SLVAEL8A December 2019 – October 2022 TPS7B68-Q1
This section provides a failure mode analysis (FMA) for the pins of the TPS7B68-Q1. 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 TPS7B68-Q1 pin diagram. For a detailed description of the device pins, see the Pin Configuration and Functions section in the TPS7B68-Q1 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 Effects | Failure Effect Class |
|---|---|---|---|
| IN | 1 | No power is supplied to the device, resulting in no output voltage. | B |
| NC | 2 | No effect. Normal operation. | D |
| NC | 3 | No effect. Normal operation. | D |
| EN | 4 | The device is disabled, resulting in no output voltage. | B |
| FSEL | 5 | The device operates with the high-frequency oscillator selected. | B |
| WTS | 6 | The device operates with the window watchdog-timer. | B |
| NC | 7 | No effect. Normal operation. | D |
| GND | 8 | No effect. Normal operation. | D |
| NC | 9 | No effect. Normal operation. | D |
| NC | 10 | No effect. Normal operation. | D |
| ROSC | 11 | A fault is reported at WDO. | B |
| DELAY | 12 | The power-good delay becomes infinite. PG is unable to assert high. | B |
| WD | 13 | Watchdog functionality is never serviced, resulting in error reported at WDO. | B |
| NC | 14 | No effect. Normal operation. | D |
| WDO | 15 | Watchdog cannot assert high. | B |
| WD_EN | 16 | Watchdog functionality is always enabled. | B |
| NC | 17 | No effect. Normal operation. | D |
| WRS | 18 | Sets the open:closed window ratio to 1:1. | B |
| NC | 19 | No effect. Normal operation. | D |
| NC | 20 | No effect. Normal operation. | D |
| GND | 21 | No effect. Normal operation. | D |
| NC | 22 | No effect. Normal operation. | D |
| NC | 23 | No effect. Normal operation. | D |
| PG | 24 | PG is unable to assert high. | B |
| PGADJ | 25 | Sets the PG threshold to 91.6% of VOUT. | B |
| NC | 26 | No effect. Normal operation. | D |
| NC | 27 | No effect. Normal operation. | D |
| OUT | 28 | Regulation is not possible, the device operates at current limit and can cycle in and out of thermal shutdown. | B |
| Pin Name | Pin No. | Description of Potential Failure Effects | Failure Effect Class |
|---|---|---|---|
| IN | 1 | No power is supplied to the device, resulting in no output voltage. | B |
| NC | 2 | No effect. Normal operation. | D |
| NC | 3 | No effect. Normal operation. | D |
| EN | 4 | The enable circuit is in an unknown state. The device is either enabled or disabled. | B |
| FSEL | 5 | The frequency-select circuitry is in an unknown state. The watchdog timer window is either high-frequency or low-frequency. | B |
| WTS | 6 | The watchdog type selection circuitry is in an unknown state. The watchdog is either in windowed mode or standard operation. | B |
| NC | 7 | No effect. Normal operation. | D |
| GND | 8 | There is no current loop for the supply
voltage. The device is not operational and does not regulate. There is also a possibility that the absolute maximum value of the device pins are exceeded, causing internal damage to the transistors. |
A |
| NC | 9 | No effect. Normal operation. | D |
| NC | 10 | No effect. Normal operation. | D |
| ROSC | 11 | A fault is reported at WDO. | B |
| DELAY | 12 | The power-good circuitry responds with no delay. | B |
| WD | 13 | The watchdog timer does not receive the service-signal and reports an error at WDO. | B |
| NC | 14 | No effect. Normal operation. | D |
| WDO | 15 | The watchdog output signal is unconnected and unreadable. The watchdog output on the device is not representative of the watchdog fault control behavior. | B |
| WD_EN | 16 | The watchdog enable circuitry is in an unknown state. The watchdog is either enabled or disabled. | B |
| NC | 17 | No effect. Normal operation. | D |
| WRS | 18 | (Standard watchdog operation.) No
effect. Normal operation. (Window watchdog operation.) The watchdog ratio select circuitry is in an unknown state. The watchdog ratio is either 1:1 or 8:1. |
D/B |
| NC | 19 | No effect. Normal operation. | D |
| NC | 20 | No effect. Normal operation. | D |
| GND | 21 | There is no current loop for the supply
voltage. The device is not operational and does not regulate. There is also a possibility that the absolute maximum value of the device pins are exceeded, causing internal damage to the transistors. |
A |
| NC | 22 | No effect. Normal operation. | D |
| NC | 23 | No effect. Normal operation. | D |
| PG | 24 | The PG signal is unconnected and unreadable. The PG flag state on the device is not representative of VOUT. | B |
| PGADJ | 25 | The PGADJ circuitry is in an unknown state. The PG trip threshold is unknown and the PG output becomes unreliable. | B |
| NC | 26 | No effect. Normal operation. | D |
| NC | 27 | No effect. Normal operation. | D |
