A brief analysis of three ways to achieve low power consumption in MCU

　　Today's electronic products have higher and higher requirements for low power consumption. The problem of product power consumption is a problem that often gives product designers headaches but has to face. The power consumption of a system with a single-chip microcomputer as the core is mainly composed of the power consumption of the single-chip microcomputer and the power consumption of the single-chip microcomputer's peripheral circuits. To meet the low power consumption requirements of the single-chip microcomputer system, it is easy to choose a single-chip microcomputer with low power consumption characteristics. Because a single-chip microcomputer with low power consumption characteristics can greatly reduce the power consumption of the system, this can be examined from the power supply voltage, internal structure, system clock and low power mode of the single-chip microcomputer. In order to minimize the power consumption of the controller. There are roughly three ways to achieve it: reducing the power consumption in the working mode, reducing the power consumption in the sleep mode, and shortening the wake-up time from sleep to work.

　　Reducing power consumption in working mode is the first task to be overcome, and most manufacturers that have launched low-power MCUs have already done it. The biggest problem is that lower system frequency or operating voltage must be used to save power, but it cannot affect the performance of the product. Integrating power management is a good method. Mike Salas, director of microcontroller product marketing at Silicon Labs, a manufacturer with a focus on this field, said that integrating a proprietary DC-DC converter can reduce the operating voltage of the operating mode to 0.9V, so that the same function can be used with only one battery instead of two batteries.

　　MCU can be divided into two types according to its memory type: the type without on-chip ROM and the type with on-chip ROM. For the chip without on-chip ROM, an external EPROM must be connected to it for application (typical chip is 8031). The chip with on-chip ROM is further divided into on-chip EPROM (typical chip is 87C51), MASK on-chip mask ROM (typical chip is 8051), on-chip FLASH (typical chip is 89C51), etc. Some companies have also launched chips with on-chip one-time programmable ROM (One Time Programming, OTP) (typical chip is 97C51). MASKROM MCU is cheap, but the program is solidified at the factory, which is suitable for applications where the program is fixed; FALSHROM MCU program can be repeatedly erased and written, which is very flexible, but the price is higher, which is suitable for applications that are not sensitive to price or for development purposes; OTPROM MCU price is between the first two, and at the same time has one-time programmable capability, which is suitable for applications that require both flexibility and low cost, especially electronic products with constantly updated functions and need to be mass-produced quickly.

　　As for power control in sleep mode, the industry consensus can be divided into two directions: lowering the minimum power consumption in sleep mode and providing different levels of standby mode. Yang Zhenglian, product marketing manager for Greater China and South Asia at STMicroelectronics, said that today's low-power MCUs can dynamically adjust to different power-saving modes, automatically shutting down unnecessary functions according to different usage conditions, with the lowest power consumption of only 0.27A, which is almost impossible to detect with an electric meter.

　　From the perspective of terminal products, low-power MCUs are needed. Many of them are in a long-term dormant state, but as soon as they need to work, they must quickly stand up and start working. The simplest example is a smoke detector. From the perspective of the MCU's own design, if the transition time from dormancy to operation is too long, it means that the current consumption during the waiting period is wasted.

　　Mike Salas emphasized that the three elements of reducing power consumption are all important, but the most important thing is to advance them simultaneously to achieve the best results. Yang Zhenglian also said that maintaining ultra-low power consumption during sleep is important, but in addition, it is also necessary to wake up quickly, complete the work with the lowest power consumption, and then return to sleep at the fastest speed; only in this way can the power consumption of the overall system level be minimized.