SFFS607 april   2023 TPS3435 , TPS3435-Q1 , TPS3436-Q1 , TPS35 , TPS35-Q1 , TPS36-Q1

 

  1.   1
  2.   Trademarks
  3. 1Overview
  4. 2Functional Safety Failure In Time (FIT) Rates
  5. 3Failure Mode Distribution (FMD)
  6. 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 TPS3435, TPS3436, TPS35, and TPS36. 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 supply (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
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 and Figure 4-2 shows the TPS3435, TPS3436, TPS35, and TPS36 pin diagrams. For a detailed description of the device pins please refer to TPS3435, TPS3436, TPS35, or TPS36 in the Pin Configuration and Functions section of the data sheet.

GUID-20210630-CA0I-08RM-BC36-BJPP13DHFRN7-low.svgFigure 4-1 Pin Configuration Option B
DDF Package,8-Pin SOT-23,
TPS35 and TPS36 Top View
GUID-20210630-CA0I-JJVM-RDRQ-CS9QJCDH2PV8-low.svgFigure 4-2 Pin Configuration Option B
DDF Package,8-Pin SOT-23,
TPS3435 and TPS3436 Top View

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

  • Output reset Pullup Resistor (RPULLUP) = 10 kΩ, Output reset pullup voltage (VPULLUP = 5.5 V, output reset load (CLOAD) = 10 pF.
  • Tables valid over the operating free-air temperature range of – 40°C to 125°C, unless otherwise noted.
  • Typical values are at TA = 25°C, VDD = 6.0 V unless stated otherwise.
Table 4-2 Pin FMA for Device Pins Short-Circuited to Ground
PIN NAMEPIN NO.DESCRIPTION OF POTENTIAL FAILURE EFFECT(S)FAILURE EFFECT CLASS
SET01

Unexpected behavior if application needs SET0 = 1.

B

CWD

2

Capacitance value is detected after startup, or error detection. If it's shorted to ground then the WD is disabled.

B

CRST (TPS35 and TPS36)

3

tD is the max value. Please refer to the switching characteristics table in the TPS35, or TPS36 data sheets for more information.

B

CRST (TPS3435 and TPS3436)

3

WDO stays asserted.

B

GND

4

Expected operating condition.

D

SET15

Unexpected behavior if application needs SET1 = 1.

B

WDI

6Constant WD timeout faults.B
WDO / RESET(Open Drain)7

WDO / RESET constantly asserted; some additional current can flow through pullup resistor.

B

WDO / RESET(Push Pull)7Functionality lost and can cause permanent damage.

A

VDD8Device non-operational.

B

Table 4-3 Pin FMA for Device Pins Open-Circuited
PIN NAMEPIN NO.DESCRIPTION OF POTENTIAL FAILURE EFFECT(S)FAILURE EFFECT CLASS
SET01

Leads to large indeterminate voltage levels. This causes large currents that can damage the device. The output behavior is not deterministic.

A
CWD2

Output is asserted.

B
CRST3Nothing happens until error condition, then reset delay is 2 mS.C
GND4Device is non-operational.B
SET15Leads to large indeterminate voltage levels. This causes large currents that can damage the device. The output behavior is not deterministic.A
WDI6Leads to large indeterminate voltage levels. This causes large currents that can damage the device.A
WDO / RESET(Open Drain)7Constant high, no WDO/RESET functionality.B
WDO / RESET(Push Pull)7High impedance output, no WDO/RESET functionality.B
VDD8Device is non-operational.

B

Table 4-4 Pin FMA for Device Pins Short-Circuited to Adjacent Pin
PIN NAMEPIN NO.SHORTED TODESCRIPTION OF POTENTIAL FAILURE EFFECT(S)FAILURE EFFECT CLASS
SET01

CWD

If SET0 is pulled up with a resistor, then the device can charge CWD capacitor at an unpredictable rate that depends on pullup resistor value. If SET0 is low, then the WD is disabled.

C

CWD

2

CRST

Device stays in error condition. Output assert time can be higher than expected. If either capacitor is outside the range, then the WD can be disabled.

B

CRST (TPS35 and TPS36)3

GND

tD is the max value. Please refer to the switching characteristics table in the TPS35, or TPS36 data sheets for more information.

B

CRST (TPS3435 and TPS3436)

3

GND

WDO stays asserted.

B

GND4SET1

Unexpected behavior if application needs SET1 = 1.

B

SET15

WDI

SET1 toggles with WDI.

B

WDI

6WDO / RESET(Open Drain)Incorrect error ouput. If WDI is being driven high, then high current can flow into an active low WDO/RESET. This causes damage if the current is higher than the abs max. Please refer to the Absolute Maximum Ratings table in the TPS3435, TPS3436, TPS35, or TPS36 data sheets for more information.

A

WDI

6WDO / RESET(Push Pull)Incorrect error ouput. If WDI is being driven high, then high current can flow into an active low WDO/RESET. This causes damage if the current is higher than the abs max. Please refer to the Absolute Maximum Ratings table in the TPS3435, TPS3436, TPS35, or TPS36 data sheets for more information.

A

WDO / RESET(Open Drain)7VDD

Large current can flow into WDO/RESET when in error condition. This can cause permanant damage.

A

WDO / RESET(Push Pull)7VDD

Can cause permanent damage.

A

VDD

8SET0

Unexpected behavior if application needs SET0 = 0.

B

Table 4-5 Pin FMA for Device Pins Short-Circuited to VDD
PIN NAMEPIN NO.DESCRIPTION OF POTENTIAL FAILURE EFFECT(S)FAILURE EFFECT CLASS
SET01Unexpected behavior if application needs SET0 = 0.

B

CWD2WDO / RESET asserts. Possibility of high current which can cause device damage.A
CRST3

tD is 2 ms. Possibility of high current which can cause device damage.

A

GND4

Device is non-operational.

B

SET15Unexpected behavior if application needs SET1 = 0.

B

WDI6

Constant WD timeout faults.

B
WDO / RESET(Open Drain)7Large current can flow into WDO/RESET when in error condition. This can cause permanant damage.A
WDO / RESET(Push Pull)7Can cause permanent damage.

A

VDD8Normal operation.

D