SNVA937A January 2020 – July 2020 TPS2556-Q1 , TPS2557-Q1
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This document contains information for TPS2556-Q1 and TPS2557-Q1 (DRB package) to aid in a functional safety system design. Information provided are:
Figure 1-1 shows the device functional block diagram for reference.
TPS2556-Q1 and TPS2557-Q1 were 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 TPS2556-Q1 and TPS2557-Q1 based on two different industry-wide used reliability standards:
FIT IEC TR 62380 / ISO 26262-11 (1) | FIT (Failures Per 109 Hours) |
---|---|
Total Component FIT Rate | 8 |
Die FIT Rate | 4 |
Package FIT Rate | 4 |
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 | Digital, Analog, Mixed | 20 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 TPS2556-Q1 and TPS2557-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 (%) |
---|---|
OUT no output | 45% |
OUT output not in specification | 40% |
OUT power FET stuck on | 5% |
FAULT false trip or fails to trip | 5% |
Short circuit any two pins | 5% |