During a start-up phase, each corresponding test current is delivered to a corresponding chain of loads of a plurality of chain of loads. Each chain of loads is coupled between a common node and a corresponding output node. Each chain of loads includes N series-coupled loads, where N is an integer greater than one. A maximum voltage is determined from among the output voltages, where the output voltages are the voltages at the output nodes. Also, a minimum voltage is determined from among the output voltages. The maximum voltage from among the output voltages is compared with the minimum voltage from among the output voltages to make a determination as to whether the maximum voltage exceeds the minimum voltage by a threshold. An indication is output based on a result of the determination.