What is a Power Management Unit?

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  • Written By: Malcolm Tatum
  • Edited By: Bronwyn Harris
  • Last Modified Date: 04 October 2019
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The power management unit, or PMU, is a type of microcontroller that is associated with the configuration of computers manufactured by Apple. Essentially, the power management unit controls the power functions on the computer. Currently, all Apple computers make use of a power management unit.

It is helpful to think of the power management unit as a very powerful microchip. Within the context of the function of an Apple computer, this microchip covers the functions supported by other types of components in other brands of computers. Some examples would include software, firmware, and memory capacity. Along with these three key components, a power management unit also provides for analog to digital conversion functions and even includes a CPU.

This broad range of support allows the power management unit to coordinate a number of essential tasks that keep the computer operational. For example, the PMU will constantly monitor the status of any power connections that are presently engaged. At the same time, the unit will monitor the status of the battery and initiate charging automatically if needed. The status of various system components is evaluated on a recurring basis, allowing the power management unit to shut down any component that has been idle for a significant period of time.


The power management unit is somewhat sensitive to sudden changes in power. For example, if the battery is in use and is allowed to run down, this may impact the function of the unit. In like manner, plugging a power cord into an outlet and then plugging the cord into the computer may cause the unit to malfunction. For this reason, users should read the operations manual thoroughly and avoid actions that could negatively impact the performance of the unit.

As with any type of computer component, it is possible for a power management unit to become corrupted. Some common signs that the unit is not functioning correctly would include a failure to initiate a recharging session for the battery or an inability to recognize devices connected to a USB port, such as a jump drive or a printer. In some cases, simple resetting the power management unit will clear up the problems. However, if the reset does not work, there is a good chance that the unit will have to be replaced.


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