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AD5543 数据表(PDF) 11 Page - Analog Devices |
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AD5543 数据表(HTML) 11 Page - Analog Devices |
11 / 20 page Data Sheet AD5543/AD5553 Rev. F | Page 11 of 20 APPLICATIONS INFORMATION STABILITY VDD VREF VREF VDD U2 U1 AD5543/AD5553 VO GND IOUT RFB AD8628 C1 Figure 21. Optional Compensation Capacitor for Gain Peaking Prevention In the I-to-V configuration, the IOUT of the DAC and the inverting node of the op amp must be connected as close as possible to each other, and proper PCB layout technique must be employed. Because every code change corresponds to a step function, gain peaking may occur if the op amp has limited GBP and there is excessive parasitic capacitance at the inverting node. An optional compensation capacitor, C1, can be added for stability, as shown in Figure 21. C1 should be found empirically, but 20 pF is generally adequate for the compensation. POSITIVE VOLTAGE OUTPUT To achieve the positive voltage output, an applied negative reference to the input of the DAC is preferred over the output inversion through an inverting amplifier because of the tolerance errors of the resistors. To generate a negative reference, the reference can be level-shifted by an op amp such that the VOUT and GND pins of the reference become the virtual ground and −2.5 V, respectively (see Figure 22). VREF VDD U2 U1 AD5543/AD5553 VO GND IOUT RFB 1/2AD8628 1/2AD8620 VOUT VIN GND V+ V– +5V –5V ADR03 +5V –2.5V U3 U4 C1 0V < VO < +2.5V Figure 22. Positive Voltage Output Configuration BIPOLAR OUTPUT The AD5543/AD5553 are inherently 2-quadrant multiplying DACs. That is, they can easily be set up for unipolar output operation. The full-scale output polarity is the inverse of the reference input voltage. In some applications, it may be necessary to generate the full 4-quadrant multiplying capability or a bipolar output swing, which is easily accomplished by using an additional U4 external amplifier configured as a summing amplifier (see Figure 23). In this circuit, the second amplifier, U4, provides a gain of 2 that increases the output span magnitude to 5 V. Biasing the external amplifier with a 2.5 V offset from the reference voltage results in a full 4-quadrant multiplying circuit. The transfer equation of this circuit shows that both negative and positive output voltages are created as the input data (D) is incremented from code zero (VOUT = −2.5 V) to midscale (VOUT = 0 V) to full-scale (VOUT = +2.5 V). VOUT = (D/32,768 − 1) × VREF (AD5543) (3) VOUT = (D/16,384 − 1) × VREF (AD5553) (4) For the AD5543, the resistance tolerance becomes the dominant error of which users should be aware. VREF VDD U2 U1 AD5553 ONLY VO GND IOUT RFB 1/2AD8620 VOUT VIN GND ADR03 U3 1/2AD8620 V+ V– +5V –5V +5V U4 C1 –2.5V < VO < +2.5V C2 R3 R1 10k Ω ± 0.01% 5k Ω ± 0.01% 10kΩ ± 0.01% +5V R2 Figure 23. 4-Quadrant Multiplying Application Circuit |
类似零件编号 - AD5543_12 |
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类似说明 - AD5543_12 |
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