Dynamic (Software-Controlled) Power Enable/Disable
Dynamic Software Enable/Disable is a feature that refers to the ability to turn a power domain on and off “on-the-fly”. Unlike the sophisticated CMOS digital circuits like CPUs, referred to in the section on Dynamic Voltage Control, many load circuits do not have the capability to self-modulate their power state. These “dumb” loads, such as LED backlights, must be turned off with an independent signal to realize power savings. However the decision to turn off the load is typically made in software. Dynamic Software Enable/Disable bridges the gap between the system software and the load.
Figure 3. (Dynamic Power Enable/Disable)
Summit Programmable Power Managers have a convenient I²CI2C interface by which system software instructions can be sent to the individual power outputs. Outputs are thereby powered up or down with predictable slew rates and timing. This method is illustrated in Figure 3. This is typical example of a portable battery-powered multimedia device with CPU, LCD display with LED backlighting and audio/video powered by an SMB122 – and integrated multi-output power manager IC. The total power consumed by this device (1.95W) is shown on the left with all blocks being enabled (red) – this mode represents a full-power mode where all the functionality of the device is being actively used. The right side of Figure 3 shows a mode where many of the functional blocks (display, backlighting, CPU) have been powered down but audio and memory are still enabled – a typical operational mode for music listening. The blocks that have been disabled are represented in grey and the total consumption has been reduced by about 75% to 0.5W. This “mode-aware” power management algorithm can be easily implemented in a low power I2C controller represented by the “MCU/RTC” block.
If all digital electronic systems used this technology it is estimated the global power savings would be on the order of gigawatts, which represents multiple power generating plants and millions of tons of CO2 emissions each year. Summit Dynamic Power Enable/Disable technology is featured in the following products:
SMB122
SMB120
SMB117
SMB113A
SMB112
SMB111
SMB110
SMM105
SMM205
SMM150
SMM465
SMM605
SMM665
SMM764
SMM766