DRV8912-Q1Functional Safety FIT Rate, FMD and Pin FMA

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1 Overview

This document contains information for the DRV8912-Q1 (HTSSOP 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)

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

Figure 1-1 Functional Block Diagram

The DRV8912-Q1 was developed using a quality-managed development process, but was not developed in accordance with the IEC 61508 or ISO 26262 standards.

2 Functional Safety Failure In Time (FIT) Rates

This section provides functional safety failure in time (FIT) rates for the DRV8912-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	23
Die FIT rate	7
Package FIT rate	16

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: 1150 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, or 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 the DRV8912-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 resulting from misuse or overstress.

Table 3-1 Die Failure Modes and Distribution

Die Failure Modes	Failure Mode Distribution (%)
Output is stuck LOW when commanded OFF (GND short)	11%⁽¹⁾
Output is stuck HIGH when commanded OFF (VM short)	11%⁽¹⁾
Output is stuck OFF when commanded LOW (Open)	14%⁽¹⁾
Output is stuck OFF when commanded HIGH (Open)	14%⁽¹⁾
Output ON resistance too high when commanded LOW	11%⁽¹⁾
Output ON resistance too high when commanded HIGH	11%⁽¹⁾
Low side slew rate too fast or too slow (high-side recirculation)	5%⁽¹⁾
High side slew rate too fast or too slow (low-side recirculation)	5%⁽¹⁾
Dead-time is too short	4%⁽¹⁾
Incorrect SPI communication	12%
Incorrect input interpretation (nSLEEP)	1%
Incorrect nFAULT assertion	1%

(1) Divide this number by 12 for FMD of each individual OUTx pin.

DRV8912-Q1 was developed using a quality-managed development process, but was not developed in accordance with the IEC 61508 or ISO 26262 standards.

4 Pin Failure Mode Analysis (Pin FMA)

This section provides a failure mode analysis (FMA) for the pins of the DRV8912-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 VM (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 DRV8912-Q1 pin diagram. For a detailed description of the device pins, see the Pin Configuration and Functions section in the DRV8912-Q1 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:

The device is used with external components consistent with the values described in the external component table of the datasheet.

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
GND	1, 13, 24	Normal function.	D
OUT1	2	If OUT1 is commanded to be pulled high, short is detected and outputs are Hi-Z.	B
OUT5	3	If OUT5 is commanded to be pulled high, short is detected and outputs are Hi-Z.	B
OUT7	4	If OUT7 is commanded to be pulled high, short is detected and outputs are Hi-Z.	B
SDI	5	SPI communication is lost.	B
VDD	6	Device will be in SLEEP state and outputs are Hi-Z.	B
SDO	7	SPI communication is lost.	B
nSLEEP	8	Device will be in SLEEP state and outputs are Hi-Z.	B
OUT9	9	If OUT9 is commanded to be pulled high, short is detected and outputs are Hi-Z.	B
OUT6	10	If OUT6 is commanded to be pulled high, short is detected and outputs are Hi-Z.	B
OUT4	11	If OUT4 is commanded to be pulled high, short is detected and outputs are Hi-Z.	B
nFAULT	12	False fault signalling possible. Device will continue to operate as commanded.	B
OUT3	14	If OUT3 is commanded to be pulled high, short is detected and outputs are Hi-Z.	B
OUT10	15	If OUT10 is commanded to be pulled high, short is detected and outputs are Hi-Z.	B
VM	16, 21	Device is powered off with driver Hi-Z.	B
OUT11	17	If OUT11 is commanded to be pulled high, short is detected and outputs are Hi-Z.	B
OUT12	18	If OUT12 is commanded to be pulled high, short is detected and outputs are Hi-Z.	B
nSCS	19	SPI communication is lost.	B
SCLK	20	SPI communication is lost.	B
OUT8	22	If OUT8 is commanded to be pulled high, short is detected and outputs are Hi-Z.	B
OUT2	23	If OUT2 is commanded to be pulled high, short is detected and outputs are Hi-Z.	B

Table 4-3 Pin FMA for Device Pins Open-Circuited

Pin Name	Pin No.	Description of Potential Failure Effect(s)	Failure Effect Class
GND	1, 13, 24	Device is powered off with driver Hi-Z.	B
OUT1	2	Load drive capability is lost.	B
OUT5	3	Load drive capability is lost.	B
OUT7	4	Load drive capability is lost.	B
SDI	5	SPI communication is lost.	B
VDD	6	Device will be in SLEEP state and outputs are Hi-Z.	B
SDO	7	SPI communication is lost.	B
nSLEEP	8	Device will be in SLEEP state and outputs are Hi-Z.	B
OUT9	9	Load drive capability is lost.	B
OUT6	10	Load drive capability is lost.	B
OUT4	11	Load drive capability is lost.	B
nFAULT	12	False fault signaling possible. Device will continue to operate as commanded.	B
OUT3	14	Load drive capability is lost.	B
OUT10	15	Load drive capability is lost.	B
VM	16, 21	Device is powered off with driver Hi-Z.	B
OUT11	17	Load drive capability is lost.	B
OUT12	18	Load drive capability is lost.	B
nSCS	19	SPI communication is lost.	B
SCLK	20	SPI communication is lost.	B
OUT8	22	Load drive capability is lost.	B
OUT2	23	Load drive capability is lost.	B

