SFFS379A September   2022  – March 2023 TLV766-Q1

 

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

Pin Failure Mode Analysis (Pin FMA)

This section provides a failure mode analysis (FMA) for the pins of the TLV766-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.

#GUID-59B67224-3CC4-4810-AE39-411866CAB6F7 shows the TLV766-Q1 adjustable output pin diagram, and #FIG_AML_4HY_KSB shows the TLV766-Q1 fixed output pin diagram. For a detailed description of the device pins, see the Pin Configuration and Functions section in the TLV766-Q1 data sheet.

Figure 4-1 Adjustable Output Pin Diagram
Figure 4-2 Fixed Output Pin Diagram
Table 4-2 Pin FMA for Device Pins Short-Circuited to Ground
Pin Name Pin No. Description of Potential Failure Effects Failure Effect Class
OUT 1 Regulation is not possible. The device operates at current limit and can cycle in and out of thermal shutdown. B
NC 2 No effect. Normal operation. D
FB/SNS 3

(Fixed output.) Regulation is not possible. The device operates at current limit and can cycle in and out of thermal shutdown.

(Adjustable output.) The device operates as a switch because the gate of the pass transistor is driven fully on.

B/B
GND 4 No effect. Normal operation. D
EN 5 The device is disabled, resulting in no output voltage. B
GND 6 No effect. Normal operation. D
NC 7 No effect. Normal operation. D
IN 8 No power to the device, resulting in no output voltage. B
Table 4-3 Pin FMA for Device Pins Open-Circuited
Pin Name Pin No. Description of Potential Failure Effects Failure Effect Class
OUT 1 The device output is disconnected from the load. B
NC 2 No effect. Normal operation. D
FB/SNS 3

(Fixed output.) The output voltage is incorrect.

(Adjustable output.) The error amplifier input is not connected. The output voltage is indeterminate.

B/B
GND 4 There is no current loop for the supply voltage. The device is not operational and does not regulate. B
EN 5 The enable circuit is in an unknown state. The device is either enabled or disabled. B
GND 6 A very small possibility exists that device turns on even if EN is held low. B
NC 7 No effect. Normal operation. D
IN 8 No power is supplied to the device, resulting in no output voltage. B
Table 4-4 Pin FMA for Device Pins Short-Circuited to Adjacent Pin
Pin Name Pin No. Shorted to Description of Potential Failure Effects Failure Effect Class
OUT 1 NC (pin 2) No effect. Normal operation. D
NC 2 FB/SNS (pin 3) No effect. Normal operation. D
FB/SNS 3 GND (pin 4)

(Fixed output.) Regulation is not possible. The device operates at current limit and can cycle in and out of thermal shutdown.

(Adjustable output.) The device operates as a switch because the gate of the pass transistor is driven fully on.

B/B
EN 5 GND (pin 6) The device is disabled, resulting in no output voltage. B
GND 6 NC (pin 7) No effect. Normal operation. D
NC 7 IN (pin 8) No effect. Normal operation. D
Table 4-5 Pin FMA for Device Pins Short-Circuited to VIN
Pin Name Pin No. Description of Potential Failure Effects Failure Effect Class
OUT 1

(Fixed output.) Regulation is not possible because VOUT = VIN, but no damage occurs because OUT and SNS can handle up to VIN + 0.3 V (max).

(Adjustable output.) If FB is tied to OUT, damage is possible on FB. See the Absolute Maximum Ratings table in the product data sheet. If the device is configured with a resistive feedback network, no damage occurs.

B/A
NC 2 No effect. Normal operation. D
FB/SNS 3

(Fixed output.) Regulation is not possible because VOUT = VIN.

(Adjustable output.) If VIN is greater than 3 V, the rating for FB (3 V max) is violated and can damage the device. If VIN is less than 3 V and if there is any loading on the device, the output is approximately 0 V.

A/B
GND 4 No output voltage. System performance depends on upstream current limiting. B
EN 5 The device is always enabled when the input is powered. B
GND 6 No output voltage. System performance depends on upstream current limiting. B
NC 7 No effect. Normal operation. D
IN 8 No effect. Normal operation. D