SNVAA02 December   2020 LM76005-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)

Pin Failure Mode Analysis (Pin FMA)

This section provides a Failure Mode Analysis (FMA) for the pins of the LM76005-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 LM76005-Q1 pin diagram. For a detailed description of the device pins please refer to the Pin Configuration and Functions section in the LM76005-Q1 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-Q1 data sheet.
  • Configuration as shown in the 'Example Application Circuit' found in the LM76005-Q1 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