SFFS420 April   2022 LM5141

 

  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 LM5141. 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 LM5141 pin diagram. For a detailed description of the device pins, please refer to the Pin Configuration and Functions section in the LM5141 data sheet.

Figure 4-1 Pin Diagram

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

  • Application circuit as per LM5141 data sheet is used
  • PG is pulled up to VOUT
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
DEMB 1 VOUT = expected, DEMB mode only, and no synchronization is available. C
If DEMB = VDDA, VOUT = 0 V. Loaded VCC output B
VDDA 2 VOUT = 0 V. No switching. Loaded VCC output B
AGND 3 AGND is GND. VOUT = expected D
RT 4 Normal operation. VOUT = expected. FSW defaults to 2.2 MHz or 440 kHz, depending on OSC. C
DITH 5 Dither disabled. VOUT = expected C
OSC 6 If OSC = GND, then FSW = 440 kHz. VOUT = expected C
If OSC = VDDA, then VOUT = 0 V. Loaded VCC output
LOL 7 VOUT = 0 V. The VCC regulator is loaded to current limit. B
LO 8 VOUT = 0 V. The VCC regulator is loaded to current limit. B
PGND 9 PGND is GND. VOUT = expected D
VCC 10 VOUT = 0 V. The VCC regulator is loaded to current limit. B
HB 11 VOUT = 0 V. The VCC regulator is loaded to current limit. B
SW 12 VOUT = 0 V. Excessive current from VIN B
HO 13 VOUT = 0 V. High-side MOSFET cannot be turned on. B
HOL 14 VOUT = 0 V. High-side MOSFET cannot be turned on. B
VIN 15 VOUT = 0 V B
VCCX 16 VOUT = expected. The internal VCC regulator provides bias voltage. C
VOUT 17 VOUT = 0 V. Current limit reached and hiccup mode occurs. B
CS 18 VOUT = 0 V B
FB 19 If FB = VDDA, then VOUT = 0 V. D
If FB = GND, then VOUT = 5 V. B
COMP 20 VOUT = 0 V B
PG 21 VPG = 0 V. VOUT = expected C
SS 22 VOUT = 0 V C
EN 23 VOUT = 0 V. The LM5141 is disabled and enters shutdown. C
RES 24 VOUT = expected. The LM5141 cannot exit hiccup mode. C
Table 4-3 Pin FMA for Device Pins Open-Circuited
Pin Name Pin No. Description of Potential Failure Effect(s) Failure Effect Class
DEMB 1 Diode emulation/FPWM mode undefined. VOUT = expected, erratic switching C
VDDA 2 VOUT = 0 V. Poor noise immunity C
AGND 3 VOUT = 0 V B
RT 4 Normal operation. Frequency modulation feature is disabled. VOUT = expected C
DITH 5 VOUT = expected C
OSC 6 FSW 440 kHz or 2.2 MHz. VOUT = expected C
LOL 7 VOUT = 0 V. No discharge path for low-side MOSFET gate B
LO 8 VOUT = expected. Lower efficiency C
PGND 9 VOUT = 0 V. Uncontrolled behavior because of floating ground B
VCC 10 VOUT = 0 V B
HB 11 VOUT = 0 V. High-side gate drive floating B
SW 12 VOUT = VIN. High-side FET control floating B
HO 13 VOUT = 0 V. Will not regulate B
HOL 14 VOUT = VIN. Will not regulate. Excessive current from VIN B
VIN 15 VOUT = 0 V B
VCCX 16 VOUT = expected D
VOUT 17 VOUT = oscillation. Will not regulate B
CS 18 VOUT = oscillation. No overcurrent or current sense information for current mode control. B
FB 19 VOUT will not regulate. The controller will be configured for adjustable output. B
COMP 20 VOUT = oscillation. Will not regulate B
PG 21 VOUT = expected. No PG information C
SS 22 VOUT = expected D
EN 23 VOUT = 0 V B
RES 24 VOUT = expected. Will exit hiccup mode quickly because low parasitic capacitor value. C
Table 4-4 Pin FMA for Device Pins Short-Circuited to Adjacent Pin
Pin Name Pin No. Shorted To Description of Potential Failure Effect(s) Failure Effect Class
DEMB 1 VDDA VOUT = regulation, normal operation, and FPWM mode is enabled. C
VDDA 2 AGND VOUT = 0 V B
AGND 3 RT VOUT = regulation. Frequency modulation is disabled. C
RT 4 DITH VOUT = regulation. Frequency modulation is disabled. C
DITH 5 OSC VOUT = regulation. FSW = 440 kHz C
OSC 6 LOL VOUT = unregulated B
LOL 7 LO VOUT = expected C
LO 8 PGND VOUT = 0 V B
PGND 9 VCC VOUT = 0 V B
VCC 10 HB VOUT = 0 V B
HB 11 SW VOUT = 0 V. The VCC regulator is in current limit. B
SW 12 HO VOUT = 0 V B
HO 13 HOL VOUT = expected B
HOL 14 VIN VOUT = 0 V A
VIN 15 VCCX If VVIN > 6.5 V, then VOUT = 0 V. Exceeds the VCCX absolute maximum ratings A
