Circuit protection of wearable technology in medical market

- Apr 22, 2017-

Fortunately, the wearable technology incorporated into the physiological sensors is increasingly appearing in our lives. A new generation of monitoring devices can be worn on the body, users no longer have to be forced to instruments (such as blood glucose meter) into the pocket to carry. These medical sensors are almost transparent, so that people will be close to real-time monitoring of their own state, so that they accumulate more data points in the course of the day.

Various examples have now appeared on the market. This method is used to measure including walking distance, pulse and other data wristbands, designed for physical training when using unobtrusive underwear, can collect parameters such as pulse, respiratory frequency, position and distance data etc..

Obviously, the development and adoption of these new technologies is expected to improve data collection, and ultimately benefit the health of users. However, these systems will eventually be worn close to the skin that is its biggest advantage, but also its potential weakness, the reason is that they will always be exposed to static user self generated, without proper protection conditions can make the fault. Unfortunately, sometimes only a touch can cause a static discharge transient. Any sensor circuit, button, battery charging interface, or data output / input port can provide a path for electrostatic discharge into the wearable device.

Fortunately for wearable device manufacturers, the ESD protection component based on semiconductor technology is making unremitting efforts to improve the capabilities of these solutions. Electronics companies continue to invest in the development of new processes to improve the performance of their protection products. The latest component innovation technologies include:

Reduce the clamping voltage, protect the most sensitive circuit: in the event of electrostatic discharge, the main work of electrostatic discharge protector is to shunt and dissipate as much as possible the electrostatic discharge transient pulse. This property can be improved by reducing the on state resistance. By reducing the dynamic resistance, the transient current of the electrostatic discharge protector will be much higher than the current in the protection circuit. In this way, it reduces the static stress on the integrated circuit and ensures that it is not damaged. For example, a transient voltage suppression diode array with a dynamic resistance value of less than 0.1 can be used to provide the best protection performance.

The lower capacitor, to avoid interference of high-speed data transmission: Although the circuit protection is the main purpose of electrostatic discharge protection devices, but to this effect at the same time, also should not cause interference on the protected circuit operation. In order to ensure the integrity of the signal, the capacitance of the electrostatic discharge protector must be reduced to a minimum without affecting the level of protection.

Smaller size, suitable for wearable devices limited circuit board space: no matter how good the performance of a protective device, if it is not suitable for the application to protect the application, it will not be particularly useful. Wearable medical devices will increasingly thin more and more small direction (watches, wristbands, chest strap etc.) or directly implanted into clothes, therefore, the space will be left for ESD protection solution is very small. Discrete diodes will be the ideal choice for designers to bring excellent board layout flexibility.

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