For fast-growing markets such as wearable devices or Internet of Things (IoT), energy collection can greatly increase battery life and even achieve cell-free design. But the engineers will face great restrictions when designing can wear equipment or Internet of Things devices, that is, the overall design size and base surface are small. In order to meet the growing miniaturization system requirements, designers can turn to many highly integrated energy collection ICs and wireless MCUs, semiconductor manufacturers who manufacture such devices include: Atmel, CSR, FreeScale Semiconductor, Adi Technology, Maxim Integrated, NXP Semiconductor, Silicon Laboratories, StMicroelectronics, and Texas Instruments, etc.
Energy collection technology can bring enormous advantages to the use of environmental energy applications. The designer has adopted energy collection technology to provide power from the application from the motor and engine monitor to the track electronic component. Generally, such applications are based on built-in wireless sensor design, send sampling data regarding environmental or interest events to controllers, agglometers, or other hosts (Fig. 1).
However, different from other energy collection applications is that wearable devices and IOT devices have a common design requirement to packed basic functions into the most likely small package. Today, designers have multiple options to reduce the base surfaces and overall sizes of these designs. For example, for a simple IoT localization application, a dynamic NFC / RFID tag such as STMicroelectronics M24LR16E can achieve a large number of required features in size of only 4.9 x 6.0 mm.
For a general RFID tag, M24LR16E is powered by itself by collecting radio frequency energy from a radio reader or a nearby coupled device (VCD). However, different from most RFID tags, M24LR16E also has energy collection analog output, which can be used to power the additional devices like the MCU. When set to energy collection mode, M24LR16E-R will output the remaining energy of the collected self-radio frequency field to the VOUT analog pin. Moreover, the designer can modulate the load on the received carrier using the device to communicate with the VCD device, and the rate is up to 53 kbps so that a separate wireless RF transceiver is no longer needed.
Compact solution
However, many IOT applications and most of the design of wearable devices require relying on environmental energy and traditional wireless connection. For this type of design, dedicated IC provides a complete key subsystem solution, including energy collection, sensor data acquisition, and wireless communication. After using highly integrated devices, engineers can reduce energy collection design, with only two of three ICs and minimal discrete passive components to realize size-level solutions for volume, functional complex.
The core of these solutions is a dedicated energy collector, such as the Adi Technology LTC3588-1 and Maxim Integrated Max17710. These devices integrate multiple devices and functions such as DC / DC converters, power management circuits, control functions in ultra-thin, super flat packages. These devices are readily connected to the MCU, only a few external components can provide a complete energy collection power supply for MCUs and other circuits (Figure 2).
The ADI LTC3588-1 can be directly connected to a piezoelectric or other AC power supply, which combines a low-loss full-wave bridge rectifier with a high-efficiency buck converter. Therefore, the device can rectify the AC voltage waveform, store the collected energy into the external capacitor, and then provide a regulated output. In contrast, the Maxim MAX17710 uses a boost regulator controller to generate electricity from a low to 1 UW. The MAX17710 can also be charged from the energy source of the lower to 0.75 V, and protect the battery using an internal regulator to prevent overcharge.
Integration
The designer can complete the wearable device and IOT using a single-chip energy to collect power and a variety of devices that combine MCU kernel with rich filmmile functions (including analog-to-digital converter (ADC) for data collection). Design. Although integrated analog peripherals have been solved, a class of wireless MCUs can be distinguished from the intermodulating integration of wireless connection full range of frequency transitions. It is also important that these devices have achieved impressive ultra-low power consumption and can provide high-precision data conversion capabilities and sufficient TX power and RX sensitivity for these applications. For example, like the Silicon Laboratories Si1004 wireless MCU, a 8051 compatible microcontroller kernel is combined with a piecemade memory, a 10-bit ADC, dual comparator, and film-loaded RF transceiver, which can provide + per second. 13 or +20 DBM maximum emission output power - all of this packaged in a 42-pin LGA package in a 5 mm x 7 mm.
For many of these dedicated low-power devices, Si1004 has a plurality of low power operating modes. The active mode power consumption of the device in the Silabs Si10xx series is only 160 μA / MHz, and the sleep mode current in the internal RTC is only 300 NA. In addition, the Si1004 includes an internal DC / DC switching boost converter that allows the operating voltage to fall to 0.9 V. This internal DC / DC converter provides a programmable output voltage range of 1.8 to 3.3 V, which provides a voltage regulator power of 65 mW to other devices in the system, and even more than 100 mW in some applications. For sensors and other circuits, such additional power supplies can increase connection flexibility if the required voltage is higher than some energy collection applications.
The wireless MCU like Silabs Si1004 can be designed to simplify the connection of the antenna. In fact, Si1004 can be used in TX / RX direct connection, there is no need to use TX / RX switches (Figure 3) for applications that require improvement of performance such as multi-diameter fading, designers can use to integrate to Si10xx wireless MCU The antenna diversity support function in the EZRADIOPRO® transceiver will increase the wireless performance to 10 dB.
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For applications that require higher performance, designers can find a wide range of powerful wireless MCUs, providing support within the wide operating frequency and connection protocol. For example, the CSR CSR1011 supports low-power Bluetooth (BLE), while the Freescale Semiconductor MKW22D512V and NXP Semiconductor JN516x serves 802.15.4 zigbee.
Other devices in this category provide a highly comprehensive transceiver function, such as the Wi-Fi on the Texas Instruments Simplelink CC3200 network processor. The CC3200 combines this network processor module with the high performance ARM Cortex-M4 MCU in a compact 9 mm x 9 mm and 64 feet.
The higher the kernel performance, the higher the power requirements, but the CC3200 can operate at a low power depth sleep mode as low as 120 μA - a dominance in the general wireless sensor application. Designers who concerns worry can also turn to wireless MCUs based on ARM's highest power efficiency kernel Cortex-M0 +, such as Atmel ATSAMR21E18A.
Conclusion
Can wearable and IoT applications require compact design to achieve complex functions at the lowest power requirements. With a special energy collector, the designer can achieve both environmental energy to design power, and do not give up the principle of minimal design size. Highly integrated energy collection IC plus low-power wireless MCU enables designers to implement intact wireless sensor design in tiny systems to achieve complex functions while extracting electrical energy from ambient energy source.
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