DRV8703-Q1Functional Safety FIT Rate, FMD and Pin FMA

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1 Overview

This document contains information for DRV8703-Q1 (VQFN (32) package) to aid in a functional safety system design. Information provided are:

Functional Safety Failure In Time (FIT) rates of the semiconductor component estimated by the application of industry reliability standards
Component failure modes and their distribution (FMD) based on the primary function of the device
Pin failure mode analysis (Pin FMA)

DRV8703-Q1 was developed using a quality-managed development process, but was not developed in accordance with the IEC 61508 or ISO 26262 standards.

Figure 1-1 shows the device functional block diagram for reference.

Figure 1-1 Functional Block Diagram

2 Functional Safety Failure In Time (FIT) Rates

This section provides Functional Safety Failure In Time (FIT) rates for DRV8703-Q1 based on two different industry-wide used reliability standards:

Table 2-1 provides FIT rates based on IEC TR 62380 / ISO 26262 part 11
Table 2-2 provides FIT rates based on the Siemens Norm SN 29500-2

Table 2-1 Component Failure Rates per IEC TR 62380 / ISO 26262 Part 11

FIT IEC TR 62380 / ISO 26262	FIT (Failures Per 10⁹ Hours)
Total Component FIT Rate	20
Die FIT Rate	3
Package FIT Rate	17

The failure rate and mission profile information in Table 2-1 comes from the Reliability data handbook IEC TR 62380 / ISO 26262 part 11:

Mission Profile: Motor Control from Table 11
Power dissipation: 250 mW
Climate type: World-wide Table 8
Package factor (lambda 3): Table 17b
Substrate Material: FR4
EOS FIT rate assumed: 0 FIT

Table 2-2 Component Failure Rates per Siemens Norm SN 29500-2

Table	Category	Reference FIT Rate	Reference Virtual T_J
5	CMOS, BICMOS, Digital, analog/mixed	25 FIT	55 °C

The Reference FIT Rate and Reference Virtual T_J (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.

3 Failure Mode Distribution (FMD)

The failure mode distribution estimation for DRV8703-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.

Table 3-1 Die Failure Modes and Distribution

Die Failure Modes	Failure Mode Distribution (%)
Low side gate turned ON, when commanded OFF	20.5%
Low side gate turned OFF, when commanded ON	16.0%
Low side gate to source voltage too high or too low	0.5%
Low side gate driver slew rate too fast or too slow	2.5%
High side gate turned ON, when commanded OFF	20.5%
High side gate turned OFF, when commanded ON	15.0%
High side gate to source voltage too high or too low	0.5%
High side gate driver slew rate too fast or too slow	3.5%
Dead time between high side FET and low side FET transition incorrect	1.0%
Current sense feedback and regulation incorrect	6.0%
Drain Source voltage monitoring incorrect	4.0%
Incorrect communication or fault indication	10.0%

The FMD in Table 3-1 excludes short circuit faults across the isolation barrier. Faults for short circuit across the isolation barrier can be excluded according to ISO 61800-5-2:2016 if the following requirements are fulfilled:

The signal isolation component is OVC III according to IEC 61800-5-1. If a SELV/PELV power supply is used, pollution degree 2/OVC II applies. All requirements of IEC 61800-5-1:2007, 4.3.6 apply.
Measures are taken to ensure that an internal failure of the signal isolation component cannot result in excessive temperature of its insulating material.

Creepage and clearance requirements should be applied according to the specific equipment isolation standards of an application. Care should be taken to maintain the creepage and clearance distance of a board design to ensure that the mounting pads of the isolator on the printed-circuit board do not reduce this distance.