SNVAA03 December 2020 LM76005

4 Pin Failure Mode Analysis (Pin FMA)

This section provides a Failure Mode Analysis (FMA) for the pins of the LM76005. 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 LM76005 pin diagram. For a detailed description of the device pins please refer to the Pin Configuration and Functions section in the LM76005 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 LM76005 data sheet.
Configuration as shown in the 'Example Application Circuit' found in the LM76005 data sheet.

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
SW	1, 2, 3, 4, 5	Damage to internal power FETs	A
BOOT	6	Damage to internal circuits	A
N/C	7	None functional pin, no connection	D
VCC	8	Fault mode will shut the device down.	B
BIAS	9	Normal operation	D
RT	10	Set to frequency much higher than 500 KHz and can cause damge to internal circuit.	B
SS/TRK	11	Set output to zero voltage.	B
FB	12	Shorting FB will cause no voltage regulation control.	B
AGND	13, 14, 15	Normal operation	D
PGOOD	16	PGOOD not valid signal, VOUT in regulation	D
SYNC/MODE	17	Shorted to GND is DCM/PFM operation	C
EN	18	Vout = 0 V	B
NC	19	None functional pin, no connection	D
PVIN	20, 21, 22	Device will not operate.	B
N/C	23	None functional pin, no connection	D
PGND	24, 25, 26	Normal operation	D
N/C	27, 28, 29, 30	None functional pin, no connection	D

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

Pin Name	Pin No.	Description of Potential Failure Effect(s)	Failure Effect Class
SW	1, 2, 3, 4, 5	Loss of output voltage regulation	B
BOOT	6	Loss of output voltage regulation	B
N/C	7	None functional pin, no connection	D
VCC	8	VCC will be unstable and cause damage to internal circuits.	A
BIAS	9	Normal operation	D
RT	10	Set to default frequency 400 KHz.	C
SS/TRK	11	Use the 6.3-ms internal soft-start ramp.	D
FB	12	Floating FB will cause no voltage regulation control.	B
AGND	13, 14, 15	Can cause damage to internal circuits	A
PGOOD	16	PGOOD not valid signal, VOUT in regulation	D
SYNC/MODE	17	Floating this pin can cause unexpected operation mode.	B
EN	18	Device may not power up.	B
NC	19	None functional pin, no connection	D
PVIN	20, 21, 22	Device can become damaged if only one PVIN pin is connected to PCB board.	A
N/C	23	None functional pin, no connection	D
PGND	24, 25, 26	Device can become damaged if only one PGND pin is connected to PCB board.	A
N/C	27, 28, 29, 30	None functional pin, no connection	D

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

Pin Name	Pin No.	Description of Potential Failure Effect(s)	Failure Effect Class
SW	1, 2, 3, 4	SW pin 1 to pin 5 are expected to be shorted.	D
SW	5	Loss of output voltage regulation, possible damage internal circuits	A
BOOT	6	Normal operation	D
N/C	7	None functional pin, no connection	D
VCC	8	VCC will be unstable if BIAS voltage is noisy or cause damage if BIAS >5.5 V.	A
BIAS	9	Switching frequency set to near 0 Hz or damage to internal circuits > 5 V	A
RT	10	Switching frequency set to near 0 Hz.	B
SS/TRK	11	Switching frequency set to near 0 Hz.	B
FB	12	Shorting FB will cause no voltage regulation control.	B
AGND	13	Shorting FB will cause no voltage regulation control.	B
AGND	14, 15	Normal operation	D
PGOOD	16	Can cause damage to internal circuits	A
SYNC/MODE	17	If voltage exceeds 5.5 V, damage to internal circuits will happen.	A
EN	18	Normal operation	D
NC	19	None functional pin, no connection	D
PVIN	20, 21, 22	No impact	D
N/C	23	None functional pin, no connection	D
PGND	24, 25, 26	Device is operational.	D
N/C	27, 28, 29, 30	None functional pin, no connection	D

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
SW	1, 2, 3, 4, 5	Damage to LS FET	A
BOOT	6	Damage to internal circuits	A
N/C	7	None functional pin, no connection	D
VCC	8	Damage if voltage exceeds 5.5 V	A
BIAS	9	Damage to internal circuits if voltage exceeds 30 V	A
RT	10	If voltage exceeds 5.5 V, damage to internal circuits will happen.	A
SS/TRK	11	If voltage exceeds 5 V, damage to internal circuits will happen.	A
FB	12	If voltage exceeds 5 V, damage to internal circuits will happen.	A
AGND	13, 14, 15	Can cause damage to internal circuits	A
PGOOD	16	Can cause damage to internal circuits if voltage exceeds 20 V	A
SYNC/MODE	17	If voltage exceeds 5.5 V, damage to internal circuits will happen.	A
EN	18	EN pin can handle ≤ 60 V. Greater than 60 V can cause damage to internal circuits.	D
NC	19	None functional pin, no connection	D
PVIN	20, 21, 22	Normal operation	D
N/C	23	None functional pin, no connection	D
PGND	24, 25, 26	Can cause damage to internal circuits or package	A
N/C	27, 28, 29, 30	None functional pin, no connection	D