Tyco Electronics’ Circuit Protection business unit sees three major market trends in 2010: the continuing miniaturization and converging functionality of portable electronics, the transition to higher-speed digital connections, and the emergence of new green initiatives designed to reduce energy consumption. In terms of consumer safety and protecting complex circuitry from damage due to overcurrent, overvoltage, or electrostatic discharge (ESD) transients, these evolving trends and technologies present numerous challenges for OEMs and circuit-protection device manufacturers alike.
Today’s convergent devices combine multiple features such as audio, video, and GPS into one multifunction unit. A convergent device, such as a smart phone, has increased functionality that requires high-power output and uses dense, high-energy batteries, which are more susceptible to overcurrent events than conventional batteries. The challenge here is to provide devices that offer a high level of protection in the smallest package possible.
For example, a typical single-cell lithium-ion (Li-ion) battery pack for a mobile phone requires rugged, reliable circuit protection, because these rechargeable packs are particularly vulnerable to damage caused by accidental shorting and abusive or runaway charging.
One solution is to employ a PolySwitch MXP strap device, which helps provide overtemperature protection on charge and discharge as well as redundant overcurrent protection (Fig. 1). The device provides the same hold current as prior-generation strap devices, but is 88% smaller. Additionally, with its 68% lower resistance, it reduces voltage drop during discharge to increase usable battery capacity, which is an important benefit for increasing talk times in mobile applications.
Another example of meeting the demand for miniaturization and product safety is the femtoSMDC016F overcurrent device. Measuring 1.6 by 0.8 by 0.5 mm, this surface-mount device promises to save space in mobile phones, MP3 players, PDAs, and other space-constrained electronics.
We can expect all major OEMs to have USB 3.0 products in volume production by the end of 2010. The new SuperSpeed USB protocol provides higher data transfer rates and power delivery capabilities than 2.0.
The latest specification increases the amount of current that can flow to a USB device from 0.5 to 0.9 A while a new Powered-B connector also allows one USB device to charge another device by supplying up to 1 A. Obviously, the higher current and power delivery capabilities of USB 3.0 intensify the need for more robust circuit protection.
Several new components and coordinated protection solutions address the requirements for hosts, hubs, and Powered-B devices. The PolySwitch device offers a wide range of sizes, voltage ratings, and hold currents that meet the resettable overcurrent protection requirements of USB 3.0 specs. For example, installing a PolySwitch device on the VBUS line of a USB power source limits current in the event of a short circuit, helps prevent overcurrent damage due to a sudden short circuit downstream, and facilitates compliance with UL60950 (Fig. 2a).
USB 3.0 will not support bus-powered hubs and will only support self-powered hubs. Therefore, a power source is necessary to power up all ports of the hub in USB 3.0 applications.
Employing a dc power connector at the input to the hub may require the use of a circuit protection device to help protect hub electronics from damage caused by overvoltage events, from an unregulated or incorrect supply, reverse voltage, or voltage transients. One approach may be installing a PolyZen device and six low-capacitance ESD devices on a typical USB circuit to help provide a coordinated overvoltage solution (Fig. 2b).
NEW GREEN INITIATIVES
Another trend that offers both challenges and opportunities for OEMs is the emergence of unique energy-saving initiatives and technologies, such as the high-rate-discharge Li-ion batteries groomed for green applications such as e-bikes, light electric vehicles (LEVs), and standby power applications.
The challenge in these applications is providing cost-effective circuit protection devices that can provide 30-A and higher hold currents at voltage ratings over 30 V dc. Currently, circuit protection solutions for high-rate-discharge batteries, common to power-tool battery packs, are large, complex, and expensive.
As a market response to this problem, Tyco Electronics is developing the MHP line of high-power dc bimetal protectors. The devices offer a rugged, reliable, and resettable circuit-protection solution that helps battery pack designers and manufacturers optimize space, reduce cost, and enhance product safety.
To further address these trends as well as other emerging issues, circuit-protection device makers should work with other OEMs. Tyco Electronics’ research, design, and application engineering teams are working closely with integrators and OEMs to develop the circuit-protection components necessary to advance a variety of new technologies and support transitioning markets. Approaches on the drawing board include development of new materials, integration of overcurrent and overvoltage protection devices, hybridization, and miniaturization.