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This document contains information for TPS3702 (DDC package) to aid in a functional safety system design. Information provided are:
Figure 1-1 shows the device functional block diagram for reference.
TPS3702 was developed using a quality-managed development process, but was not developed in accordance with the IEC 61508 or ISO 26262 standards.
This section provides Functional Safety Failure In Time (FIT) rates for TPS3702 based on two different industry-wide used reliability standards:
FIT IEC TR 62380 / ISO 26262 | FIT (Failures Per 109 Hours) |
---|---|
Total Component FIT Rate | 4 |
Die FIT Rate | 2 |
Package FIT Rate | 2 |
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 | CMOS,
BICMOS 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 TPS3702 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 (%) |
---|---|
UV or OV output HiZ | 30% |
UV or OV output stuck low | 30% |
UV or OV output operating outside of specification | 40% |
This section provides a Failure Mode Analysis (FMA) for the pins of the TPS3702. The failure modes covered in this document include the typical pin-by-pin failure scenarios:
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 TPS3702 pin diagram. For a detailed description of the device pins please refer to the Pin Configuration and Functions section in the TPS3702 data sheet.
Following are the assumptions of use and the device configuration assumed for the pin FMA in this section:
Pin Name | Pin No. | Description of Potential Failure Effect(s) | Failure Effect Class |
---|---|---|---|
UV | 1 | No damage to device, undervoltage output pin nonfunctional, increase in system current. | B |
GND | 2 | No effect. | D |
SENSE | 3 | No damage to device, Undervoltage output always active, Overvoltage output always inactive. | B |
OV | 4 | No damage to device, Overvoltage output pin nonfunctional, increase in system current. | B |
VDD | 5 | No damage to device, but device is unpowered. Device is nonfunctional. | B |
SET | 6 | No damage to device, wide thresholds selected. | B |
Pin Name | Pin No. | Description of Potential Failure Effect(s) | Failure Effect Class |
---|---|---|---|
UV | 1 | No damage to device, undervoltage output pin nonfunctional. | B |
GND | 2 | No damage to device, but device is unpowered. Device is nonfunctional. | B |
SENSE | 3 | No damage to device. Due to internal resistor ladder for setting trip points open SENSE pin behaves as though GND potential - Undervoltage output always active, Overvoltage output always inactive. | B |
OV | 4 | No damage to device, overvoltage output pin nonfunctional. | B |
VDD | 5 | No damage to device, but device is unpowered. Device is nonfunctional. | B |
SET | 6 | No damage to device. Due to internal pull up on SET pin it behaves as if connected to VDD - narrow thresholds selected. | B |
Pin Name | Pin No. | Shorted to | Description of Potential Failure Effect(s) | Failure Effect Class |
---|---|---|---|---|
UV | 1 | GND | No damage to device, undervoltage output pin nonfunctional, increase in system current. | B |
GND | 2 | SENSE | No damage to device, Undervoltage output always active, Overvoltage output always inactive. | B |
SENSE | 3 | SET | Since SET VIH = 750mV and all SENSE thresholds >1V, SENSE = SET means always narrow threshold tolerances selected. | B |
OV | 4 | UV | No damage to device, but device is nonfunctional with both outputs tied together, can’t distinguish OV from UV. | B |
VDD | 5 | OV | No damage to device, overvoltage output pin nonfunctional. | B |
SET | 6 | VDD | No damage to device, narrow thresholds selected. | B |
Pin Name | Pin No. | Description of Potential Failure Effect(s) | Failure Effect Class |
---|---|---|---|
UV | 1 | No damage to device, undervoltage output pin nonfunctional. | B |
GND | 2 | No damage to device, but device is unpowered. Device is nonfunctional. | B |
SENSE | 3 | No damage to device, Undervoltage output always inactive, Overvoltage output always active. | B |
OV | 4 | No damage to device, overvoltage output pin nonfunctional. | B |
VDD | 5 | No effect. | D |
SET | 6 | No damage to device, narrow thresholds selected. | B |
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