SFFS596 april   2023 TLV767-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)

4 Pin Failure Mode Analysis (Pin FMA)

This section provides a failure mode analysis (FMA) for the pins of the TLV767-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 TLV767-Q1 adjustable output pin diagram, and Figure 4-2 shows the TLV767-Q1 fixed output pin diagram. For a detailed description of the device pins, see the Pin Configuration and Functions section in the TLV767-Q1 data sheet.

GUID-20201202-CA0I-3MPZ-TZNQ-KCDLLRCSR4PK-low.svg Figure 4-1 Adjustable Output Pin Diagram
GUID-20201202-CA0I-HL7N-5F5G-MDNVWMPTCF9S-low.svg 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