SFFSAW9A November   2025  – December 2025 LM65680

 

  1.   1
  2.   Trademarks
  3. 1Overview
  4. 2Functional Safety Failure In Time (FIT) Rates
  5. 3Failure Mode Distribution (FMD)
  6. 4Pin Failure Mode Analysis (Pin FMA)
  7. 5Revision History

4 Pin Failure Mode Analysis (Pin FMA)

This section provides a failure mode analysis (FMA) for the pins of the LM65640, LM65660, and LM65680. The failure modes covered in this document include the typical pin-by-pin failure scenarios:

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
ClassFailure Effects
APotential device damage that affects functionality.
BNo device damage, but loss of functionality.
CNo device damage, but performance degradation.
DNo device damage, no impact to functionality or performance.

Figure 4-1 shows the LM65640, LM65660, and LM65680 pin diagram. For a detailed description of the device pins please refer to the Pin Configuration and Functions section in the LM656X0 datasheet.

Figure 4-1 Pin Diagram

Following are the assumptions of use and the device configuration assumed for the pin FMA in this section:

  • The application circuit is configured according to the LM656X0 datasheet.
Table 4-2 Pin FMA for Device Pins Short-Circuited to Ground
Pin NamePin NoDescription of Potential Failure EffectsFailure Effect Class
NC1The device operates as normal.D
11
13
15
20
22
PG 2 There is a loss of Power Good functionality. B
COMP 3 When there is internal compensation, the device operates as normal. D
When there is external compensation, there is a loss of regulation. VOUT = 0V. B
FB4When VOUT is fixed at 3.3V, the FB pin is shorted to ground by default. The device operates as normal.D
When VOUT is fixed at 5V, the VCC pin shorts to ground. There is a loss of regulation. VOUT = 0V.B
When VOUT is adjustable, there is a loss of regulation. VOUT = VIN.B
SS5There is a loss of regulation. VOUT = 0V.B
SGND 6 The device operates as normal. D
CNFG/SYNCOUT 7 There is a loss of regulation. VOUT = 0V. B
MODE/SYNC 8 In AUTO mode, the device operates as normal. D
In FPWM mode, there is a loss of regulation. VOUT = 0V. B
In external SYNC, there is a loss of synchronization. The performance of the device degrades. The device operates in AUTO mode. C
RT 9 When the frequency is fixed at 400kHz, there is a loss of regulation. VOUT = 0V. B
When the frequency is fixed at 2.2MHz, the device operates as normal. D
When the frequency is adjustable, the performance of the device degrades. The device switches at 2.2MHz. C
EN/UVLO 10 The device disables. VOUT = 0V. D
PGND1, PGND212The device operates as normal.D
23
VIN1, VIN214VOUT = 0V.B
21
SW1, SW2, SW316The device is damaged.A
17
18
BST19There is a loss of regulation. VOUT = 0V.B
VCC 24 There is a loss of regulation. VOUT = 0V. B
DRSS/MCOMM 25 The DRSS pin is disabled. Slew rate control is disabled. The performance of EMI degrades. C
BIAS26When the BIAS pin is tied to VOUT, there is a loss of regulation. VOUT = 0V.B
When the BIAS pin is tied to ground, the device operates as normal.D
Table 4-3 Pin FMA for Device Pins Open-Circuited
Pin Name Pin No Description of Potential Failure Effects Failure Effect Class
NC 1 The device operates as normal. D
11
13
15
20
22
PG 2 There is a loss of Power Good functionality. B
COMP 3 When there is internal compensation, the device operates as normal. D
When there is external compensation, the performance of the device degrades. C
FB 4 When VOUT is fixed, there is a loss of regulation. VOUT = 0V. B
When VOUT is adjustable, there is a loss of regulation. VOUT = VIN. B
SS 5 The device operates as normal. D
SGND 6 The performance of the device degrades. C
CNFG/SYNCOUT 7 There is a loss of regulation. VOUT = 0V. B
MODE/SYNC 8 In AUTO mode, the device operates as normal. D
In FPWM mode, the AUTO operation occurs in the next cycle. The performance of the device degrades. C
In external SYNC, there is a loss of synchronization. The device operates in AUTO mode. The performance of the device degrades. C
RT 9 When the frequency is fixed at 400kHz, the performance of the device degrades. The device operates at 2.2MHz. C
When the frequency is fixed at 2.2MHz, the device operates as normal. D
When the frequency is adjustable, the performance of the device degrades. The device operates at 2.2MHz. C
EN/UVLO 10 The device disables. VOUT = 0V. B
PGND1, PGND2 12 The degradation in performance depends on the conditions of the application. C
23
VIN1, VIN2 14 The degradation in performance depends on the conditions of the application. C
21
SW1, SW2, SW3 16 The degradation in performance depends on the conditions of the application. C
17
18
BST 19 There is a loss of regulation. VOUT = 0V. B
VCC 24 The LDO operation is unstable. There is a loss of regulation. B
DRSS/MCOMM 25 The DRSS pin is enabled. The slew rate control is enabled. The device operates as normal. D
BIAS 26 When VOUT is fixed, there is a loss of regulation. VOUT = 0V. B
