DAC基本架构II：二进制DAC - Analog Devices

1 1 DAC Walt Kester DAC II DAC MT-015R/8R/4R/2 RVVREFOUTMSBLSBA dapted from: B. D. Smith, "Coding by Feedback Methods," Proceedings of the I. R. E., Vol. 41, August 1953, pp. , 10/08, WK Page 1 of 10 DAC DAC DAC DAC 1920 ( 1 2 3) DAC DAC 1 DAC DAC DAC DAC DAC 2A( ) 2B( ) N DAC 1:2:4:8:..:2N 1 N LSB 2N 1 MSB 1 IC 8 DAC 128:1 MT-015 DIFFICULT TO FABRICATE IN ICFORM DUE TO LARGE RESISTOR OR CURRENT RATIOS FOR HIGH RESOLUTIONSVREFMSBLSBR2R4R8 RVREFMSBLSBR2R4R8 RCURRENT OUTPUTSINTO VIRTUAL GROUNDS(A) RESISTOR(B) CURRENT SOURCETI/2I/4I/8 LSBMSBIPage 2 of 10 2 DAC MSB DAC ( DAC ) DAC 3 4 DAC 3 DAC DAC DAC ADC ADC ADC 1990 ADC ADC ADC ADC R-2R DAC ADC CMOS ( )

2 DAC ADC ( ADI PulSAR ) 3 ADC DAC 4 4 R-2R MT-015_+_+C/ 4C/ 2CC/ 4 AINVREFSINSCS1S2S3S4 BIT1(MSB)BIT2 BIT3(LSB)SWITCHES SHOWN IN TRACK (SAMPLE) MODEAACTOTAL= 2C2R2R2R2R2 RRRRPage 3 of 10 DAC DAC (SHA) SHA SHA R-2R DAC DAC R-2R 4 2:1 N DAC 2N R-2R DAC 5 R-2R DACMT-0152 RRRR2R2R2R2 RVVREFOUTMSBLSBA dapted from: B. D. Smith, "Coding by Feedback Methods," Proceedings of the I. R. E., Vol. 41, August 1953, pp. 1053-1058 Page 4 of 10 5 R-2R DAC VREF B.

3 D. Smith 1953 ( 3) VREF (VREF ) DAC VREF 6 R-2R DAC DAC VREF ( ) VREF ( ) ( ) (I/V) DAC R-2R DAC 6 R-2R DAC DACMT-0152 RRRR2R2R2R2 RVREFVREFMSBLSBCURRENTOUTPUTINTOVIRTUALG ROUND<< R**GAIN TRIM IF REQUIREDPage 5 of 10 ( CMOS ) DAC (MDAC) ( DAC ) CMOS MDAC 5V 30 V ( 60V ) DAC DAC DAC DAC DAC MDAC MDAC 0 10:1 6:1 DAC DAC MT-015 IIIIOUTPUTMSBRRR2R2R2 RAdapted from: Bernard M.

4 Gordon and Robert P. Talambiras, "Signal Conversion Apparatus,"U. S. Patent 3,108,266, filed July 22, 1955, issued October 22, 19632R2 RLSBPage 6 of 10 DAC ( ) ( ) DAC DAC MDAC CMOS VREF 6 MDAC R-2R DAC R-2R 7 EPSCO( Analogic, Inc.) Bernard M. Gordon 11 50 kSPS ADC Gordon 1955 ( 5) ADC DAC R DAC 2:1 R-2R 8 DAC 1V DAC 7 R-2R 8 9 4 DAC AD550 DAC MT-015R (CAN BE EXTERNAL)OUTPUTII/2I/4I/8 MSBLSBVBCURRENTOUTPUT2RR4R8 RII/2I/4I/8 MSB VEXTERNALTHIN FILMRESISTORNETWORKPage 7 of 10 DAC 1970 ADI AD550 DAC (4 ) IC 9 (8:4:2.)

