IC Component Selection When Designing Portable Medical Electronic Systems

As people pay more and more attention to their health, personal health monitoring equipment such as portable ultrasonic diagnostic equipment, blood pressure monitors, and blood glucose meters have begun to gain market favor. Medical electronic technology continues to develop, and different medical devices have different technical development trends. Even the same type of equipment will have different technical requirements and development directions due to the specific application of the product. For example, ultrasonic clinical equipment requires high performance indicators such as low noise and wide dynamic range; while portable systems must balance performance and power consumption. In order to meet portability requirements, devices are required to have low power consumption and high integration characteristics. Portable health products are required to maintain good repeatability, and the products must have extremely low drift over the entire operating temperature range, operating voltage, and use cycle.

How to select appropriate semiconductor devices to implement system design to meet the power consumption, performance and price requirements of portable medical electronic products has become a key challenge for medical equipment manufacturers. The advancement of semiconductor technology has greatly promoted the development of medical electronic equipment towards low power consumption, small size and high integration. Semiconductor manufacturers need to comprehensively analyze the specification requirements of specific systems and the importance of different parameters in the system in order to provide cost-effective solutions.

Reduce system power consumption

The block diagram of a general portable medical device. The system requires a large number of functional circuits: from the analog front end that collects sensor output to the display control that displays the results, battery charging, power supply | regulator management, etc. Portable medical devices based on this architecture require low power consumption and a wide operating voltage range (powered directly by the battery). In order to simplify the design and reduce the product size, the device is required to have an extremely small package shape.

In order to meet the system functional requirements, Maxim has developed a variety of products, from data acquisition based on low-power microprocessors to low-power power management circuits that effectively extend battery life. In order to simplify system design, reduce the number of components, and reduce system power consumption, Maxim has launched highly integrated mixed-signal microprocessors, as well as more intelligent battery and power management chips.

Improve measurement accuracy

Portable medical devices need to measure temperature frequently in order to correct the temperature characteristics of the sensor. There are many options for temperature measurement devices, such as thermistors, PN junctions, integrated circuits that provide linear outputs, etc. The choice of device depends on multiple indicators such as size, cost, power consumption, and accuracy. Improving the accuracy of the sensor is the key to improving the design of portable medical products.

Take the blood glucose meter test system as an example. This system uses electrochemical reactions to detect the patient's blood glucose level. The test accuracy is very sensitive to temperature changes. Therefore, it is necessary to measure the ambient temperature to correct the room temperature measurement parameters. In addition, it is also necessary to avoid the instrument working at a temperature beyond the accuracy range limit. This is especially important for portable products because these products often work in hot or cold outdoor environments.

The general system block diagram is also suitable for blood glucose meter measurement. The sensor port is used to connect the blood glucose electrochemical reaction test strip, and the temperature sensor is used to measure the ambient temperature. The sensor can use an external device or a sensor inside the chip, or measure the temperature of both.

Reduce system costs

Single chip temperature sensors are ideal for low-cost applications. To reduce system cost, the chip's internal temperature sensor can be used for calibration to compensate for the external temperature where the glucose sensor is located. The system can use the measured value to correct the sensor temperature to provide an accurate reading. The temperature reading corresponds to the actual junction temperature of the diode and can be used directly for systems that continuously monitor temperature changes. For applications that require the external temperature of the package, the reading needs to be adjusted to obtain a more accurate value.

The key factor in calibration is to ensure that the temperature sensor is measuring the temperature where the glucose test reaction occurs, that is, where the glucose test strip is located. The test equipment should take into account any temperature deviation that affects the accuracy of the product.