When VOUT is adjustable, the performance of the device degrades. The IQ is higher. C
Table 4-4 Pin FMA for Device Pins Short-Circuited to Adjacent Pin
Pin Name Adjacent Pin Description of Potential Failure Effects Failure Effect Class
NC PG The device operates as normal. D
PG COMP When there is internal compensation, there is a loss of PG functionality. B
When there is external compensation, there is a loss of regulation. B
COMP FB When there is external compensation, and VOUT is fixed at 3.3V, there is a loss of regulation. VOUT = 0. B
When there is external compensation, and VOUT is fixed at 5V, there is a loss of regulation. There is an overvoltage condition. B
When there is external compensation, and VOUT is adjustable, there is a loss of regulation. There is an overvoltage condition. B
FB SS When VOUT is fixed at 3.3V, there is a loss of regulation. VOUT = 0. B
When VOUT is fixed at 5V, there is a loss of regulation. VOUT = 0. B
When VOUT is adjustable, there is a loss of regulation. B
SS SGND There is a loss of regulation. VOUT = 0V. B
SGND CNFG/SYNCOUT There is a loss of regulation. VOUT = 0V. B
CNFG/SYNCOUT MODE/SYNC When there is internal compensation (COMP pin tied to VCC), the device operates in FPWM mode. D
When there is external compensation (COMP pin pulled to GND with a 49.9kΩ resistor), the device operates in AUTO mode. D
MODE/SYNC RT The RT pin is tied to GND and the MODE pin is tied to GND. The device operates as normal. D
The RT pin is tied to GND and the MODE pin is tied to VCC. There is a loss of regulation. VOUT = 0. B
The RT pin is tied to VCC and the MODE pin is tied to GND. There is a loss of regulation. VOUT = 0. B
The RT pin is tied to VCC and the MODE pin is tied to VCC. The device operates as normal. D
The RT pin is pulled to GND with a resistor and the MODE pin is tied to GND. There is a loss of regulation. B
The RT pin is pulled to GND with a resistor and the MODE pin is tied to VCC. There is a loss of regulation. B
RT EN/UVLO The RT pin is tied to GND and the EN pin is tied to VIN. There is a loss of regulation. VOUT = 0. B
The RT pin is tied to VCC and the EN pin is tied to VIN. The device is damaged. A
The RT pin is pulled to GND with a resistor and the EN pin is tied to VIN. The performance of the device degrades. C
EN/UVLO NC The device operates as normal. D
NC PGND1 The device operates as normal. D
PGND1 NC The device operates as normal. D
NC VIN1 The device operates as normal. D
VIN1 NC The device operates as normal. D
NC SW1 The device operates as normal. D
SW1 SW2 The device operates as normal. D
SW2 SW3 The device operates as normal. D
SW3 BST The device operates as normal. B
BST NC The device operates as normal. D
NC VIN2 The device operates as normal. D
VIN2 NC The device operates as normal. D
NC PGND2 The device operates as normal. D
PGND2 VCC There is a loss of regulation. VOUT = 0V. B
VCC DRSS/MCOMM The DRSS pin is tied to VCC. The device operates as normal. D
The DRSS pin is tied to GND. There is a loss of regulation. VOUT = 0V. B
The DRSS pin is pulled to GND with a resistor. The performance of the device degrades. C
DRSS/MCOMM BIAS The DRSS pin is tied to GND and the BIAS pin is tied to GND. The device operates as normal. D
The DRSS pin is tied to VCC and the BIAS pin is tied to GND. There is a loss of regulation. VOUT = 0V. B
The DRSS pin is pulled to GND with a resistor and the BIAS pin is tied to GND. The performance of the device degrades. C
The DRSS pin is tied to GND and the BIAS pin is tied to VOUT. There is a loss of regulation. B
The DRSS pin is tied to VCC and the BIAS pin is tied to VOUT (<5V). The device operates as normal. D
The DRSS pin is tied to VCC and the BIAS pin is tied to VOUT (>5V). The device is damaged. A
The DRSS pin is pulled to GND with a resistor and the BIAS pin is tied to VOUT. The performance of the device degrades. C
BIAS NC The device operates as normal. D
Table 4-5 Pin FMA for Device Pins Short-Circuited to Supply
Pin Name Pin No Description of Potential Failure Effects Failure Effect Class
NC 1 The device operates as normal. D
11
13
15
20
22
PG 2 The device is damaged if supply > Absolute Maximum Rating. A
COMP 3 The device is damaged if supply > 5.5V. A
FB 4 The device is damaged if supply > 5.5V. A
SS 5 The device is damaged if supply > 5.5V. A
SGND 6 VOUT = 0V. B
CNFG/SYNCOUT 7 The device is damaged if supply > 5.5V. A
MODE/SYNC 8 The device is damaged if supply > 5.5V. A
RT 9 The switching frequency is undefined. The performance of the device degrades. C
EN/UVLO 10 The device operates as normal. D
PGND1, PGND2 12 VOUT = 0V. B
23
VIN1, VIN2 14 The device operates as normal. D
21
SW1, SW2, SW3 16 The device is damage. A
17
18
BST 19 The device is damage. A
VCC 24 The device is damaged if supply > 5.5V. A
DRSS/MCOMM 25 The device is damaged if supply > Absolute Maximum Rating. A
BIAS 26 The device is damaged if supply > Absolute Maximum Rating. A