Xilinx Virtex-6 FPGA User Manual
Also see for Virtex-6 FPGA: User guideUser guideGuideHardware setup guideUser guide
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12 www.xilinx.com Virtex-6 FPGA System MonitorUG370 (v1.1) June 14, 2010Analog-to-Digital ConverterThe System Monitor ADC has six dedicated pins (see Figure 4). Two of these pins providea dedicated high-bandwidth, differential analog-input channel (VP , V N ). Another twopins are used to access an external reference voltage (VREFP , V REFN ). By using an externalreference device, a reference voltage with a low-temperature coefficient (< 50 ppm/°C) canbe supplied. This voltage is used to provide stable and accurate measurements over a widetemperature range. An internal reference circuit can also be selected by connecting V REFNand V REFP to analog ground (AGND). This internal reference is typically less accurate overa wide temperature range than an external reference. Performance using the internalreference circuit is specified in the Virtex-6 FPGA Data Sheet. For the most accuratemeasurements, an external reference IC is recommended.The remaining analog pins (AVDD and AV SS ) are used to decouple the power supply forthe ADC analog circuits and provide a local AGND return for the ADC circuitry. TheSystem Monitor connection diagrams (using the on-chip and external reference) are shownin Figure 4. For a more detailed discussion of required power supply connections and PCBoard layout, see Application Guidelines, page 45.In addition to on-chip sensors, the ADC is used to digitize external analog signals. There isone dedicated analog-input pin pair and 16 user-programmable analog-input pairssupplied for this purpose. The ADC has a true differential-sampling analog-input scheme,allowing the ADC to achieve a high degree of accuracy when digitizing both on-chip andexternal channels.The ADC accommodates both unipolar and bipolar analog input signals (see AnalogInputs, page 39). The analog-input mode is selected by writing to the System Monitorconfiguration registers (see Configuration Registers (40h to 42h), page 17). In SingleChannel mode, the configuration registers are also used to select the sampling modes ofthe ADC and the analog input channels such as, on-chip sensors and external analog-inputchannels.Temperature SensorSystem Monitor contains a temperature sensor that produces a voltage output that isproportional to the die temperature.Equation 1 shows the output voltage of the temperature sensor.X-Ref Target - Figure 4Figure 4: System Monitor Dedicated PinsADC1.25V ±0.2%50 ppm/°C2.5V – 5VAV DDAVSSVREFPV PVNVREFNVCCAUX(2.5V ±5%)VCCAUX(2.5V ±5%)UG370_04_061009External ReferenceADCAV DDAVSSV REFPVPV NV REFNOn-Chip ReferenceGND Ferrite for HF noise isolation10nF 10nFGND Ferrite for HF noise isolationPackage Pins10nFwww.BDTIC.com/XILINX |
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