ADC1 incorporates a low-reference monitor to detect a low or missing reference. If the differential reference voltage (VREF = VREFP – VREFN) falls below 0.4 V (typical), the low reference alarm triggers (REF_ALM). The low-reference monitor sets the corresponding alarm bit in the conversion data status byte. The alarm resets at the start of each new conversion. Use the low-reference monitor to detect a missing or failed reference voltage connection. Connect a 100-kΩ resistor across the reference inputs to provide the necessary bias. If either reference input is missing or unconnected, this external resistor biases the reference inputs to each other. The low-reference monitor is a fast-responding analog comparator; therefore, transients in the reference voltage may trigger the alarm.