5 1) VBE 10 R-2R MT-015 VBCURRENTOUTPUT2R2R2R2 RII/2I/4I/8 MSB VRRR2RI/8I/2I/4I/8 IMSB16:1 ATTENUATORI/2I/4I/8II/2I/4I/8I16:1 ATTENUATORLSBCURRENT OUTPUTPage 8 of 10 10 4 DAC R/2R 11 12 DAC 11 AD550 16:1 12 DAC 16:1 (AD550 DAC) (AD850) 1970 12 DAC IC DAC James J. Pastoriza (1970 6) MT-015AD550 " DAC"QUAD SWITCH,QUAD CURRENTSOURCEAD550 " DAC"QUAD SWITCH,QUAD CURRENTSOURCEAD550 " DAC"QUAD SWITCH,QUAD CURRENTSOURCEREFERENCECIRCUIT+ AD850 CURRENT SETTING AND INTERSTAGE ATTENUATORPRECISION THIN FILM RESISTOR NETWORK RiVOUTLOGIC INPUTSJa mes J.

6 Pastoriza, "Solid State Digital-to- Analog Converter," Patent 3,747,088, filed December 30, 1970, issued July 17, 1973OP AMP 12 1970 12 DAC Page 9 of 10 12 1970 12 DAC 12 7 12 DAC 12 DAC 4 DAC 8:4:2:1 15 ADI Paul Brokaw 2:1 Paul Brokaw (1975 ) ( 8) IC DAC Page 10 of 10 MT-015 M. Rainey, "Facsimile Telegraph System," Patent 1,608,527, filed July 20, 1921, issued November 30, 1926.

7 (the first PCM patent. Also shows a relay-based 5-bit electro-mechanical flash converter and a binary DAC using relays and multiple resistors). C. Schelleng, "Code Modulation Communication System," U. S. Patent 2,453,461, Filed June 19, 1946, Issued November 9, 1948. (vacuum tube binary DAC using binary weighted voltages summed into load resistor with equal resistor weights). D. Smith, "Coding by Feedback Methods," Proceedings of the I. R. E., Vol. 41, August 1953, pp. 1053-1058. (Smith uses an internal binary weighted DAC and also points out that a non-linear transfer function can be achieved by using a DAC with non-uniform bit weights, a technique which is widely used in today's vo iceband ADCs with built-in companding.)

8 He was also one of the first to propose using an R/2R ladder network within the DAC core). K. Smith, "Digital Attenuator," U. S. Patent 1,976,527, filed July 17, 1958, issued March 21, 1961. (d escribes a tr ansistorized voltage output DAC sim ilar to B. D. Smith above). M. Gordon and Robert P. Talambiras, "Signal Conversion Apparatus," U. S. Patent 3,108,266, filed Ju ly 22, 1955, issued October 22, 1963. (classic patent describing Gordon's 11-bit, 50kSPS vacuum tube successive approximation ADC done at Epsco. The internal DAC represents the first known use of equal currents switched into an R/2R ladder network.) J. Pastoriza, "Solid State Digital-to- Analog Converter," Patent 3,747,088, filed December 30, 1970, issued July 17, 1973.

9 (the first patent on the quad switch approach to building high resolution DACs). R. Hnatek, A User's Handbook of D/A and A/D Converters, John Wiley, New York, 1976, ISBN 0-471-40109-9, pp. 282-295. (contains an excellent description of the Analog Devices ' AD550 monolithic DAC quad current switch, and AD850 thin film network building blocks for 12-bit DACs introduced in 1970 ). Paul Brokaw, "Digital-to- Analog Converter with Current Source Transistors Operated Accurately at Different Current Densities," Patent 3,940,760, f iled March 21, 1975, issued February 24, 1976. (the most referenced data converter patent ever issued). Kester, Analog -Digital Conversion, Analog Devices , 2004, ISBN 0-916550-27-3, Chapter 3. Also available as The Data Conversion Handbook, Elsevier/Newnes, 2005, ISBN 0-7506-7841-0, Chapter 3.

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