New-Tech Europe Magazine | H2 2023

What Are the Critical Roles of Ship Mode and Sleep Mode? The ship mode and sleep mode are the common jargon used in battery operated IoT devices and are crucial aspects of power management in IoT applications. The ship mode is a nanopower state that prolongs battery life during the shipment stage of a product. In ship mode, the battery is electrically disconnected from the rest of the system to minimize power drain while the product is idle or not used. Push-buttons are used to release the ship mode and start the normal operation of the device. Once the device is in an active condition, sleep mode is used to extend the battery life. In sleep mode, all the peripherals of the system are either shutdown or operating at their minimum power requirement. IoT devices wake up periodically, perform a specific task, and then return to sleep mode. Different sleep modes can be achieved by disabling various peripherals of the wireless sensor node. For example, in modem sleep, only communication blocks are disabled. In light sleep mode, most of the blocks including the communication block, sensor block, and digital blocks are disabled, and, in deep sleep mode, the wireless sensor node is completely powered off. Enabling the deep sleep mode in the sensor node can maximize the battery life; therefore, optimizing the deep sleep current is the only way to improve the overall battery life. The Duty Cycling Method to Enable Deep Sleep Mode in IoT Applications Duty cycling in the IoT module is one of the popular techniques for enabling the deep sleep mode. While a wireless sensor node is in deep

Figure 1: The typical building blocks of an IoT system. Credit: Analog Devices

The Conventional Solution for Deep Sleep Mode and Ship Mode: Using an RTC, Load Switch, and Push Button Controller In the conventional solution, a load switch and an RTC are used to power on/off the wireless sensor node. In this approach, only the load switch and RTC are active, decreasing the total quiescent current to nanoamperes. The sleep time can be programmed with the microcontroller inside the wireless sensor node. An external push-button controller

sleep, most of the peripherals are off or in shutdown mode, consuming only new nanoampere current. A time-keeping device like the real time clock (RTC) will wake up the IoT module after a programmed timeout. In this technique, the microcontroller is completely off while the system is in deep sleep mode. However, after recovery, there is always a start-up boot time involved that will add an undesirable delay. Given this trade-off, the impact of the proposed principle depends on the characteristics of each node and the duty cycle of the application.

Figure 2: A discrete solution block diagram. Credit: Analog Devices

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