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
GND	1	GND	Normal function.	D
OUT1	2	GND	If OUT1 is commanded to be pulled high, short is detected and OUT1 is Hi-Z.	B
OUT5	3	OUT1	Load drive capability is lost.	B
OUT7	4	OUT5	Load drive capability is lost.	B
SDI	5	OUT7	SPI communication is lost. Low voltage pin max voltage may be violated.	A
VDD	6	SDI	SPI communication is lost.	B
SDO	7	VDD	SPI communication is lost.	B
nSLEEP	8	SDO	SPI communication is lost.	B
OUT9	9	nSLEEP	Low voltage pin max voltage may be violated.	A
OUT6	10	OUT9	Load drive capability is lost.	B
OUT4	11	OUT6	Load drive capability is lost.	B
nFAULT	12	OUT4	False fault signalling possible. Low voltage pin max voltage may be violated.	A
GND	13	nFAULT	False fault signalling possible. Device will continue to operate as commanded.	B
OUT3	14	GND	If OUT3 is commanded to be pulled high, short is detected and OUT3 is Hi-Z.	B
OUT10	15	OUT3	Load drive capability is lost.	B
VM	16	OUT10	If OUT10 is commanded to be pulled low, short is detected and OUT10 is Hi-Z.	B
OUT11	17	VM	If OUT11 is commanded to be pulled low, short is detected and OUT11 is Hi-Z.	B
OUT12	18	OUT11	Load drive capability is lost.	B
nSCS	19	OUT12	SPI communication is lost. Low voltage pin max voltage may be violated.	A
SCLK	20	nSCS	SPI communication is lost.	B
VM	21	SCLK	SPI communication is lost. Low voltage pin max voltage may be violated.	A
OUT8	22	VM	If OUT8 is commanded to be pulled low, short is detected and OUT8 is Hi-Z.	B
OUT2	23	OUT8	Load drive capability is lost.	B
GND	24	OUT2	If OUT2 is commanded to be pulled high, short is detected and OUT2 is Hi-Z.	B

Table 4-5 Pin FMA for Device Pins Short-Circuited to VM

Pin Name	Pin No.	Description of Potential Failure Effect(s)	Failure Effect Class
GND	1, 13, 24	Device is powered off with driver Hi-Z.	B
OUT1	2	If OUT1 is commanded to be pulled low, short is detected and outputs are Hi-Z.	B
OUT5	3	If OUT5 is commanded to be pulled low, short is detected and outputs are Hi-Z.	B
OUT7	4	If OUT7 is commanded to be pulled low, short is detected and outputs are Hi-Z.	B
SDI	5	SPI communication is lost. Low voltage pin max voltage may be violated.	A
VDD	6	Low voltage pin max voltage may be violated.	A
SDO	7	SPI communication is lost. Low voltage pin max voltage may be violated.	A
nSLEEP	8	Low voltage pin max voltage may be violated.	A
OUT9	9	If OUT9 is commanded to be pulled low, short is detected and outputs are Hi-Z.	B
OUT6	10	If OUT6 is commanded to be pulled low, short is detected and outputs are Hi-Z.	B
OUT4	11	If OUT4 is commanded to be pulled low, short is detected and outputs are Hi-Z.	B
nFAULT	12	Low voltage pin max voltage may be violated.	A
OUT3	14	If OUT3 is commanded to be pulled low, short is detected and outputs are Hi-Z.	B
OUT10	15	If OUT10 is commanded to be pulled low, short is detected and outputs are Hi-Z.	B
VM	16, 21	Normal function.	D
OUT11	17	If OUT11 is commanded to be pulled low, short is detected and outputs are Hi-Z.	B
OUT12	18	If OUT12 is commanded to be pulled low, short is detected and outputs are Hi-Z.	B
nSCS	19	SPI communication is lost. Low voltage pin max voltage may be violated.	A
SCLK	20	SPI communication is lost. Low voltage pin max voltage may be violated.	A
OUT8	22	If OUT8 is commanded to be pulled low, short is detected and outputs are Hi-Z.	B
OUT2	23	If OUT2 is commanded to be pulled low, short is detected and outputs are Hi-Z.	B

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