VCCX 16 VOUT VOUT = expected D
If VOUT is > 6.5 V, then it exceeds the VCCX absolute maximum rating. A
VOUT 17 CS VOUT cannot regulate, current limit is disabled, and there is no current sense information. B
CS 18 FB If FB = VDDA, then VOUT = 3.3 V. B
If FB = GND, then VOUT = 0 V. Excessive current from VIN B
FB 19 COMP If FB = VDDA, then VOUT = VIN. A
If FB = GND, then VOUT = 0 V. B
COMP 20 PG VOUT = 0 V B
PG 21 SS VOUT = 0 V B
SS 22 EN If VEN > 6.5 V, then it will exceed the absolute maximum rating of the SS pin. VOUT = 0 V A
EN 23 RES If VEN > 6.5 V, then it will exceed the absolute maximum rating of the SS pin. VOUT = 0 V A
RES 24 DEMB If DEMB = GND, VOUT = regulation, then it will not restart if current limit is reached. B
If DEMB = VDDA, then VOUT = regulation. No hiccup mode B
Table 4-5 Pin FMA for Device Pins Short-Circuited to VIN
Pin Name Pin No. Description of Potential Failure Effect(s) Failure Effect Class
DEMB 1 If DEMB = GND, then VOUT = 0 V. Excessive current for VIN B
If DEMB = VDDA and VVIN < 6.5 V, then VOUT = expected and there is erratic switching. B
If VVIN > 6.5 V and exceeds the maximum rating of the DEMP pin, the device is damaged. A
VDDA 2 If VVIN > 6.5 V, VOUT = 0 V, and exceeds the maximum rating of the VDDA pin, the device is damaged. A
If VVIN < 6.5 V, then VOUT = expected. D
AGND 3 High VIN current. VOUT = 0 V B
RT 4 If VVIN < 6.5 V, then VOUT = 0 V. B
If VVIN > 6.5 V and exceeds the maximum ratings, then the device is damaged. A
DITH 5 If VVIN > 6.5 V, the device is damaged. A
If VVIN < 6.5 V, OUT = expected. No spread spectrum C
OSC 6 If OSC = GND and high VIN current, then VOUT = 0 V. B
If OSC = VDDA, VIN > 6.5 V, the device is damaged, and VOUT = 0 V. A
If OSC = VDDA, VIN < 6.5 V, VOUT = expected, and there is erratic switching. C
LOL 7 If VVIN < 6.5 V, VOUT = 0 V and there is excessive current from VIN. B
If VVIN > 6.5 V, exceeds the maximum ratings for the LO pin and the device is damaged. A
LO 8 If VVIN < 6.5 V, VOUT = 0 V and there is excessive current from VIN. B
If VVIN > 6.5 V, exceeds the maximum ratings for the LOL pin, the device is damaged A
PGND 9 VOUT = 0 V. Excessive current from VIN B
VCC 10 If VVIN < 6.5 V, then VOUT = expected. D
If VVIN > 6.5 V, exceeds the maximum ratings and the device is damaged. A
HB 11 If VVIN < 6.5 V, then VOUT = expected and there is erratic switching. B
If VVIN > 6.5 V, exceeds the maximum rating the device is damaged and VOUT = VIN. A
SW 12 VOUT = VIN. Excessive current from VIN A
HO 13 If VVIN < 6.5 V, VOUT drops lower than VIN, no switching, and excessive current from VIN. B
If VVIN > 6.5 V, exceeds maximum ratings of the HO pin, the device is damaged, and VOUT = VIN. A
HOL 14 If VVIN < 6.5 V, VOUT drops lower than VIN, no switching, and excessive current from VIN. B
If VVIN > 6.5 V, exceeds maximum ratings of the HO pin, the device is damaged, and VOUT = VIN.
VIN 15 N/A B
VCCX 16 For VCCX = VOUT, VIN < 6.5 V and VOUT = VIN. B
If VVIN > 6.5 V, it exceeds the VCCX pin maximum rated voltage and the LM5141 is damaged. A
VOUT 17 If VVIN < 15.5 V, VOUT = VIN. B
If VVIN > 15.5 V and exceeds the maximum rating, the LM5141 is damaged. A
CS VVIN < 6.5 V. VOUT = VIN B
If VVIN > 15.5 V and exceeds the maximum rating, the LM5141 is damaged. A
FB 19 If VVIN < 6.5 V, FB = VDDA, then VOUT = expected. B
If VVIN < 6.5 V, FB = GND, then VOUT = 0 V. Excessive current from VIN B
If VVIN > 6.5 V and exceeds the maximum ratings, the LM5141 is damaged. A
COMP 20 If VVIN > 5 V and < 6.5 V, VOUT = 0 V B
If VVIN > 6.5 V and exceeds the maximum ratings, the LM5141 is damaged. A
PG 21 If VVIN < 6.5 V, VOUT = expected and PG forced high. B
If VVIN > 6.5 V and exceeds the maximum ratings, the LM5141 is damaged. A
SS 22 If VVIN < 6.5 V, then VOUT = expected. D
If VVIN > 6.5 V and exceeds the maximum ratings, the LM5141 is damaged. A
EN 23 VOUT = expected D
RES 24 If VVIN < 6.5 V, VOUT = expected. No hiccup mode C
If VVIN > 6.5 V and exceeds the maximum ratings, the LM5141 is damaged. A