This document contains information for TPS61379-Q1 (VQFN package) to aid in a functional safety system design. Information provided are:
Figure 1-1 shows the device functional block diagram for reference.
TPS61379-Q1 was developed using a quality-managed development process, but were not developed in accordance with the IEC 61508 or ISO 26262 standards.
This section provides Functional Safety Failure In Time (FIT) rates for TPS61379-Q1 based on two different industry-wide used reliability standards:
FIT IEC TR 62380 / ISO 26262 | FIT (Failures Per 109 Hours) |
---|---|
Total Component FIT Rate | 14 |
Die FIT Rate | 7 |
Package FIT Rate | 7 |
The failure rate and mission profile information in Table 2-1 comes from the Reliability data handbook IEC TR 62380 / ISO 26262 part 11:
Table | Category | Reference FIT Rate | Reference Virtual TJ |
---|---|---|---|
5 | CMOS, BICMOS ASICs Analog & Mixed <= 50V supply | 25 FIT | 55°C |
The Reference FIT Rate and Reference Virtual TJ (junction temperature) in Table 2-2 come from the Siemens Norm SN 29500-2 tables 1 through 5. Failure rates under operating conditions are calculated from the reference failure rate and virtual junction temperature using conversion information in SN 29500-2 section 4.
The failure mode distribution estimation for TPS61379-Q1 in Table 3-1 comes from the combination of common failure modes listed in standards such as IEC 61508 and ISO 26262, the ratio of sub-circuit function size and complexity and from best engineering judgment.
The failure modes listed in this section reflect random failure events and do not include failures due to misuse or overstress.
Die Failure Modes | Failure Mode Distribution (%) |
---|---|
VO No output GND or HiZ | 50% |
VO output not in specification voltage or timing | 40% |
Load disconnect stuck on | 5% |
PG false trip, fails to trip | 5% |
This section provides a Failure Mode Analysis (FMA) for the pins of the TPS61379-Q1. 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.
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 TPS61379-Q1 pin diagram. For a detailed description of the device pins please refer to the 'Pin Configuration and Functions' section in the TPS61379-Q1 data sheet.
Following are the assumptions of use and the device configuration assumed for the pin FMA in this section:
Pin Name | Pin No. | Description of Potential Failure Effects(s) | Failure Effect Class |
---|---|---|---|
VIN | 1 | The device does not operate. Power supply is short. | B |
BST | 2 | Possible device damage | A |
SW | 3 | Potential damage to inductor and pin | A |
SW | 4 | Potential damage to inductor and pin | A |
MODE/SYNC | 5 | The device remains in Auto PFM mode. Loss of forced PWM mode, spread spectrum functionality, and frequency synchronization functionality | C |
VCC | 6 | Output voltage out of regulation | B |
GND | 7 | No effect | D |
GND | 8 | No effect | D |
VO | 9 | The device remains in hiccup output short circuit protection mode. | B |
OUT | 10 | Potential damage to device | A |
PG | 11 | Correct output voltage. Loss of PG functionality | C |
NC | 12 | No effect | D |
FB | 13 | Output voltage is regulated to 5 V. | B |
COMP | 14 | No output voltage | B |
EN | 15 | Loss of ENABLE functionality. The device remains in Shut Down mode. | B |
FREQ | 16 | Switching frequency is 2 MHz typically. | C |
Pin Name | Pin No. | Description of Potential Failure Effects(s) | Failure Effect Class |
---|---|---|---|
VIN | 1 | The device does not work. Output voltage is 0 V. | B |
BST | 2 | The device is damaged. | A |
SW | 3 | Possible device damage | A |
SW | 4 | Possible device damage | A |
MODE/SYNC | 5 | Device remains in auto PFM mode. Loss of Forced PWM mode, spread spectrum functionality, and frequency synchronization functionality | C |
VCC | 6 | High ripple on VCC pin. Efficiency is lower. | C |
GND | 7 | Possible device damage | A |
GND | 8 | Possible device damage | A |
VO | 9 | No output voltage | B |
OUT | 10 | Possible device damage | A |
PG | 11 | Correct output voltage. Loss of PG functionality | C |
NC | 12 | No effect | D |
FB | 13 | Output voltage is out of regulation. | B |
COMP | 14 | Output voltage is out of regulation. | B |
EN | 15 | Loss of ENABLE functionality. The device remains in Shut Down mode. | B |
FREQ | 16 | No output voltage | B |
Pin Name | Pin No. | Shorted to | Description of Potential Failure Effects(s) | Failure Effect Class |
---|---|---|---|---|
VIN | 1 | BST | Possible device damage | A |
BST | 2 | SW | Output voltage out of regulation | B |
SW | 3 | SW | No effect | D |
SW | 4 | MODE/SYNC | Possible device damage | A |
MODE/SYNC | 5 | VCC | The device remains in forced PWM mode. Loss of Auto PFM mode and frequency synchronization functionality | C |
VCC | 6 | GND | The device does not work. VOUT = 0 V | B |
GND | 7 | GND | No effect | D |
GND | 8 | VO | The device remains in hiccup output short circuit protection mode. | B |
VO | 9 | OUT | Loss of Down mode functionality and hiccup output short circuit protection | B |
OUT | 10 | PG | Possible device damage | A |
PG | 11 | NC | Potential device damage if PG is pulled up to higher than 6 V. | A |
NC | 12 | FB | No effect | D |
FB | 13 | COMP | No output voltage | B |
COMP | 14 | EN | OVP is triggered | B |
EN | 15 | FREQ | No output voltage | B |
FREQ | 16 | VIN | The FREQ pin is damaged if supply voltage is higher than 6 V. | A |
Pin Name | Pin No. | Description of Potential Failure Effects(s) | Failure Effect Class |
---|---|---|---|
VIN | 1 | No effect | D |
BST | 2 | Possible device damage | A |
SW | 3 | Damage to internal power FETs | A |
SW | 4 | Damage to internal power FETs | A |
MODE/SYNC | 5 | The MODE/SYNC pin damaged if supply voltage is higher than 6 V. | A |
VCC | 6 | VCC pin is damaged if supply voltage is higher than 6 V. | A |
GND | 7 | Possible device damage due to large current | A |
GND | 8 | Possible device damage due to large current | A |
VO | 9 | VO = VIN | B |
OUT | 10 | The device remains in Hiccup mode. No output voltage | B |
PG | 11 | Possible device damage | A |
NC | 12 | The NC pin is damaged if supply voltage is higher than 6 V. | A |
FB | 13 | The FB pin is damaged if supply voltage is higher than 6 V. | A |
COMP | 14 | The COMP pin is damaged if supply voltage is higher than 6 V. | A |
EN | 15 | The EN pin is damaged if supply voltage is higher than 6 V. | A |
FREQ | 16 | The FREQ pin is damaged if supply voltage is higher than 6 V. | A |