The maximum before damaging the chip is 17 volts, but it must regulate the voltage down to about 2-3 volts on each LED. This means that it will dissipate heat until it reaches an overtemperature limit, and shuts down the overheating channel. On these boards, the voltage I've had the best results with is about 7.5; with voltages close to 5.5 you will want to have a surplus of amperage capacity to smooth out any power fluctuations.