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DAC715P 数据表(PDF) 8 Page - Texas Instruments |
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DAC715P 数据表(HTML) 8 Page - Texas Instruments |
8 / 14 page 8 ® DAC715 DAC715 CALIBRATION VALUES 1 LEAST SIGNIFICANT BIT = 152 µV DIGITAL INPUT CODE ANALOG BINARY TWO’S OUTPUT COMPLEMENT, BTC (V) DESCRIPTION 7FFFH 9.999847 Full Scale –1LSB | 4000H 7.5 3/4 Scale | 0001H 5.000152 Half Scale + 1LSB 0000H 5 Half Scale FFFFH 4.999847 Half Scale – 1LSB | C000H 2.5 1/4 Scale | 8000H 0 Zero Gain Adjustment Apply the digital input that gives the maximum positive voltage output. Adjust the gain potentiometer or the gain adjust D/A converter for this positive full scale voltage. INSTALLATION GENERAL CONSIDERATIONS Due to the high-accuracy of the DAC715, system design problems such as grounding and contact resistance become very important. A 16-bit converter with a 10V full-scale range has a 1LSB value of 152 µV. With a load current of 5mA, series wiring and connector resistance of only 60m Ω will cause a voltage drop of 300 µV. To understand what this means in terms of a system layout, the resistivity of a typical 1 ounce copper-clad printed circuit board is 1/2 m Ω per square. For a 5mA load, a 10 milliinch wide printed circuit conductor 60 milliinches long will result in a voltage drop of 150 µV. The analog output of DAC715 has an LSB size of 152 µV (–96dB). The noise floor of the D/A must remain below this level in the frequency range of interest. The DAC715’s noise spectral density (which includes the noise contributed by the internal reference) is shown in the Typical Performance Curves section. Wiring to high-resolution D/A converters should be routed to provide optimum isolation from sources of RFI and EMI. The key to elimination of RF radiation or pickup is small loop area. Signal leads and their return conductors should be kept close together such that they present a small capture cross-section for any external field. Wire-wrap construction is not recommended. POWER SUPPLY AND REFERENCE CONNECTIONS Power supply decoupling capacitors should be added as shown in Figure 4. Best performance occurs using a 1 to 10 µF tantalum capacitor at –V CC. Applications with less critical settling time may be able to use 0.01 µF at –V CC as TABLE I. Digital Input and Analog Output Voltage Calibra- tion Values. well as at +V CC. The capacitors should be located close to the package. The DAC715 has separate ANALOG COMMON and DIGI- TAL COMMON pins. The current through DCOM is mostly switching transients and are up to 1mA peak in amplitude. The current through ACOM is typically 5 µA for all codes. Use separate analog and digital ground planes with a single interconnection point to minimize ground loops. The analog pins are located adjacent to each other to help isolate analog from digital signals. Analog signals should be routed as far as possible from digital signals and should cross them at right angles. A solid analog ground plane around the D/A package, as well as under it in the vicinity of the analog and power supply pins, will isolate the D/A from switching currents. It is recommended that DCOM and ACOM be connected directly to the ground planes under the package. If several DAC715s are used or if DAC715 shares supplies with other components, connecting the ACOM and DCOM lines together once at the power supplies rather than at each chip may give better results. LOAD CONNECTIONS Since the reference point for V OUT and VREF OUT is the ACOM pin, it is important to connect the D/A converter load directly to the ACOM pin. Refer to Figure 5. Lead and contact resistances are represented by R 1 through R 3. As long as the load resistance RL is constant, R1 simply introduces a gain error and can be removed by gain adjust- ment of the D/A or system-wide gain calibration. R 2 is part of R L if the output voltage is sensed at ACOM. In some applications it is impractical to return the load to the ACOM pin of the D/A converter. Sensing the output voltage at the SYSTEM GROUND point is reasonable, because there is no change in DAC715 ACOM current, provided that FIGURE 4. Power Supply Connections. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 28 27 26 25 24 23 22 21 20 19 18 17 16 15 + 0.01µF DCOM ACOM V OUT V REF OUT +V CC –V CC 0.01µF + +12V to +15V –12V to –15V |
类似零件编号 - DAC715P |
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类似说明 - DAC715P |
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