10-Bit, 210 MSPS TxDAC(R) D/A Converter AD9740 FEATURES APPLICATIONS High performance member of pin-compatible TxDAC product family Excellent spurious-free dynamic range performance SNR @ 5 MHz output, 125 MSPS: 65 dB Twos complement or straight binary data format Differential current outputs: 2 mA to 20 mA Power dissipation: 135 mW @ 3.3 V Power-down mode: 15 mW @ 3.3 V On-chip 1.2 V Reference CMOS-compatible digital interface 28-lead SOIC, 28-lead TSSOP, and 32-lead LFCSP packages Edge-triggered latches Wideband communication transmit channel Direct IF Base stations Wireless local loops Digital radio links Direct digital synthesis (DDS) Instrumentation FUNCTIONAL BLOCK DIAGRAM 3.3V RSET 3.3V REFLO 1.2V REF REFIO FS ADJ CURRENT SOURCE ARRAY DVDD DCOM CLOCK AVDD 150pF SEGMENTED SWITCHES CLOCK SLEEP LSB SWITCHES ACOM AD9740 IOUTA IOUTB LATCHES DIGITAL DATA INPUTS (DB9-DB0) MODE 02911-001 0.1F Figure 1. GENERAL DESCRIPTION The AD9740 1 is a 10-bit resolution, wideband, third generation member of the TxDAC series of high performance, low power CMOS digital-to-analog converters (DACs). The TxDAC family, consisting of pin-compatible 8-, 10-, 12-, and 14-bit DACs, is specifically optimized for the transmit signal path of communication systems. All of the devices share the same interface options, small outline package, and pinout, providing an upward or downward component selection path based on performance, resolution, and cost. The AD9740 offers exceptional ac and dc performance while supporting update rates up to 210 MSPS. The AD9740's low power dissipation makes it well suited for portable and low power applications. Its power dissipation can be further reduced to 60 mW with a slight degradation in performance by lowering the full-scale current output. In addition, a power-down mode reduces the standby power dissipation to approximately 15 mW. A segmented current source architecture is combined with a proprietary switching technique to reduce spurious components and enhance dynamic performance. Edge-triggered input latches and a 1.2 V temperature-compensated band gap reference have been integrated to provide a complete monolithic DAC solution. The digital inputs support 3 V CMOS logic families. PRODUCT HIGHLIGHTS 1. 2. 3. 4. 5. 6. 1 The AD9740 is the 10-bit member of the pin-compatible TxDAC family, which offers excellent INL and DNL performance. Data input supports twos complement or straight binary data coding. High speed, single-ended CMOS clock input supports 210 MSPS conversion rate. Low power: Complete CMOS DAC function operates on 135 mW from a 2.7 V to 3.6 V single supply. The DAC fullscale current can be reduced for lower power operation, and a sleep mode is provided for low power idle periods. On-chip voltage reference: The AD9740 includes a 1.2 V temperature-compensated band gap voltage reference. Industry-standard 28-lead SOIC, 28-lead TSSOP, and 32lead LFCSP packages. Protected by U.S. Patent Numbers 5568145, 5689257, and 5703519. Rev. B Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of their respective owners. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781.329.4700 www.analog.com Fax: 781.461.3113 (c) 2005 Analog Devices, Inc. All rights reserved. AD9740 TABLE OF CONTENTS Features .............................................................................................. 1 DAC Transfer Function ............................................................. 14 Applications....................................................................................... 1 Analog Outputs .......................................................................... 14 Functional Block Diagram .............................................................. 1 Digital Inputs .............................................................................. 15 General Description ......................................................................... 1 Clock Input.................................................................................. 15 Product Highlights ........................................................................... 1 DAC Timing................................................................................ 16 Revision History ............................................................................... 3 Power Dissipation....................................................................... 16 Specifications..................................................................................... 4 Applying the AD9740 ................................................................ 17 DC Specifications ......................................................................... 4 Differential Coupling Using a Transformer............................... 17 Dynamic Specifications ............................................................... 5 Differential Coupling Using an Op Amp................................ 18 Digital Specifications ................................................................... 6 Single-Ended, Unbuffered Voltage Output............................. 18 Absolute Maximum Ratings............................................................ 7 Single-Ended, Buffered Voltage Output Configuration........ 18 Thermal Characteristics .............................................................. 