In a general aspect, a circuit can include a reference current generator configured to generate a first current signal representative of a threshold voltage. The circuit can also include a current comparator configured to mirror the first current signal, generate a second current signal representative of a received voltage and compare the second current signal to the first current signal. The current comparator can also be configured to provide a detection signal at a first logic value to indicate that the received voltage is below the threshold voltage when the comparison of the second current signal with the first current signal indicates that the received voltage is less than the threshold voltage.