Figure 7-3 and Figure 7-4 show the ALERT pin response to an overcurrent fault with a conversion time of 50 μs for the temperature, shunt voltage, and bus voltage measurements with averaging set to 1. This configuration results in a total conversion time of 150 μs for all three measurements. For these scope shots, persistence was enabled on the ALERT channel to show the variation in the alert response for many sequential fault events. The alert response time can change depending on the value of the current before fault occurs as well as the how much the fault condition exceeds the programmed fault threshold. Figure 7-3 shows the response time for an overcurrent fault when the fault condition greatly exceeds the programmed threshold, while Figure 7-4 shows the overcurrent response time when the fault slightly exceeds the programmed threshold. Variation in the alert response exists because the external fault event is not synchronized to the internal ADC conversion start. Also the ADC is constantly sampling to get a result, so the response time for fault events starting from zero will be slower than fault events starting from values near the set fault threshold. In applications where the alert timing is critical for overcurrent events, the worst-case alert response is equal to 2 × t_{conv_current} + t_{conv_temp} + t_{conv_voltage} + 25 μs. An additional 25 μs is added to allow for background math calculations. This equation does not account for the 1% oscillator tolerance and is only valid for cases where the overcurrent signal is greater than the conversion threshold and noise. The measurement noise is a function of the conversion time. See Section 6.3.5.2 and Section 7.1.2 for additional information.

Figure 7-3 Alert Response Time (Sampled Values Significantly Above Threshold)

Figure 7-4 Alert Response Time (Sampled Values Slightly Above Threshold)