SFFS534 October 2022 TPSM365R3 , TPSM365R6

4 Pin Failure Mode Analysis (Pin FMA)

This section provides a Failure Mode Analysis (FMA) for the pins of the TPSM365R6 and TPSM365R3. 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 TPSM365R6 and TPSM365R3 pin diagram. For a detailed description of the device pins please refer to the Pin Configuration and Functions section in the TPSM365R6 and TPSM365R3 data sheet.

1. See the data sheet for more details. Pin 1 trimmed and factory-set for externally adjustable switching frequency RT variants only.

2. Pin 11 factory-set for fixed switching frequency MODE/SYNC variants only.

3. Pin 9 trimmed and factory-set for fixed output voltage VOUT/BIAS variants only.

4. Pin 9 factory-set for adjustable output voltage FB variants only.

Figure 4-1 Pin Diagram

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
PGOOD	1	When not in use, this pin can be left open or grounded. However, PGOOD is no longer reliably relays Power-Good information to devices connected to this pin.	B
EN	2	VOUT = 0 V, device is disabled.	B
VIN	3	VOUT = 0 V.	B
VOUT	4	Goes into hiccup, short-circuit operation.	B
SW	5, 6	Damage occurs.	A
BOOT	7	VOUT = 0 V, HS FET does not turn on.	B
VCC	8	VOUT = 0 V.	B
VOUT/BIAS or FB	9	VOUT = 0 V.	B
GND	10	Normal operation.	D
RT or MODE	11	For RT, the switching frequency is set to 2.2 MHz. For MODE/SYNC the device goes into PFM mode.	B

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

Pin Name	Pin No.	Description of Potential Failure Effect(s)	Failure Effect Class
PGOOD	1	When not in use, this pin can be left open or grounded. However, PGOOD is no longer reliably relays Power-Good information to devices connected to this pin.	B
EN	2	VOUT behavior is not defined. VOUT may be 0V, but it also may be up. Do not float this pin. Device can no longer reliably be enabled or disabled by other devices connected to this pin.	B
VIN	3	VOUT = 0 V.	B
VOUT	4	VOUT = 0 V.	B
SW	5, 6	Normal operation.	D
BOOT	7	Normal operation.	D
VCC	8	VCC output is unstable, can increase above 5.5 V	A
FB	9	VOUT = 0 V. Do not float this pin.	B
GND	10	VOUT can be abnormal, as reference voltage is not fixed.	B
RT or MODE	11	If it is RT device, then frequency is not defined. If it is a MODE/SYNC device, then the device can go back and forth between FPWM and PFM. VOUT is up, but only partially functional.	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
PGOOD	1	EN	If EN > 20 V, it damages devices connected to the PGOOD pin.	A
EN	2	VIN	VOUT normal (enable is on, all other blocks work). However, the device can no longer be disabled.	B
VIN	3	VOUT	If VIN >16 V, damage occurs.	A
VOUT	4	SW	Damage occurs.	A
SW	6	BOOT	VOUT = 0 V, HS does not turn on, no Cboot.	B
BOOT	7	VCC	Damage occurs to VCC LDO. The VCC LDO could no longer supply voltage to internal control circuits.	A
VCC	8	FB	Can be partially nonfunctional, no damage occurs.	B
FB	9	GND	VOUT = 0 V (for fixed option) switches at maximum duty cycle for ADJ option.	B
GND	10	RT or MODE	For RT, Switching Frequency is set to 2.2 MHz. For MODE/SYNC the device goes into PFM mode.	B
RT or MODE	11	PGOOD	If PGOOD is high and < 5.5 V, then Fsw = 1 MHz for RT, and is in FPWM mode for MODE/SYNC; If PGOOD is low, then Fsw = 2.2 MHz for RT, and PFM mode for RT. PGOOD absmax being 20 V, RT ESD damages if PG goes to 20 V.	A

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
PGOOD	1	If VIN > 20 V, it damages PGOOD. PGOOD is no longer reliably relays Power-Good information to devices connected to this pin.	A
EN	2	VOUT normal (enable is on, all other blocks work). However, the device can no longer be disabled.	B
VIN	3	Normal operation.	D
VOUT	4	Damage occurs, if VIN > 16 V.	A
SW	5, 6	Damage occurs.	A
BOOT	7	Damage occurs, the BOOT ESD clamp is damaged.	A
VCC	8	If Vin > 5.5 V, damage occurs.	A
FB	9	If VIN > 20 V, damage occurs.	A
GND	10	VOUT = 0 V.	A
RT	11	If Vin > 5.5 V, damage occurs. If Vin < 5.5 V, switching frequency is 1 MHz.	A