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AD7492CB 数据表(PDF) 2 Page - Analog Devices |
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AD7492CB 数据表(HTML) 2 Page - Analog Devices |
2 / 14 page EVAL-AD7492CB –2– REV. A reference are also decoupled to AGND with a 10µF tantalum and a 0.1µF ceramic capacitor. The AD7492 AVDD supply pin is decoupled to AGND with 10uF tantalum and 0.1µF multilayer ceramic capacitors. The AD7492 DVDD and VDRIVE pins are decoupled to AGND with 10uF tantalum capacitors and to DGND with 0.1µF multilayer ceramic capacitors. Extensive ground planes are used on this board to minimize the effect of high frequency noise interference. There are two ground planes, AGND and DGND. These are connected at one location close to the AD7492. Analog Input Section The analog input section of this evaluation board accommodates unipolar and bipolar signals. Unipolar signals within the AD7492 analog input signal range of 0 V - 2.5 V are connected via SK1. They are then buffered by the on-board buffer before being applied to the VIN pin of the AD7492. Bipolar signals are connected via SK3 and are biased up by the on-board bias- up buffer circuit before being applied to the VIN pin of the AD7492. The input impedence of the bias-up circuit is 50 Ω which is determined by the value of R7. The input impedence may be modified by removing/changing the value of R7. To obtain optimum performance from this evaluation board the use of an impedence matched, passive filter is recommended before the analog signal is applied to the evaluation board. For example, when using a 100KHz input tone, a 100KHz 50 Ω filter from TTE (part number KC5-100K-15K-50/50-720B) is suitable. R13 Potentiometer (50Kohm) This variable resistor is used to trim the DC bias voltage applied to the optional analog input bias-up circuit. This bias voltage is factory preset to 1.25 V which biases a bipolar signal to swing around the midpoint of the analog input range (0 - 2.5 V). If any adjustment is required, the user can use the histogram window in the eval-board software to analyze the DC voltage variation while adjusting the trim pot. To view this properly, an analog input signal should not be applied to the board. Under normal operation this pot should not be adjusted as it is preset for optimum performance. LINK AND SWITCH OPTIONS There are 12 link options which must be set for the required operating setup before using the evaluation board. The functions of these options are outlined below. Link No. Function. LK1 This link is used to select the DC bias voltage to be applied to the optional Vin bias-up circuit. If the user is using the bias-up circuit, this link must be inserted which will apply the 2.5 V reference voltage to the bias-up circuit. This causes a bipolar signal (applied to the bipolar vin input socket) to be biased up around +1.25 V before it is applied to the AD7492 VIN pin. - see also LK10 (below). When this link is in position "A" the bias-up circuit is supplied by the AD7492 internal reference. When this link is in position "B" the bias-up circuit is supplied by the AD780 external reference. If the bias up circuit is not being used this link should be removed. LK2 This link must be in position "A" if external power supplies are being used. In this position the control logic is being powered by the voltage applied to the VDD input. When power is being supplied from the EVAL-CONTROL BRD2, this link can be moved to position "B" if the user wants to drive the control logic from a separate +5 V which is generated on the EVAL-CONTROL BRD2. LK3 This link option selects the sleep mode that the AD7492 can be put into. When this link is in position "A" the part goes into full sleep when low power operation is selected. When this link is in position "B" the part goes into partial sleep when low power operation is selected. LK4 This link option selects the source of the CONVST input. When this link is in position "A" the CONVST input is provided by the EVAL-CONTROL BRD2. When this link is in position "B" the CONVST input is provided via the external socket, SK2. LK5 This link option selects the source of the RD input. When this link is in position "A" the RD input is provided by the EVAL-CONTROL BRD2. When this link is in position "B" the RD input is tied to GND. LK6 This link option selects the source of the CS input. When this link is in position "A" the CS input is provided by the EVAL-CONTROL BRD2. When this link is in position "B" the CS input is tied to GND. LK7 This link option sets the voltage applied to the VDRIVE pin on the AD7492. When this link is in position "A", VDRIVE is connected directly to the DVDD pin. When this link is in position "B", an external voltage must be applied to the VDRIVE pin Via J3. LK8 This link selects the source of the VDD supply. When this link is in position "A" VDD must be supplied from an external source via J2. When this link is in position "B" VDD is supplied from the EVAL-CONTROL BRD2. LK9 This link selects the source of the VSS supply. When this link is in position "A" VSS must be supplied from an external source via J2. When this link is in position "B" VSS is supplied from the EVAL-CONTROL BRD2. |
类似零件编号 - AD7492CB |
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类似说明 - AD7492CB |
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