As consumers are becoming increasingly cautious with rising energy costs, and more and more options for mid- to small scale local power generation becoming available, accurate measurements are practically mandatory. Cirrus Logic’s experience and knowhow in this field is well recognized throughout the industry, with a range of high performance products.

Cirrus Logic concentrates on Analog Front End devices, as wide market research has revealed that each end application has it’s own needs for processing, interfacing and communication. All of the needs on the measurement side are taken care of by the AFE, with a full range of calculations - including Irms, Vrms, Active Power, Reactive Power, Apparent Power - up to the 50th harmonic if necessary, freeing the application processor up for it’s specific tasks. Meaning analog to digital conversion, advanced metering calculations and interfacing to a mechanical counter, stepper motor or MCU are done in the AFE.

The vast diversity of applications means that further integration does not really make sense, as the needs for graphics interface (dot or characters, nr of characters & lines, … ), data transfer (UART, I²C, SPI, …), useable memory size, nr of I/O’s, etc, vary widely. As more advanced wireless communication is moving more and more in the picture as well, often it will be more economical to integrate the application software into the wireless communication processor.

The Cirrus Logic AFE’s offer best in class accuracy in data linearity over the full dynamic range, in this respect that the 0.1% active energy data linearity over a 1000:1 dynamic range is achieved within one single gain stage of the current ADC. Meaning no need for gain adjustment to reach this level of linearity, no loss of accuracy during the transition, nor the need for additional expensive calibration steps in production.

The accuracy is achieved by implementing very high performance 24bit, 4th order delta sigma modulators and by providing dedicated ADC’s for each channel measured. If the ADC channels are multiplexed, the phase relationship between current and voltage are lost, sacrificing overall accuracy of the power calculations.