TPS2HB50-Q1Functional Safety FIT Rate, FMD and Pin FMA
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1 Overview
This document contains information for TPS2HB50-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 DiagramTPS2HB50-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 TPS2HB50-Q1 based on industry-wide used reliability standard:
- Table 2-1 provides FIT rates based on IEC TR 62380 / ISO 26262 part 11
| FIT IEC TR 62380 / ISO 26262 | FIT (Failures Per 109 Hours) |
|---|---|
| Total Component FIT Rate | 22 |
| Die FIT Rate | 12 |
| Package FIT Rate | 10 |
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: 750 mW
- Climate type: World-wide Table 8 IEC TR 62380
- Package factor (lambda 3): Table 17b IEC TR 62380
- Substrate Material: FR4
- EOS FIT rate assumed: 0 FIT
3 Failure Mode Distribution (FMD)
The failure mode distribution estimation for TPS2HB50-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 (%) |
|---|---|
| VOUT open (HiZ) | 20% |
| VOUT stuck on (VBB) | 10% |
| VOUT functional, not in specification voltage or timing | 45% |
| Diagnostics not in specification | 10% |
| Protect functions fails to trip | 10% |
| Pin to Pin short any two pins | 5% |
4 Pin Failure Mode Analysis (Pin FMA)
This section provides a Failure Mode Analysis (FMA) for the pins of the TPS2HB50-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 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.
| 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 TPS2HB50-Q1 pin diagram. For a detailed description of the device pins please refer to the Pin Configuration and Functions section in the TPS2HB50-Q1 data sheet.
Figure 4-1 Pin DiagramFollowing are the assumptions of use and the device configuration assumed for the pin FMA in this section:
- Follow data sheet recommendation for operating conditions, external component selection and PCB layout
| Pin Name | Pin No. | Description of Potential Failure Effect(s) | Failure Effect Class |
|---|---|---|---|
| GND | 1 | Resistor/diode network will be bypassed if present | B |
| SNS | 2 | SNS current diagnostic not available. | B |
| LATCH | 3 | Normal operation. With device in auto-retry mode. | B |
| EN1 | 4 | Normal operation with channel 1 output off (FET turned off). | B |
| ILIM1 | 5 | Current Limit for channel 1 defaults to internal limit. | C |
| VOUT1 | 6,7,8 | Short to GND protection kicks in to protect the device. | B |
| VOUT2 | 9,10,11 | Short to GND protection kicks in to protect the device. | B |
| ILIM2 | 12 | Current Limit for channel 2 defaults to internal limit. | C |
| EN2 | 13 | Normal operation with channel 2 output off (FET turned off). | B |
| SEL1 | 14 | Normal operation with diagnostics corresponding to SEL1=LOW. | B |
| SEL2 | 15 | Normal operation with diagnostics corresponding to SEL2=LOW. | B |
| DIAG_EN | 16 | Normal operation with diagnostics function disabled. | B |
| Pin Name | Pin No. | Description of Potential Failure Effect(s) | Failure Effect Class |
|---|---|---|---|
| GND | 1 | The output is off with the FET turned off. | B |
| SNS | 2 | SNS current diagnostic no available. | B |
| LATCH | 3 | Normal operation with device in auto-retry mode. Internal pull=down resistor will pull pin to GND. | B |
| EN1 | 4 | Normal operation with channel 1 output off (FET turned off). Internal pull-down resistor will pull pin to GND. | B |
| ILIM1 | 5 | Current Limit for channel 1 defaults to internal limit. | C |
| VOUT1 | 6,7,8 | Channel 1 Output off. Open load detection will be triggered in off-state while in diagnostics state. | B |
| VOUT2 | 9,10,11 | Channel 2 Output off. Open load detection will be triggered in off-state while in diagnostics state. | B |
| ILIM2 | 12 | Current Limit for channel 2 defaults to internal limit. | C |
| EN2 | 13 | Normal operation with channel 2 output off (FET turned off). Internal pull-down resistor will pull pin to GND. | B |
| SEL1 | 14 | Normal operation with diagnostics corresponding to SEL1=LOW. Internal pull-down resistor will pull pin to GND. | B |
| SEL2 | 15 | Normal operation with diagnostics corresponding to SEL2=LOW. Internal pull-down resistor will pull pin to GND. | B |
