AD668 AD [Analog Devices], AD668 Datasheet
AD668
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AD668 Summary of contents
Page 1
... The AD668 is available in four performance grades. The AD668JQ and KQ are specified for operation from +70 C, the AD668AQ is specified for operation from – +85 C, and the AD668SQ specified for operation from – +125 C. All grades are available in a 24-pin cerdip (0.3" ...
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... BINARY, OFFSET BINARY 0 to 10.24, 5. 1.024, 0.512 –2 +1.2 * 160 200 240 * * 99 100 101 * * 1 –2– = –15 V, unless otherwise noted) EE AD668S Max Min Typ Max Units 12 Bits * +1 LSB +1 LSB +1 LSB +1 LSB % of FSR * * * +0 FSR +0 FSR +0 ...
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... V to –16.5 V Power Dissipation 7 PSRR TEMPERATURE RANGE 2 Rated Specification ( Rated Specification (A) Storage NOTES *Same as AD668J/A. 1 Measured in I mode. Specified at nominal 5 V full-scale reference. OUT 2 Measured in V mode, unless otherwise specified. Specified at nominal 5 V OUT full-scale reference. 3 Total resistance. Refer to Figure 4. ...
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... FS) for any bit combina- tion expressed in multiples of 1 LSB. The AD668 is laser trimmed to 1/4 LSB (0.006% of FS) maximum linearity error at +25 C for the K version and 1/2 LSB for the J and S versions. ...
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... ING THE AD668. Subsequent sections contain more detailed information useful in optimizing DAC performance in high speed, high resolution applications. DAC Transfer Function The AD668 may be used either in a current output mode (DAC output connected to a virtual ground voltage output mode (DAC output connected to a resistive load). REV. A ...
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... CURRENT OUTPUT VS. VOLTAGE-OUTPUT As indicated in the FUNCTIONAL DESCRIPTION, the AD668 output may be taken as either a voltage or a current, depending on external circuit connections. In the current output mode, the DAC output (Pin 20) is tied to a summing junction, and the current flowing from the DAC into this summing junc- tion is sensed ...
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... When using low impedance, high current, high accuracy parts such as the AD668, great care must be taken in the routing of not only sig- nal lines, but ground and supply lines as well. The following ac- counting provides a detailed description of the magnitudes and signal dependencies of the currents associated with each of the part’ ...
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... Bit 1’s current will be 4 times Bit 3’s, but all the currents will be below the value specified. APPLYING THE AD668 The following are some typical circuit configurations for the AD668. As Table II indicates, these represent only a sample of the possible implementations REFIN UNIPOLAR, UNBUFFERED VOLTAGE OUTPUT Figure 7 shows a typical topology for generating an unbuffered voltage output ...
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... DC REFERENCE: THE AD586 DRIVING THE AD668 Figure 11 illustrates one of the more obvious analog input sources: a fixed reference. The AD586 produces a temperature stable 5 V analog output to drive the AD668 in the 5 V input –9– AD668 LOAD DAC out- ...
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... The AD568 has an on-board fixed reference and generates a full-scale output voltage of 1.024 V (just as the AD668 does in its unbuffered voltage output mode). This output voltage can be used to di- rectly drive the AD668 in the 1 V reference input mode. Note that in this case, the lower 410 codes of the AD568 are out-of- bounds ...
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... The dominant consideration in the selection of bypass capacitors for the AD668 is minimization of series resistance and inductance. Many capacitors will begin to look inductive at 20 MHz and above. Ceramic and film type capacitors generally feature lower series inductance than tanta- lum or electrolytic types ...
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... Figure 16. Linearity vs. Reference Level AC PERFORMANCE For the purposes of characterizing the frequency domain perfor- mance of the AD668, all bits are turned on and the DAC is es- sentially treated as a voltage amplifier/attenuator. The tests used to generate these performance curves were done using the cir- cuit shown in Figure 12 ...
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... Digital Settling Time Figure 22 illustrates the typical settling characteristic of the AD668 to a full-scale change in digital inputs with the analog input fixed at 100%. The digital driving circuity is shown in Figure 23. This circuit allows the DAC to be toggled between any two codes, and so provides an excellent means of character- izing both settling and glitch performance ...
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... Figure 26 illustrates that, after hold- ing the reference at 0% (REFIN = REFCOM) for 1 s, the AD668 takes return to 10% of full scale once the refer- ence is returned to 100%. This is the worst case: recovery from a completely “off” condition. ...
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... Data skew can allow the DAC output to move a sub- + stantial amount towards full scale or zero (depending upon the 15V direction of the skew) when only a small transition is desired. D1 Great care was taken in the design and layout of the AD668 to IN4735 + 5V ensure that switching times of the DAC switches are symmetri- R5 ...
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... AD668 Figure 28a. PCB Layout of Foil Side Figure 28b. PCB Layout of Component Side OUTLINE DIMENSIONS Dimensions shown in inches and (mm). 24-Pin Cerdip (Suffix Q) –16– REV. A ...