Renesas' 16bit microcontroller provides on-chip 14-bit analog-to-digital converter.

Renesas Technology America, Inc. recently announced the H8/38086F, an economical 16-bit microcontroller (MCU) with on-chip flash memory, a high-precision analog-to-digital (A/D) converter, and an LCD controller with an adjustable constant-voltage booster. The new single-chip solution is ideal for measuring instruments such as electric power meters, as well as consumer products such as glucose meters that must obtain precise data from analog measurement sensors, yet require low-cost system designs. The H8/38086F MCU is based on a 16-bit H8/300H CPU core and incorporates a delta-sigma type 14-bit A/D converter.

According to Hank Pawlowicz, product marketing manager, system LSI business unit, Renesas Technology America, Inc., "This new microcontroller lets customers address system opportunities arising from two important industry trends. The first trend, in industrial and utility markets, is the rapid increase in the use of electronic versions of electric power meters and water meters. MCU-based designs must be low in cost, be battery powered and have the capability to handle diverse billing modes while helping to prevent fraud. The second trend, in the home market, is the increasing popularity of compact portable diagnostic devices such as glucose meters that make it easy to monitor one's own state of health. Such meters, which measure variations in minute analog signals from sensors and convert them into digital signals, must be more affordable than traditional multi-chip designs built with a sophisticated A/D conversion IC and a microcontroller. Certainly, all of these applications--and many others, too -- can benefit from the low cost, high power efficiency and precision A/D conversion that the Renesas H8/38086F single-chip solution provides."

The H8/38086F is the first Renesas Technology microcontroller to incorporate a delta-sigma type A/D converter capable of high precision at high resolution. A key contributor to the precision is a band-gap reference circuit that generates a very precise and stable voltage that is used as a reference source for signal processing. The 2-channel converter design, which includes a programmable gain amplifier (PGA) and a band-gap reference voltage source, has a 3.0V full-scale range with a typical nonlinearity error of only +/-274microvolts. This error is over 96 percent less than the +/-7.3 millivolt nonlinearity error typical of a conventional successive-approximation type A/D converter with 10-bit resolution. For more cost sensitive applications, Renesas also offers a version of the MCU without the delta-sigma A/D converter (H8/38076).

The H8/38086F incorporates a voltage booster circuit on the LCD controller. In a battery powered system, the voltage supply can be anywhere from 1.8 volts to 3 volts, depending on the battery technology and the amount of unused power in the battery. In a traditional system, a separate voltage booster provides the precise constant voltage needed for the LCD glass. This external device increases system cost and also forces the entire microcontroller to run at a higher voltage, which wastes valuable battery power.

With the constant-voltage booster built into the H8/38086F, the battery and the 3-volt LCD glass can be directly connected to the MCU. The microcontroller can run at a lower battery voltage to reduce power consumption, yet the constant-voltage booster will provide the stable, higher level of voltage required by the LCD glass. Because the output of the voltage booster is adjustable via registers in the H8/38086F, the best possible LCD contrast can be obtained. By eliminating the separate voltage booster, this single-chip solution saves power and system cost.

The CPU core and peripheral functions of the H8/38086F are optimized for lower power consumption, allowing operation down to a low 1.8V. To help maximize battery life, the device offers eight power-down modes, including Active (medium-speed) mode, Sub-active mode, and Watch mode. System designers can achieve the lowest possible current dissipation by performing various kinds of processing only when necessary and then selecting the MCU operating mode most suitable for the specific function the system is performing at a given moment. Power consumption in the Active operating mode is as low as 900 microamperes (typical, at 1.8V/1MHz operation). An ultra-low current dissipation of 0.5 microamperes (typical, at 1.8V/32kHz operation) can be achieved by switching to Watch mode.

Besides the 14-bit A/Ds, 10-bit A/Ds, and the LCD controller/booster, the H8/38086F MCU offers many other built-in peripheral functions, such as power-on reset (POR), real-time clock (RTC), hardware I2C bus interface, several timers and two serial interface channels.