| DIAG_EN | 16 | Normal operation with diagnostics function disabled. Internal pull-down resistor will pull pin to GND. | B |
| Pin Name | Pin No. | Shorted to | Description of Potential Failure Effect(s) | Failure Effect Class |
|---|---|---|---|---|
| GND | 1 | 2 (SNS) | SNS current diagnostic not available. | B |
| SNS | 2 | 3 (LATCH) | Undefined device behavior and depends on pin voltage. Sense output may not be correct. Latch function may be enabled if pin voltage > VIH; latch function may be disabled if pin voltage < VIL. | B |
| LATCH | 3 | 4 (EN) | Device behavior depends on pin voltage. Latch function may be enabled if pin voltage > VIH; Latch function may be disabled if pin voltage < VIL. | B |
| EN1 | 4 | 5 (ILIM1) | Undefined device behavior. Channel may be enabled if pin voltage > VIH; channel may be disabled if pin voltage < VIL. Channel 1 current limit threshold will not be correct. | B |
| ILIM1 | 5 | 6 (VOUT) | Undefined device behavior. Current limit threshold (ch1) will not be correct or short circuit/overload protection may not function. VOUT of Ch1 behavior may not be correct. | A |
| VOUT1 | 6,7,8 | 5 (ILIM1) | Undefined device behavior. Current limit threshold (ch1) will not be correct or short circuit/overload protection may not function. VOUT of Ch1 behavior may not be correct. | A |
| VOUT2 | 9,10,11 |
12 (ILIM2) |
Undefined device behavior. Current limit threshold (ch2) will not be correct or short circuit/overload protection may not function. VOUT of Ch2 behavior may not be correct. |
A |
| ILIM2 | 12 | 13 (EN2) | Undefined device behavior. Channel 2 may be enabled if pin voltage > VIH; channel 2 may be disabled if pin voltage < VIL. Channel 2 current limit threshold will not be correct. | B |
| EN2 | 13 |
14 (SEL1) |
Undefined device behavior. Ch2 may be enabled if pin voltage > VIH; Ch2 may be disabled if pin voltage < VIL. |
B |
| SEL1 | 14 | 15 (SEL2) | Device behavior depends on adjacent pin voltage affecting diagnostic output. | B |
| SEL2 | 15 | 16 (DIAG_EN) | Device behavior depends on adjacent pin voltage affecting diagnostic output. Diagnostic function may be enabled if pin voltage > VIH; Diagnostic function may be disabled if pin voltage < VIL. | B |
| DIAG_EN | 16 | 15 (SEL2) | Device behavior depends on adjacent pin voltage affecting diagnostic output. Diagnostic function may be enabled if pin voltage > VIH; Diagnostic function may be disabled if pin voltage < VIL. | B |
| Pin Name | Pin No. | Description of Potential Failure Effect(s) | Failure Effect Class |
|---|---|---|---|
| GND | 1 | Supply power will be bypassed and device will not turn on | B |
| SNS | 2 | Undefined device behavior; may cause device damage due to voltage breakdown on ESD circuit | A |
| LATCH | 3 | If pin voltage exceeds the pin data sheet range, it may cause device damage due to voltage breakdown on ESD circuit. Device behavior depends on supply voltage. | A |
| EN1 | 4 | Undefined device behavior; if pin voltage exceeds the pin data sheet range, it may cause device damage due to voltage breakdown on ESD circuit. | A |
| ILIM1 | 5 | Normal operation but with ch1 higher current limit programmed with internal reference. | C |
| VOUT | 6,7,8,9,10,11 | Output 1 stuck on to supply. Open load detection will be triggered in off-state in diagnostics state. | C |
|
VOUT2 |
9,10,11 |
Output 2 stuck on to supply. Open load detection will be triggered in off-state in diagnostics state. |
C |
| ILIM2 | 12 | Normal operation but with ch2 higher current limit programmed with internal reference. | C |
|
EN2 |
13 |
Undefined device behavior; if pin voltage exceeds the pin data sheet range, it may cause device damage due to voltage breakdown on ESD circuit. |
A |
| SEL1 | 14 | Undefined device behavior; if pin voltage exceeds the pin data sheet range, it may cause device damage due to voltage breakdown on ESD circuit. | A |
|
SEL2 |
15 |
Undefined device behavior; if pin voltage exceeds the pin data sheet range, it may cause device damage due to voltage breakdown on ESD circuit. |
A |
| DIAG_EN | 16 | Undefined device behavior; if pin voltage exceeds the pin data sheet range, it may cause device damage due to voltage breakdown on ESD circuit. | A |
