1.1.3. Dynamic Voltage Controller

The Dynamic Voltage Controller (DVC) is not provided by ARM Limited. It is system-dependent and is consequently the responsibility of the system designer.

The DVC receives the target performance requests from the IEC. It is an AMBA slave (See Figure 1.3 and Figure 1.4). It is required for both closed and open loop control. For open loop control, some of the features of the DVC might not be used. The DVC provides a link to an off-chip PSU.


  • The Advanced Power Controller (APC) from National Semiconductor is an example of such a DVC.

  • The Energy Management Unit (EMU) from National Semiconductor is an example of an optimal PSU.

The DVC receives the required target performance request from the IEC. This performance request is then translated to a voltage level that is communicated to the PSU through an interface such as the PowerWise Interface™ (PWI). The PWI has been developed jointly by ARM and National Semiconductor to provide a high-speed, low-power control interface between an IEM-enabled SoC and an external power supply unit.


  • The DVC provides configuration information to the IEC that indicates the different supported voltage steps. This information is used by the IEC when setting the target performance level.

  • PWI is a standard defined jointly by ARM and National Semiconductor.

For an open loop system, the DVC can either:

If the PSU, such as the EMU provides intermediate stable voltage level indication, then the DVC can also determine this through the PWI.

An example open loop system is described in Open loop voltage control.

For a closed loop system the interface to the HPM determines when the requested voltage, and consequently performance, is achieved. An example closed loop system is described in Closed loop voltage control.

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