The power sources of MCU include kernel,peripherals,storage and I/O,etc.This paper introduces the common strategies of power optimization from these perspectives.These strategies and their combinations are the core of MCU's low power consumption mode.Knowing this information can make better use of MCU's low power consumption mode and make power consumption optimization easier.
 

1.Low power consumption of the core

The kernel is a big power consumer of MCU.In practical applications,we often find that not all code needs to run at full speed.Clever use of dynamic frequency adjustment technology to adjust the working frequency of the core in real time according to the task requirements can significantly reduce power consumption.This intelligent speed regulation mechanism,like the constant speed cruise of a car,not only ensures the performance requirements,but also avoids energy waste.
 

2.peripheral low power consumption

The power consumption control of MCU peripheral module needs two-pronged approach.For working peripherals,the clock frequency should be reduced as much as possible on the premise of meeting the functional requirements;For idle peripherals,it is necessary to completely turn off the clock signal and clear the enable bit.This operation can effectively turn off the analog circuit components inside the peripheral and realize deeper energy saving.When the MCU enters the sleep mode,the kernel clock stops,but the peripherals and memory can still run normally.At this time,the reasonable configuration of DMA to realize data transfer between peripherals and memory can greatly reduce the working time of the kernel and further improve the system energy efficiency.
 

3.Low power consumption of the memory

From the point of view of energy consumption,it is more energy-saving for MCU to read instructions from RAM than from Flash.Therefore,transplanting high-frequency code segments into RAM is an effective energy-saving means.It should be noted that different low-power modes handle the memory in different ways:in the stopped state,the RAM content is preserved;When waking up from the standby state,the MCU system needs to reload the program,which will also generate extra power consumption.Developers need to weigh the energy consumption performance of different modes in combination with actual application scenarios.
 

4.I/O low power consumption

Proper handling of unused I/O pins is very important for overall power consumption control.It is recommended to configure idle pins as pull-up/pull-down input or analog input mode to minimize current consumption.For the digital input pin,it is most energy-saving to ensure that its voltage is stable at VCC or VSS level.If the input voltage of MCU is in the middle state,the MOSFET may not be turned off completely,resulting in unnecessary leakage current.The digital output pin of MCU still remains in the output state in low power consumption mode,so it is necessary to pay special attention to check whether the external circuit forms a loop with the internal pull-up and pull-down resistor to avoid continuous current loss.Carefully designed I/O state can often achieve significant energy-saving effect at the system level.
 

By comprehensively using these power optimization technologies,developers can build an embedded system with high energy efficiency ratio,give full play to the low power consumption characteristics of MCU,and bring longer battery life and more stable performance to products.


Keywords: MCU