Today’s wearables demand lower capacitance, lower clamping voltage, and a smaller form factor.
You may have been told not to wear your heart on your sleeve. But now there’s technology that allows you to monitor your heart from your sleeve.
We’re talking about wearable electronics or wearable computing — the hottest consumer electronics sector on the market. Wearable gadgets are interactive devices that often track or monitor information about the wearer. Popular wearables include smart glasses, ring/finger-worn scanners, footwear, wristwear (e.g., electronic watches and wristbands), neckwear, headbands, and the upcoming “smart textiles.”
While it might seem like something out of a science fiction novel, wearables like smart glasses and fitness wristbands are quickly becoming part of our everyday life. According to marketsandmarkets.com, the wearable technology market will be worth $8.36 billion by 2018. That article notes that wristwear accounted for the largest share of market revenues in 2012, with total revenues of the most established wearable electronics exceeding $850 million.
Wearable technology presents an interesting challenge to circuit designers. Why? Think about how these devices are designed to get up close and personal with the consumer. Because they are meant to be worn next to the skin, there’s a significant risk of exposure to user-generated static electricity. Unfortunately, a simple human touch can generate a transient electrostatic discharge (ESD). Without proper protection, any of the sensor circuits, battery-charging interfaces, buttons, or data I/Os could provide a path for ESD to enter the wearable device and cause irreparable damage.
Fortunately, such companies as Littelfuse Inc. are continually investing in the development of new processes that enhance their semiconductor-based ESD protection components. Wearable device manufacturers benefit from an expert supply of circuit protection technologies because they help improve the safety and reliability of their products.
Consider some recent component innovations that can benefit the wearable technology market:
- Lower capacitance to avoid interfering with high-speed data transfer. ESD protection devices must offer circuit protection without interfering with the daily functionality of the circuit being protected. For example, on an RF interface (e.g., Bluetooth or ZigBee) or a wired port like USB 2.0, the ESD protector must not cause distortion or loss of strength of the data signals. To provide signal integrity, the capacitance of the ESD protector must be minimized without compromising protection levels. Littelfuse’s SP3022 Series TVS Diode features a capacitance value of 0.35 pF to ensure that it will remain “invisible” to high-speed signals.
- Lower clamping voltage to protect even the most sensitive circuits. If an ESD event occurs, the primary job of the ESD protector is to divert and dissipate as much of the ESD transient as possible. This characteristic is improved by reducing the on-state resistance or the dynamic resistance. By decreasing the dynamic resistance, the ESD protector carries significantly more of the surge current than the circuit being protected. By doing this, it reduces the electrical stress on the integrated circuit and ensures its survival. For example, Littelfuse’s SP3014 Series TVS Diode Array has a dynamic resistance value of less than 0.1Ω to provide best-in-class performance.
- Smaller form factors to fit the limited board space available in the wearable devices. No matter how well a protection device performs, it’s not very useful if it can’t fit into the application it’s meant to protect. As wearable devices get thinner and smaller, the circuit boards will have minimal space available to accommodate ESD protection solutions. Discrete diodes are the best solution to this potential design challenge because they give design engineers exceptional board layout flexibility. The SP1020 (30 pF) and SP1021 (6 pF) Series Diodes from Littelfuse are contained within the 01005 package outline to minimize the amount of space they occupy. In addition, the SP1012 Series (Figure 1) packs five bi-directional channels of protection in a space-saving 0.94 x 0.61 mm package outline for applications that demand reduced part counts and smaller protection device footprints.
It’s clear that wearable technology is here to stay. Wearable devices will continue to challenge the designers who have to make sure that they function as expected, regardless of the user’s activity level or how often they are subjected to ESD transients. Manufacturers of ESD protection devices will continue developing protection technologies that do not interfere with the wearable device’s core functionality — helping wearable device manufacturers deliver reliability and value to the consumer.