SNVAA03 December   2020 LM76005

 

  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 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.

GUID-5D89FA11-5E36-4507-B068-74FAB3B55A42-low.gif 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