Slow changes of power supply voltage do not cause significant disturbances, but rapid changes can make unpredictable trouble. If a voltage exceeds parameters in the controller's data sheet by 150 percent, it can cause the input port or the output port to get hung in one state, known as CMOS latch-up. Without internal current control, latch-up causes the microcontroller to burn out. The standard solution is a mix of software and hardware changes. Most embedded systems have a watchdog timer. This watchdog should be external to the microcontroller so that it is likely to be immune to any plausible electromagnetic interference. It should reset the power supply, briefly switching it off. The watchdog period should be half or less of the time and power required to burn out the microcontroller. The power supply design should be well-grounded and decoupled using capacitors and inductors close to the microcontroller; some typical values are 100uF and 0.1uF in parallel.