Renesas H8/300H Super Low Power (SLP) devices are small, use extremely low consumption of power, and apply the analog IP essential for various measurement applications.

An increasing volume of information about health matters can be seen in information channels such as magazines, newspapers, and TV. Across the globe, the issue of health is changing from something you respond to when a problem arises, into something that you proactively manage and foster. As a result, demand has been growing rapidly for personal healthcare monitoring devices such as blood-pressure meters, body-fat monitors, glucose meters, and pedometers that make it easy to regularly check on the condition of your body and the health of your family. Conveniently compact portable products abound, many of which are microcomputer-based systems powered by batteries.

Another type of monitoring application that is experiencing fast growth is utility meters ? especially electronic implementations with microcomputers that periodically measure the usage of electricity, gas, and water in households and elsewhere. For service providers, such meters have the important advantage that readings for billing purposes can be collected remotely at a monitoring station, rather than by employees who have to go to sites to record the data shown on a meter's dials or display.

Healthcare devices and utility meters have two characteristics in common: the core function in each case is measurement, and both types of devices require similar technology and performance. Specifically, they must operate without maintenance for long periods of time, be compact, and provide the analog intellectual property (IP) needed to enable good measurements to be made using analog sensors.

■ Very low power consumption

Battery-powered healthcare monitoring devices and utility meters require system designs based on microcomputers that use minimal amounts of power ? levels that are among the lowest of any type of electronic equipment. For example, portable pedometers and blood-pressure meters typically must operate for years powered only by button-type or AA-size batteries, and gas meters have to run for a decade or more on a single lithium-ion battery.

■ Small size

One reason for the rising popularity of personal healthcare devices is the fact that they are conveniently portable and compact. They use microcomputers in "ultra" small size packages, devices with built-in peripheral functions that minimize the need for external components.

■ Analog IP

Analog signal processing capabilities must be incorporated into the microcomputers used in monitoring devices and meters. Among the on-chip peripherals essential for many of these applications are analog-to-digital (A/D) converters (also called ADCs), power-on reset (POR) and low-voltage detection (LVD) functions, and high-precision clock oscillators.

Renesas applies advanced semiconductor technology to meet the requirements of embedded systems. For healthcare monitors and metering applications, we take full advantage of our library of IP. Specifically, we apply our expertise in techniques for reducing the power comsumption by the microcomputer and entire system, integrating analog functions into the chip, and producing devices in very small packages.

■ Ultra-low power consumption technology

Products such as portable healthcare monitors and gas and water meters consume much more current when they are operating ? making measurements and processing data ? than they do when they are in standby mode. Typically, the ratio of the power comsumption when the microcomputer is running application code is about nine times the current used when the device is in standby mode with only the clock operating; that is, typically the ratio is about 9:1. Despite this fact, the current consumed in standby mode is more important than the current in the operating mode because in most cases the system spends the vast majority of its time in standby, waiting to take the next measurement.

Microcomputers in the H8/300H Super Low Power (SLP) series in the H8 family employ ultra-low power consumption technology and deliver the performance needed to reduce current draw to low levels that allow extended battery life. With just the clock running in standby mode, they consume only 2.0μA at 3.0V. Further, their minimum operating voltage is 1.8V (reading). Models are available with memory sizes between 8KB and 128KB.

■ Low-power comparator

To reduce power consumption, a monitoring or metering system can be designed to use a low-power comparator to monitor an external analog signal. Only when the comparator indicates that the voltage has changed does the CPU turn-on the A/D converter so it can read the new signal level (see Figure 1). This technique is particularly effective when the comparator is a very power-efficient implementation, like a design contained in our analog IP library. Built into the microcomputers in the H8/38602R group in the H8/300H SLP series, for instance, this comparator consumes only 2.0μA at 3.0V.

■ 14-bit ΔΣ-type A/D converter

Devices in H8/38086R group in the H8/300H SLP series provide a 14-bit ΔΣ-type A/D converter, an analog IP that we believe was the first of its type integrated into a general-purpose Japanese microcomputer. This A/D achieves power savings in several ways (see Figure 2). It does not require an amplifier, as other types of A/Ds do, nor does it require a range-switching circuit to interface to signals spanning a wide range of peak voltages. (The latest, higher resolution version of this A/D is described in another story in this magazine:"16-bit ΔΣ-Type A/D Converter Enables Precise Measurement.")

■ Ultra-small packages

Space is in short supply in compact healthcare products and meters, and Renesas aids miniaturization efforts by manufacturing H8/300H SLP microcomputers in ultra-small packages. Choices for situations requiring high mounting densities include a 32-pin, 5mm x 6mm QFN (0.5mm pitch); a 64-pin 8mm x 8mm QFN (0.4mm pitch); and an 80-pin 7mm x 7mm LGA (0.65mm pitch) (see Figure 3).

To be successful in competitive markets, healthcare-monitoring devices must be easy to use and relatively low in cost. Thus, besides offering the features previously described, the microcomputers in them must be relatively inexpensive microcomputers and have CPU cores with good computing capabilities. The devices that Renesas currently recommends for new designs for these applications and for utility meters are the 16-bit microcomputers in the H8/38602R and H8/38086R groups mentioned above.

■ Microcomputers in the H8/38602R group

Members of the H8/38602R group are ultra-small, ultra-low-power-consumption microcomputers. They have a tiny ? 5mm x 6mm ? 32-pin package, and draw very little current: only 0.5μA at 1.8V in standby mode on the clock. When they are combined with acceleration, temperature, pressure or other types of analog sensors, they can save power by using a very-low-power on-chip comparator to watch for changes in the sensor's signal before triggering an A/D conversion, the technique previously described. Due to their exceptional power efficiency, these devices have been widely adopted in sensor units for industrial and consumer equipment.

The left side of Figure 4 shows the block diagram of an H8/38602R microcomputer. Figure 5 shows a pedometer system implemented by a device in this product group.

■ Microcomputers in the H8/38086R group

Members of the H8/38086R group have 80-pin packages as small as 7mm x 7mm. They provide the internal 14-bit ΔΣ-type A/D converter that eliminates the need for an external high-resolution A/D chip. These microcomputers also have a built-in LCD driver for displaying measurement results. They are ideal for measurement devices and other applications that require high mounting density.

The right side of Figure 4 shows the block diagram of an H8/38086R device. Figure 6 shows a measurement system that applies the microcomputer's on-chip ΔΣ-type A/D. Figure 7 shows some measurements made with that system.

It is clear that healthcare monitoring devices and utility meters will continue to mandate low power consumption, integrated analog technologies, and small package sizes. It's also true that these applications are not the only ones with growing demand for these features. Renesas intends to continue providing timely solutions that meet the needs of global markets with microcomputers in our H8/300H SLP series, SuperH family, and R8C/Tiny series, among others.