18. Ferro-Electric RAM Based Microcontrollers: Ultra-Low Power Intelligence for the Internet of Things

Microcontrollers (MCUs) serve a central role in the design of IoT leaf nodes. A typical microcontroller comprises of a processing core, program and data memory, serial communication interfaces, general purpose IO (GPIOs) ports, comparators and ADCs, clock generation and power regulators. Microcontrollers have modest clock frequencies and memory capacities, keeping the IC cost low. High level of integration helps improves performance, lowers power and helps achieve a small form factor. All of these are critical in the design of ICs for IoT applications. This chapter focuses on the design of low power microcontrollers using two Texas Instruments (TI) microcontrollers as examples. Both microcontrollers feature embedded Ferro-electric RAM (FRAM) as a low power non-volatile unified data and program memory. Low write power non-volatile memory with high write endurance (number of write cycles) is critical in IoT applications that feature data logging. FRAM has low power writes at 1.5 V, practically unlimited write endurance (>10¹⁵), and high yields with millions of shipped parts. In the following sections we describe analog, digital and system design techniques that help achieve the low power metrics in TI microcontrollers.