SFFS950 October 2024 LM74930-Q1
4 Pin Failure Mode Analysis (Pin FMA)
This section provides a failure mode analysis (FMA) for the pins of the LM74930-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 LM74930-Q1 pin diagram. For a detailed description of the device pins please refer to the Pin Configuration and Functions section in the LM74930-Q1 data sheet.
Figure 4-1 Pin DiagramThe pin FMA is provided under the assumption that the device is operating under the specified ranges within the Recommended Operating Conditions section of the data sheet.
Table 4-2 Pin FMA for Device Pins Short-Circuited to Ground
| Pin Name | Pin No. | Description of Potential Failure Effects | Failure Effect Class |
|---|---|---|---|
| DGATE | 1 | Device is damaged due to internal conduction. External DGATE FET can also be damaged due to maximum VGS rating violation. | A |
| A | 2 | Input supply shorted to ground. Device is not functional. | B |
| SW | 3 | Device is damaged if enabled. | A |
| UVLO | 4 | Device HGATE drive is off. | B |
| OV | 5 | Overvoltage protection functionality is disabled. | B |
| EN | 6 | Device is in shutdown mode. | B |
| MODE | 7 | Device disables reverse-current blocking feature. | B |
| NC | 8, 17, 21 | No effect on device operation. | D |
| TMR | 9 | Timer functionality is not available. | B |
| IMON | 10 | Current monitoring output is not available. | B |
| ILIM | 11 | Overcurrent protection, with circuit breaker feature, is not be available. | B |
| FLT | 12 | Fault indication functionality is not be available. | B |
| GND | 13 | No impact on the device functionality. | D |
| HGATE | 14 | Device is damaged. | A |
| OUT | 15 | External FET VGS(max) rating can be exceeded and damage the external FET. Device can experience an increase in quiescent current. | D |
| OVCLAMP | 16 | Overvoltage clamp, with circuit breaker timer functionality, is disabled. | B |
| ISCP | 18 | Device damage is expected due to internal current flow. | A |
| CS- | 19 | Device damage is expected due to internal current flow. | A |
| CS+ | 20 | Device damage is expected due to internal current flow. | A |
| VS | 22 | Device does not power up. | B |
| CAP | 23 | Device is damaged due to internal conduction between VS and CAP. | A |
| C | 24 | Linear regulation and reverse current blocking functionality is not available. Device quiescent current can increase. | B |
| RTN | — | Input reverse-polarity protection feature is not available. | B |
Table 4-3 Pin FMA for Device Pins Open Circuited
| Pin Name | Pin No. | Description of Potential Failure Effects | Failure Effect Class |
|---|---|---|---|
| DGATE | 1 | Preferred diode FET can not be controlled. Reverse-current blocking feature is not available. Load current flows through body diode of the FET. | B |
| A | 2 | Preferred diode FET is turned off due to linear regulation sink current. Load current flows through body diode of the FET. | B |
| SW | 3 | Battery voltage monitoring feature is not available. | B |
| UVLO | 4 | Device HGATE drive is off due to internal pull down on UVLO pin. | B |
| OV | 5 | Overvoltage protection functionality is disabled as OV pin is internally pulled low. | B |
| EN | 6 | Device is in shutdown mode as EN pin is internally pulled low. | B |
| MODE | 7 | Device enables reverse-current blocking feature. | B |
| NC | 8, 17, 21 | No effect on device operation. | D |
| TMR | 9 | Device operation with default timer operation. Auto retry timer can not be set using external timer capacitor. | B |
| IMON | 10 | Current monitoring output is not available. | B |
| ILIM | 11 | ILIM pin is pulled high and device is in overcurrent protection mode. | B |
| FLT | 12 | Fault indication functionality is not available. | B |
| GND | 13 | Device does not power up. | D |
| HGATE | 14 | HGATE control to turn on or turn off the external FET is not available. | B |
| OUT | 15 | HGATE control to turn on or turn off the external FET is not available. | D |
| OVCLAMP | 16 | Overvoltage clamp with circuit breaker timer functionality disabled. | B |
| ISCP | 18 | Short circuit protection feature is not available. | B |
| CS- | 19 | Device is in overcurrent protection mode and HGATE drive is turned off. | B |
| CS+ | 20 | Overcurrent protection and current monitoring output is not available. | B |
