible damage. Exceeds absolute maximum voltage rating	A
UVLO/EN	13	No UVLO functionality	C
SYNC/DITHER/VH/CP	14	Possible damage. Exceeds absolute maximum voltage rating	A
RT	15	Possible damage. Exceeds absolute maximum voltage rating	A
VREF/RANGE	16	Possible damage. Exceeds absolute maximum voltage rating	A
SS	17	Possible damage. Exceeds absolute maximum voltage rating	A
TRK	18	Possible damage. Exceeds absolute maximum voltage rating	A
AGND	19	Possible damage. Exceeds absolute maximum voltage rating	A
COMP	20	Possible damage. Exceeds absolute maximum voltage rating	A