Mixed-signal FPGAs can be a key element of an effective, efficient, in-circuit analog-signal-channel calibration approach By Christian Plante, Director, Fusion Product Marketing, Actel CorporationPlanet Analog (12/04/08, 11:59:01 AM EST)
Today's intelligent system management designs in typical telecommunications or industrial control applications need to constantly monitor several voltage rails and take appropriate action when a certain condition exists. If a high-end telecommunications system must be shut down, for example, it is important that accuracy be very high and the output measurements are carefully calibrated to eliminate errors that can occur in the measurement process. For this reason, these applications need accuracy levels better than 1 percent. However, the total system accuracy offered by most analog-to-digital converters (ADC) signal chains may not sufficient.
In principle, the operation of an ADC is very simple. Given an analog input, it provides an accurate output value in digital format. However, in reality, the accuracy of the output voltage is subject to a number of factors, including gain and offset errors from the ADC and from other components in the signal chain.
Multiple discrete components, such as a pre-scaler or a divider network, have traditionally been used for calibration, to achieve the stringent accuracy and precision levels required by intelligent system management and industrial control applications. An alternate scenario is the use of a feature-rich, mixed-signal field-programmable gate array (FPGA) capable of supporting a calibration scheme, both in software and without the use of external components, to enable easier design implementation, improve accuracy, lower overall power consumption and increase signal integrity.
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