The ACS709 is a revolutionary current sensor IC architecture with several new features in an automotive grade thermally enhanced QSOP-24 package, becoming effectively the automotive grade version of the ACS710. The ACS709 employs a unique high speed low noise chopper stabilizer which allows the device to quickly detect and report a fault in less than 2 uS. Additionally, the higher speed operation results in fundamentally lower noise on the output.   The Fast fault threshold is set in the application with external resistors and the fault can be delayed by adding a capacitor to the fault pin. This delay is added for applications where for example motor control monitoring circuitry is far from the actual motor. The problem here is that the parasitic capacitance intrinsic in the longer cables results in an inrush spike every switching cycle. This inrush, while above the fault threshold, is not expected to latch the fault if an appropriate delay capacitor is added in the application.  

The Zero current reference pin can be used as a reference input to an external A/D converter. The purpose of this pin is to help the application in establishing a voltage reference. This reference often saves customers some external components and aids in system calibration.