SFFS900 June 2024 LM74703-Q1 , LM74704-Q1

4 Pin Failure Mode Analysis (Pin FMA)

This section provides a Failure Mode Analysis (FMA) for the pins of the LM74703-Q1 and LM74704-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 LM74703-Q1 and LM74704-Q1 pin diagram. For a detailed description of the device pins please refer to the Pin Configuration and Functions section in the LM74703-Q1 and LM74704-Q1 data sheet.

Figure 4-1 Pin Diagram

The pin FMA is provided under the assumption that the device is operating under the specified ranges within the Recommended Operating Conditions section of the data sheet.

Table 4-2 Pin FMA for Device Pins Short-Circuited to Ground

Pin Name	Pin No.	Description of Potential Failure Effects	Failure Effect Class
EN	1	Device does not power up External FET can get hot due to Body Diode conduction and be damaged	B
FETGOOD	3	PGOOD cannot assert high in open drain variant ( LM74704-Q1) PGOOD cannot assert high in push-pull variant ( LM74703-Q1) and device Iq increases	B
VCAP+	4	Device can be damaged due to internal paths from ANODE to VCAP External FET can get hot due to Body Diode conduction and be damaged	A
VCAP-	5	Device can be damaged. External FET can get hot due to Body Diode conduction and be damaged	A
ANODE	6	Equivalent to supply short to GND. Device does not power up	B
GATE	7	External FET does not turn ON External FET can get hot due to Body Diode conduction and be damaged Device can be damaged due to diode path between Anode and GATE	A
CATHODE	8	Equivalent to output short to GND Linear regulation and reverse current blocking functionality is lost	B

Table 4-3 Pin FMA for Device Pins Open Circuited

Pin Name	Pin No.	Description of Potential Failure Effects	Failure Effect Class
EN	1	Device is in OFF state due to internal pull down External FET can get hot due to Body Diode conduction and be damaged	B
GND	2	Device does not power up External FET can get hot due to Body Diode conduction and be damaged	B
FETGOOD	3	FETGOOD information is not provided to monitoring system	B
VCAP+	4	External FET does not turn ON External FET can get hot due to Body Diode conduction and be damaged	B
VCAP-	5	External FET does not turn ON External FET can get hot due to Body Diode conduction and be damaged	B
ANODE	6	Device does not power up External FET can get hot due to Body Diode conduction and be damaged	B
GATE	7	External FET does not turn ON External FET can get hot due to Body Diode conduction and be damaged	B
CATHODE	8	The external FET is fully ON, functions as an ON/OFF switch Reverse Current Blocking feature is lost	B

Table 4-4 Pin FMA for Device Pins Short Circuited to Adjacent Pin

Pin Name	Shorted to	Description of Potential Failure Effects	Failure Effect Class
EN	GND	Device does not power up External FET can get hot due to Body Diode conduction and get damaged	B
GND	FETGOOD	PGOOD cannot assert high in open drain variant ( LM74704-Q1) PGOOD cannot assert high in push-pull variant ( LM74703-Q1) and device Iq increases	B
FETGOOD	VCAP+	High current flows in the push-pull variant ( LM74703-Q1) and device can heat up High current flows when FETGOOD pin tries to go low, device can heat up in open drain variant ( LM74704-Q1) In both the variants, VCAP+ collapses when high current flows into PGOOD pin hence GATE can be turned OFF	A
VCAP-	ANODE	No impact	C
ANODE	GATE	External FET does not turn ON External FET can get hot due to Body Diode conduction and be damaged	B
GATE	CATHODE	External FET does not turn ON External FET can get hot due to Body Diode conduction and be damaged	B

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

Pin Name	Pin No.	Description of Potential Failure Effects	Failure Effect Class
EN	1	Device is always on as EN is pulled to supply	B
GND	2	Equivalent to supply short to GND. Device does not power up	B
FETGOOD	3	High current flows in the push-pull variant ( LM74703-Q1) and device can heat up High current flows when PGOOD pin tries to go low, device can heat up in open drain variant ( LM74704-Q1)	A
VCAP+	4	Device cannot turn ON external FET Gate External FET can get hot due to body diode conduction and be damaged	B
VCAP-	5	No impact	C
ANODE	6	No impact	D
GATE	7	External FET does not turn ON External FET can get hot due to body diode conduction and be damaged	B
CATHODE	8	Ideal diode functionality is not available	B