MCUs have precise bio-sensing AFEs for healthcare apps

October 06, 2016 // By Graham Prophet
Renesas' RL78/L1A Group of low-power 16-bit microcontrollers with LCD drivers are aimed at battery-powered sensing devices used in healthcare applications such as blood glucose monitors, lactate analyzers, cholesterol analyzers, and other devices equipped with biochemical sensors.

With a built-in analogue front-end (AFE) circuit for biochemical sensing, the RL78/L1A enables blood glucose and haemoglobin measurements with only one monitoring device. The RL78/L1A also delivers improved performance with high precision analogue functions as well as longer battery life. Renesas will also offer Renesas Promotional Boards (RPBs) which allow system developers to immediately evaluate the RL78/L1A functions.

 

It has, Renesas notes, become an industry trend to implement multiple measurement features such as blood glucose and haemoglobin measurements into one monitoring device. However, these features require more complicated system configurations and the burden of developing improved measurement precision and long battery been increasing.

 

Key features of the RL78/L1A Group of MCUs include;

1) Integrated analogue switches allow easy selection of the measurement target, increasing measurement flexibility

The RL78/L1A Group incorporates analogue switches that were previously uncommon in MCU AFEs. By combining switches with a built-in A/D converter, it is possible to switch the measurement circuit including external circuits in software when the target is changed. For example, in devices like blood glucose monitors, adjusting the measurement precision in response to differences in the blood components has become an issue. Flexible methods, such as alternating measurements between components such as hemoglobin and the blood glucose levels, could address these issues.

2) Reference software contributes to improved precision analogue

Renesas provides reference software that makes it easier to improve precision by using the internal AFE functions, such as 12-bit A/D converters, rail-to-rail operational amplifiers, internal reference voltages, and 12-bit D/A converters. In addition to improving device precision, this software can provide improved stability, contributing to improved precision analogue functions in user systems.

3) Lower voltage operation of the analog functions contributes to longer battery life in end products

Renesas has made various circuit improvements to the AFE, enabling a significantly lower supply voltage. These improvements allow the measurement circuit, which is the main function for end products such as blood