Microcontroller power management method - Power Circuit - Circuit Diagram

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Nuvoton's NUC1xx series includes models such as NUC101, NUC100, NUC120, NUC130, and NUC140. These are 32-bit microcontrollers (MCUs) with an ARM Cortex-M0 core. Depending on the clock configuration, they can operate at frequencies up to 50 MHz. However, when handling simpler tasks or under light system loads, the CPU doesn't always need to run at its maximum clock speed. In these cases, you can adjust the system clock to reduce the frequency, which helps conserve power.

Another way to save energy is by putting the CPU into Idle or Power Down modes when it’s waiting for new tasks or only needs to perform minimal operations over longer periods. When triggered by specific events or after a certain time, the CPU can wake up and handle those tasks efficiently. Additionally, unused system modules can also be powered down to eliminate unnecessary power consumption. This article explores various power-saving strategies and provides practical examples to illustrate how these methods work in real-world applications.

Switching System Modules

In the Nuvoton Technology NUC1xx series, one effective way to save power is by disabling the clocks of unused system modules, effectively turning them off and reducing overall energy usage. Almost every module in the NUC1xx can be individually powered down when not needed. These modules include the Watchdog Timer, Real-Time Clock (RTC), Timers 0-3, I2C0-1, SPI0-3, UART0-2, PWM0-7, CAN, USB, ADC, ACMP, PS2, PDMA, and Flash ISP. Notably, some modules like CAN are only available in higher-end models such as the NUC130 and NUC140. For detailed information about each model’s capabilities, refer to the respective datasheets.

The power consumption of each module varies significantly, as illustrated in Table 1 below:

Nuvoton Technology achieves efficient power management in the NUC1xx series by selectively disabling the clocks of individual modules. To shut down any given module, the corresponding clock control bit must be configured appropriately. The NUV1xx provides two key registers for managing this process: the AHBCLK Register and the APBCLK Register.

System Clock Settings

The power consumption of the NUV1xx microcontroller is closely tied to its operating clock speed. Higher clock speeds result in greater power consumption, while lower speeds offer better energy efficiency but may limit the processor’s ability to handle complex tasks. To strike the right balance between performance and power savings, users should configure the CPU’s operating clock dynamically based on their specific requirements, ensuring optimal operational efficiency.

The NUC1xx incorporates a built-in Phase-Locked Loop (PLL) that generates system clocks using either an external 12 MHz crystal or an internal 22 MHz oscillator. The output from the PLL can then be divided down to serve as the CPU’s operating frequency. Alternatively, the CPU can directly receive its clock signal from an external 32 kHz crystal or an internal 10 kHz oscillator. This design gives developers significant flexibility when configuring the microcontroller’s operating clock.