issue: October 2004 APPLIANCE Magazine Electronics Report Mixed-Signal MCUs	Share  Printable format  Email this Article  Search
A new product family of microcontrollers (MCUs) from Austin, TX, U.S.-based Silicon Laboratories is said to feature the industry’s first mixed-signal chip that includes state-of-the-art digital and analog technology on the same chip.

The C8051F064 is reported to offer designers an easy-to-use, integrated solution for appliance applications that require high-speed data acquisition, high accuracy, low noise, and low power consumption. To reduce power system needs and meet critical power system budgets, the MCU integrates dual 16-bit analog-to-digital converters (ADCs) that dissipate only 20 mW per ADC at one-fifth the power of competing standalone ADCs. “Our solution provides designers of embedded applications an affordable programmable solution so they do not have to sacrifice performance for cost or board space,” says Kevin Coffey, product manager for Silicon Laboratories.

One of the most challenging aspects of mixed-signal MCU design is to apply a high-precision ADC on the same die with a high-speed digital CPU and system running at 25 Mhz. “High clock speeds create several fast edges that generate noise, which can interfere with precision analog circuits and affect the accuracy of peripherals, such as the ADC,” Mr. Coffey explains. “Silicon is the first company to integrate a 16-bit successive approximation-type SDC onto an MCU and still achieve excellent signal-to-noise performance that one would expect from standalone components.”

Another feature is the on-chip direct memory access (DMA) controller that can be configured to manage the results of the ADC and transfer them to RAM or parallel port. “Because the ADC runs so fast, it is helpful to have this capability, so that the CPU can concentrate on running the application code or other system functions,” Mr. Coffey notes.

Products in which the C8051F064 can be used are computed axial technology (CAT) scanners, difribulators, EKGs, blood analyzers, and pulse oximeters. The mixed-signal chip can also fit into many other appliance applications. As a controller, the C8051F064 can monitor all of the sensors and execute the control algorithm that sends output signals to motors and other actuators in appliances such as refrigerators and washing machines.

“Appliances that need precise control of motors now have the option of using a C8051F064,” Mr. Coffey says. “For three-phase motor control, it is necessary to measure two-phase currents simultaneously. The F064 has included two separate ADCs, which allow this function to be performed. The high-precision ADC and analog front end also interface cleanly to temperature, pressure, and humidity sensors, with no external amplifier circuits required.”