| VS | 22 | Device does not power up. | B |
| CAP | 23 | Charge pump does not build up and gate drives DGATE and HGATE are disabled. | B |
| C | 24 | DGATE drive remains off. | B |
| RTN | — | No effect on device operation. | D |
Table 4-4 Pin FMA for Device Pins Short Circuited to Adjacent Pin
| Pin Name | Pin No. | Description of Potential Failure Effects | Failure Effect Class |
|---|---|---|---|
| DGATE | 1 | Preferred diode FET is off. Load current flows through body diode of the FET. | B |
| A | 2 | No effect on device operation. | D |
| SW | 3 | UVLO feature is not available. | B |
| UVLO | 4 | Either OV or UVLO comparator trigger and HGATE is off. | B |
| OV | 5 | HGATE drive is off in case device is enabled (EN = High). | B |
| EN | 6 | No effect on device operation. | D |
| MODE | 7 | Reverse-current blocking feature is enabled if adjacent pin voltage is high and feature is disabled if adjacent pin voltage is low. | D |
| NC | 8, 17, 21 | No effect on device operation. | D |
| TMR | 9 | Timer (TMR) and current monitoring (IMON) functionality are out of data sheet specification. | B |
| IMON | 10 | Current monitoring output is out of data sheet specification. | B |
| ILIM | 11 | Device is in overcurrent protection mode based on FLT voltage level. | B |
| FLT | 12 | No effect on device operation. | D |
| GND | 13 | GND shorted to HGATE can cause device damage. | A |
| HGATE | 14 | HGATE FET is off as HGATE is shorted to OUT causing VGS short condition. | B |
| OUT | 15 | No effect on device operation. Device supports only overvoltage clamp operation during SLEEP mode. | B |
| OVCLAMP | 16 | OVCLAMP shorted to OUT results in TIMER start when OUT pin voltage rises above V(OVCLAMPR) and HGATE turns off when TIMER expires. | B |
| ISCP | 18 | No effect on device operation. | D |
| CS- | 19 | Short circuit and overcurrent protection is not available. | B |
| CS+ | 20 | Overcurrent limit, current monitoring output parameters are out of specification. | B |
| VS | 22 | Device charge pump does not come up. DGATE and HGATE drive are off. | B |
| CAP | 23 | Device charge pump does not come up. DGATE and HGATE drive are off. | B |
| C | 24 | No effect on device operation. | B |
| RTN | — | No effect on device operation. | D |
Table 4-5 Pin FMA for Device Pins Short Circuited to Supply
| Pin Name | Pin No. | Description of Potential Failure Effects | Failure Effect Class |
|---|---|---|---|
| DGATE | 1 | DGATE is shorted to supply. Preferred diode FET remains off. | B |
| A | 2 | No effect on device operation. | D |
| SW | 3 | Battery voltage monitoring feature is available, irrespective of EN pin status. | B |
| UVLO | 4 | UVLO functionality is not available. | B |
| OV | 5 | HGATE is turned off due to OV comparator input going high. | B |
| EN | 6 | Device is always on as EN is pulled to supply. | B |
| MODE | 7 | Reverse-current blocking feature is enabled. | B |
| NC | 8, 17, 21 | No effect on device operation. | D |
| TMR | 9 | Device is damaged if supply voltage level is >5.5V. | A |
| IMON | 10 | Device is damaged if supply voltage level is >5.5V. | A |
| ILIM | 11 | Device is damaged if supply voltage level is >5.5V. | A |
| FLT | 12 | Fault indication functionality is not available. | B |
| GND | 13 | Device does not power up due to supply shorted to GND. | D |
| HGATE | 14 | HGATE control to turn on or turn off the external FET is not available. Device quiescent current can increase. | B |
| OUT | 15 | Supply is shorted to output. Preferred diode (DGATE), load disconnect (HGATE) features are not functional as supply is shorted to output. | B |
| OVCLAMP | 16 | Timer starts as supply rises above V(OVCLAMPR) and HGATE turns OFF after timer expires. | B |
| ISCP | 18 | Device has default short circuit protection threshold of 20mV. | B |
| CS- | 19 | Overcurrent protection functionality is not available. | B |
| CS+ | 20 | Device is in overcurrent protection mode. | B |
| VS | 22 | No effect on device operation. | B |
| CAP | 23 | Charge pump does not build up and gate drives DGATE and HGATE are disabled. | B |
| C | 24 | Preferred diode functionality is not available (reverse-current blocking). | B |
| RTN | — | No effect on device operation. | D |