| OUT | 28 | The device output is disconnected from the load. | B |
| Pin Name | Pin No. | Shorted to | Description of Potential Failure Effects | Failure Effect Class |
|---|---|---|---|---|
| IN | 1 | NC (pin 2) | No effect. Normal operation. | D |
| NC | 2 | NC (pin 3) | No effect. Normal operation. | D |
| NC | 3 | EN (pin 4) | No effect. Normal operation. | D |
| EN | 4 | FSEL (pin 5) | The device can be enabled or disabled
depending on the FSEL pin voltage. The low-frequency or high-frequency oscillator option can be selected depending on the EN pin voltage. |
B |
| FSEL | 5 | WTS (pin 6) | The low-frequency or high-frequency
oscillator option can be selected depending on the WTS pin
voltage. The standard or window watchdog timer can be selected depending on the FSEL pin voltage. |
B |
| WTS | 6 | NC(pin 7) | No effect. Normal operation. | D |
| NC | 7 | GND (pin 8) | No effect. Normal operation. | D |
| GND | 8 | NC (pin 9) | No effect. Normal operation. | D |
| NC | 9 | NC (pin 10) | No effect. Normal operation. | D |
| NC | 10 | ROSC (pin 11) | No effect. Normal operation. | D |
| ROSC | 11 | DELAY (pin 12) | A fault can be reported at WDO depending
on the DELAY pin voltage. PG has no delay. |
B |
| DELAY | 12 | WD (pin 13) | The PG delay time is affected depending
on the WD pin voltage. The watchdog timer does not receive a service-signal properly, causing a fault to be output at WDO. |
B |
| WD | 13 | NC (pin 14) | No effect. Normal operation. | D |
| WDO | 15 | WD_EN (pin 16) | The WDO flag state is always low if
enabled, and is DNC when disabled. The watchdog can be disabled or enabled depending on the voltage level of the WDO pin. |
B |
| WD_EN | 16 | NC (pin 17) | No effect. Normal operation. | D |
| NC | 17 | WRS (pin 18) | No effect. Normal operation. | D |
| WRS | 18 | NC (pin19) | No effect. Normal operation. | D |
| NC | 19 | NC (pin 20) | No effect. Normal operation. | D |
| NC | 20 | GND (pin 21) | No effect. Normal operation. | D |
| GND | 21 | NC (pin 22) | No effect. Normal operation. | D |
| NC | 22 | NC (pin 23) | No effect. Normal operation. | D |
| NC | 23 | PG (pin 24) | No effect. Normal operation. | D |
| PG | 24 | PGADJ (pin 25) | The PG flag state can be incorrect,
depending on the PGADJ pin voltage. The PGADJ threshold can be affected. |
B |
| PGADJ | 25 | NC (pin 26) | No effect. Normal operation. | D |
| NC | 26 | NC (pin 27) | No effect. Normal operation. | D |
| NC | 27 | OUT (pin 28) | No effect. Normal operation. | D |
| Pin Name | Pin No. | Description of Potential Failure Effects | Failure Effect Class |
|---|---|---|---|
| IN | 1 | No effect. Normal operation. | D |
| NC | 2 | No effect. Normal operation. | D |
| NC | 3 | No effect. Normal operation. | D |
| EN | 4 | The device is always on when VIN is supplied. | B |
| FSEL | 5 | The device operates with the low-frequency oscillator when VIN is supplied. | B |
| WTS | 6 | The device operates with the standard watchdog timer when VIN is supplied. | B |
| NC | 7 | No effect. Normal operation. | D |
| GND | 8 | No output voltage. System performance depends on upstream current limiting. | B |
| NC | 9 | No effect. Normal operation. | D |
| NC | 10 | No effect. Normal operation. | D |
| ROSC | 11 | The watchdog timer does not operate
properly. ROSC becomes damaged if VIN exceeds the ROSC maximum voltage. |
A |
| DELAY | 12 | PG does not have a delay. PG becomes damaged if VIN exceeds the PG maximum voltage. |
A |
| WD | 13 | The watchdog timer does not receive the
service signal and reports and error at WDO. WD becomes damaged if VIN exceeds the WD maximum voltage. |
A |
| NC | 14 | No effect. Normal operation. | D |
| WDO | 15 | WDO is unable to assert low. WDO becomes damaged if VIN exceeds the WDO maximum voltage. |
A |
| WD_EN | 16 | The watchdog timer is always disabled. WD_EN becomes damaged if VIN exceeds the WD_EN maximum voltage. |
A |
| NC | 17 | No effect. Normal operation. | D |
| WRS | 18 | Sets the watchdog window ratio to 1:1. WRS becomes damaged if VIN exceeds the WRS maximum voltage. |
A |
| NC | 19 | No effect. Normal operation. | D |
| NC | 20 | No effect. Normal operation. | D |
| GND | 21 | No output voltage. System performance depends on upstream current limiting. | B |
| NC | 22 | No effect. Normal operation. | D |
| NC | 23 | No effect. Normal operation. | D |
| PG | 24 | PG is unable to assert low. PG becomes damaged if VIN exceeds the PG maximum voltage. |
A |
| PGADJ | 25 | PGADJ becomes damaged if VIN exceeds the PGADJ maximum voltage. | A |
| NC | 26 | No effect. Normal operation. | D |
| NC | 27 | No effect. Normal operation. | D |
| OUT | 28 | No VOUT regulation. Output voltage is
the same as the input voltage. OUT becomes damaged if VIN exceeds the OUT maximum voltage. |
A |