SFFS052 January 2021 TPS2HB35-Q1
4 Pin Failure Mode Analysis (Pin FMA)
This section provides a Failure Mode Analysis (FMA) for the pins of the TPS2HB35-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.
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 TPS2HB35-Q1 pin diagram. For a detailed description of the device pins please refer to the Pin Configuration and Functions section in the TPS2HB35-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:
- Follows data sheet recommendation for operating conditions, external component selection and PCB layout
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 | 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 |
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 | The output is off with the FET turned off. | B |
| SNS | 2 | SNS current diagnostic not 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 |
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 | 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 |
Table 4-5 Pin FMA for Device Pins
Short-Circuited to
supply
| 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 |