The following faults are registered on the FLTx pin:

• FET thermal shutdown
• Active current regulation
• Thermal Shutdown caused by current limitation
• Open-load (FET OFF state only)

Open-load or short-to-supply are not indicated while the switch is enabled, although in on-state these conditions can still be detected through the sensed current (ISNS current). Hence, if there is a fault indication while the channel is enabled, then it must be either due to an overcurrent or overtemperature event. On the other hand, a fault indication while the output (FET) is disabled must be either due to an open load or output short-to-supply.

In versions A, B, C of the device, the open drain FLT pin output is a global fault output. FLT pin indicates a fault when one occurs in either channel. The FLT signal can be deactivated by toggling the EN input of the faulted channel and sequential toggling of ENx inputs can be used to determine the faulted channel. In versions A, B, C of the device the SNS pin also indicates the fault status of the channel, provided the faulted channel is selected with the SEL pin.

In version D of the device, there are two (FLT1 and FLT2) pin outputs corresponding the presence of a fault in each channel. The independent FLTx signals can be used to easily determine the faulted channel. The FLTx signal is deactivated by toggling the EN input of the faulted channel. In version D of the device the SNS pin does not indicate the fault status of the channel, just the load current sense.

Table 9-4 shows the states for both the SNS pin and the FLT pins based on the fault states and ENx/SEL pin state (applies to versions A, B, C). By looking at these pins, it is possible to detect where the fault has occurred. The method to identify the channel that caused the FLT signal is as follows when an MCU is monitoring the SNS pin output. If the SNS is signaling a fault (with I_SNSFH current output) while SEL=LO, then the fault is in channel 1, whereas with SEL=HI, the fault is in channel 2. If SNS pin signals fault with SEL at either LO or HI, then both channels are faulted. As discussed earlier, the type of faults (whether it is overcurrent, overtemperature or open-load) can be determined by the state of EN input in each channel. If the SNS pin output is not monitored, it is still possible to identify the channel that is faulted. To do this, the EN pin in each channel must be toggled (LO to HI or HI to LO as the case can be). If the fault indication on the FLT pin is removed by toggling the EN input in a channel, then the fault is in that channel. If the fault indication does not go away with toggling EN input of both channels, then the fault is in both. The time duration for toggling the EN input must be kept below 10 us to ensure that there is no impact on the actual output of the channels.

While typically the SNS pin output corresponds to I_LOAD, in a fault case the switch turns off and I_LOAD goes to zero so the SNS behavior is modified in a fault case. In the event of a fault cases where SEL is monitoring the proper channel, the SNS pin outputs a voltage level corresponding to the fault type to enable improved diagnosis as shown in Table 9-5.

By looking at the combination of the ENx condition, FLT , and SNS pins, it is possible to distinguish between fault states. Each channel has independent fault states, so the table below applies to CH1 when SEL = LO and CH2 when SEL = HI.

In version D of the device the fault table is shown in Table 9-6. By looking at these pins, it is possible to detect which channel the fault has occurred. As discussed earlier, the type of faults (whether it is overcurrent, overtemperature or open_load) can be determined by the state of EN input in each channel.