National Semiconductor ADC08100 Instruction Manual

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National Semiconductor ADC08100 Instruction Manual Manual pdf 6 page image

VR2Y1VR1T1U4Q5Q2L4+5VGND+5V-5.2VP1POWER CONNECTORL2L3L1U6Q4Q3TP3AGNDTP3AGNDNATIONAL SEMICONDUCTORADC08100/ADC08200 EVAL BOARDU8 U7 HP1TP5DGNDHP2DL1DL0U5U2U3SocketTP1PDTP9+3VTP8DGNDU1Q1TP4VRBJ1NUM_MEMJ4CLK_SELJ3D4INPUTTP7J2INPUTTP2VRTDIV_ENJ5TP9+3VTP1PDJ1NUM_MEMTP4VRBVR2VRT ADJVR1VRB ADJJ2INPUT BNCTP2VRTTP7INPUTJ4CLK_SELJ4Detail:Default PositionJ5Detail:Defaultis openJ1Detail:Hard-wiredDefault PositionFigure 1. Component and Test Point Locations4.0 Functional Description 4.2 ADC reference circuitryThe ADC08100 Evaluation Board schematic is shown inFigure 2. The provided reference circuitry will provide nominalreference voltage ranges of 1.3V to 2.6V for VRT and 0Vto 1.3V for VRB, Providing for nominal input ranges of 0Vto 2.6V peak-to-peak. Note that this is beyond themaximum specified 2.3V range of the ADC08100.4.1 Input (signal conditioning) circuitryThe input signal to be digitized should be applied to BNCconnector J2. This 50 Ohm input is intended to accept alow-noise sine wave signal of 1.5V peak-to-peakamplitude. To accurately evaluate the ADC08100dynamic performance, the input test signal should bepassed through a high-quality bandpass filter (60dBminimum stop-band attenuation) as even the bestgenerators do not provide a pure enough sine wave toproperly evaluate an ADC.The reference voltages for the ADC08100 can bemonitored at test points TP2 and TP4 and are set withVR1 and VR2. Signal offset can be provided by adjustingboth of these potentiometers, or by minor adjustments tothe +5 Volts at pin 1 of Power Connector P1.4.3 ADC clock circuitThe clock signal applied to the ADC is selected withjumper J4. A standard ECL-level 100 MHz crystaloscillator should be installed at Y1 and the divide by 2function selected by shorting pins 1 and 2 of jumper JP4.Resistors R15, R15A, R16 and R18 provide the neededinput bias to the ADC08100. You can center the inputsignal to the ADC by adjusting reference voltages VRTand VRB with VR1 and VR2 or by making slightadjustments to voltage an Power Connector pin 1.6 http://www.national.com