A voltage glitch detector includes a ring oscillator, a plurality of counters, a combined result circuit, and a result evaluation circuit. The ring oscillator includes a plurality of series-connected stages. An output of a last stage of the ring oscillator is coupled to an input of a first stage of the ring oscillator. Each counter of the plurality of counters has an input coupled to a node located between two stages of the plurality of series-connected stages. The combined result circuit is coupled to each of the plurality of counters. The combined result circuit combines the count values received from each counter of the plurality of counters to provide a combined result. The result evaluation circuit is coupled to compare the combined result with a reference value to determine when a voltage glitch is detected.