Dallas, Tex Dallas Semiconductor has integrated precision A/D converters into its new MAXQ3120 16-bit microcontroller with an eye toward electricity metering among other demanding analog applications.
The device is powered by a high-performance single-cycle execution, 16-bit RISC core, approaching 1MIPS/MHz. It uses an intelligent clock-management scheme that minimizes digital switching noise. Its integrated single-cycle multiply-and-accumulate (MAC) module provides a powerful signal processing function for the microcontroller.
The MCU has two 16-bit sigma-delta analog-to-digital converters, each with independently programmable gain amplification (PGA). This microcontroller also integrates a digitally trimmable real-time clock (RTC), an LCD controller, and a single-cycle multiply-and-accumulate (MAC) module. The device is aimed at demanding analog applications such as electricity metering, medical instruments, portable data acquisition, weight scales, industrial sensors, and controls.
The integration of high performance signal-processing capability and low digital noise enables the MAXQ3120 to acquire analog signals with high precision, and then process them using only a small fraction of its clock-input bandwidth. As a result, customers who incorporate the MAXQ3120 into their end equipment can offer more functionality at a lower cost.
Microcontrollers traditionally have been the most widely deployed as an interface and control mechanism between the digital domain, where control decisions are made, and the real world of analog signals. However, today's designers are increasingly facing more applications that also require precision analog-to-digital conversion and processing in real time. The need to support more complex displays and communication interfaces is also rising. Examples of such demanding, complex feature sets are found in environmental monitoring, electricity metering, medical instrumentation, portable data acquisition, and industrial sensors and controls.
Although electricity meters are ubiquitous in our modern world, achieving accurate electricity metering is no easy task for meter designers due to the inherent requirement for high precision and wide dynamic range analog-to-digital conversion. Compounding the challenge are the needs for advanced communication capabilities and keeping accurate energy accumulation in different time periods. Time is literally money for both the consumers and the electric utility companies!
The traditional microcontroller design solution was to interface discrete high-precision analog components, display, and communication devices with a microcontroller. In a typical multitariff (time-of-use) electricity meter today, for example, one will find these critical devices: ADCs with fixed-function DSP for energy accumulation; an LCD driver; an RTC; a microcontroller; and perhaps a communication module such as an RS-485, RF, or powerline modem.
Designing-in and sourcing these many components from multiple vendors poses many challenges to the integrating manufacturer. This design challenge is especially compounded when a project is constrained to a very small physical box and tight budget. MAXQ3120 helps solve the challenges by integrating most of the key discrete components into a single chip: a microcontroller, a digitally trimmable RTC with its dedicated battery-backup power supply, an LCD driver that supports up to 112 LCD segments, two universal synchronous-asynchronous receiver/transmitters (USARTs) ports to support two simultaneous communication channels, two differential high-precision ADCs with programmable gains, and a high-performance single-cycle MAC. With the single-cycle MAC, energy accumulations can be computed quickly without taking much of the input clock bandwidth, and still keep the device responsive enough for other tasks such as communication and metering data display.
The MAXQ cores (including the MAXQ20 in the MAXQ3120 microcontroller) distribute clocks only to the paths where the clock is needed, thus achieving much lower switching noise compared to other architectures. The MAXQ is a non-pipelined, true single-cycle execution architecture with a data-processing speed approaching 1MIPS/MHz.
The hardware multiply-and-accumulate module of MAXQ3120 allows it to perform digital-signal-processing (DSP) algorithms with ease, even in data-intensive applications. The MAXQ3120 takes, for example, only about 2.7MIPS (or 33% of a 8MHz input clock) to process and manipulate all the data in a multifunction single-phase electricity meter. This is especially impressive when one realizes that, in this short interval, both voltage and current inputs are digitized into two streams of 16-bit values, while the active and reactive energies and the voltage channel's RMS value are computed at every data conversion. This activity still leaves 5.3MIPS for other tasks. To emphasize the magnitude of this MAXQ3120 accomplishment, note that this remaining 5.3MIPS is equivalent to the full speed of most popular 20MHz, 4-cycle microcontrollers. MAXQ3120 also allows a customized low-pass filtering to be applied in order to optimize the ADC output for its target application. With the help of the integrated fast single-cycle MAC, this programmable filtering capability makes MAXQ3120 very attractive for a wide variety of signal-processing applications.
A preliminary Data Sheet is available at www.maxim-ic.com/maxq3120.
The MAXQ3120 is packaged in an 80-pin MQFP, and operates over the -40 degrees C to +85 degrees C temperature range. MAXQ3120 reference designs are available to help customers shorten design time-to-market. Prices start at $4.08 (1000-up, FOB USA).
Dallas Semiconductor, 1-800-998-8800