SFFS052 January   2021 TPS2HB35-Q1

 

  1.   Trademarks
  2. 1Overview
  3. 2Functional Safety Failure In Time (FIT) Rates
  4. 3Failure Mode Distribution (FMD)
  5. 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 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
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 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.

GUID-714552FE-3FA6-4E96-8AE7-300DC1576418-low.gif Figure 4-1 Pin Diagram

Following 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