7 Power and Grounding Considerations, Power Supply Rejection...................................................................................... 19 ESD Caution.................................................................................. 7 Pin Configurations and Function Descriptions ........................... 8 Terminology ...................................................................................... 9 Typical Performance Characteristics ........................................... 10 Functional Description .................................................................. 13 Evaluation Board ............................................................................ 20 General Description................................................................... 20 Outline Dimensions ....................................................................... 30 Ordering Guide .......................................................................... 31 Reference Operation .................................................................. 13 Reference Control Amplifier .................................................... 14 Rev. B | Page 2 of 32 AD9740 REVISION HISTORY 12/05--Rev. A to Rev. B Updated Format.................................................................. Universal Changes to General Description and Product Highlights...........1 Changes to Table 1 ............................................................................4 Changes to Table 2 ............................................................................5 Changes to Table 5 ............................................................................8 Changes to Figure 6.........................................................................10 Inserted Figure 11; Renumbered Sequentially ............................10 Changes to Figure 12, Figure 13, Figure 14, and Figure 15 .......11 Changes to Functional Description and Reference Operation Sections..........................................................................13 Inserted Figure 23; Renumbered Sequentially ............................13 Changes to DAC Transfer Function Section and Figure 25 ......14 Changes to Digital Inputs Section.................................................15 Changes to Figure 30 and Figure 31 .............................................17 Updated Outline Dimensions........................................................30 Changes to Ordering Guide...........................................................31 5/03--Rev. 0 to Rev. A Added 32-Lead LFCSP Package ....................................... Universal Edits to Features ................................................................................1 Edits to Product Highlights .............................................................1 Edits to DC Specifications ...............................................................2 Edits to Dynamic Specifications .....................................................3 Edits to Digital Specifications..........................................................4 Edits to Absolute Maximum Ratings..............................................5 Edits to Thermal Characteristics ....................................................5 Edits to Ordering Guide...................................................................5 Edits to Pin Configuration...............................................................6 Edits to Pin Function Descriptions ................................................6 Edits to Figure 2 ................................................................................7 Replaced TPCs 1, 4, 7, and 8............................................................8 Edits to Figure 3 ..............................................................................10 Edits to Functional Description Section ......................................10 Edits to Digital Inputs Section.......................................................12 Added Clock Input Section............................................................12 Added Figure 7 ................................................................................12 Edits to DAC Timing Section........................................................12 Edits to Sleep Mode Operation Section .......................................13 Edits to Power Dissipation Section...............................................13 Renumbered Figures 8 to 26..........................................................13 Added Figure 11 ..............................................................................13 Added Figures 27 to 35...................................................................21 Updated Outline Dimensions........................................................26 5/02--Revision 0: Initial Version Rev. B | Page 3 of 32 AD9740 SPECIFICATIONS DC SPECIFICATIONS TMIN to TMAX, AVDD = 3.3 V, DVDD = 3.3 V, CLKVDD = 3.3 V, IOUTFS = 20 mA, unless otherwise noted. Table 1. Parameter RESOLUTION DC ACCURACY 1 Integral Linearity Error (INL) Differential Nonlinearity (DNL) ANALOG OUTPUT Offset Error Gain Error (Without Internal Reference) Gain Error (With Internal Reference) Full-Scale Output Current 2 Output Compliance Range Output Resistance Output Capacitance REFERENCE OUTPUT Reference Voltage Reference Output Current 3 REFERENCE INPUT Input Compliance Range Reference Input Resistance (External Reference) Small Signal Bandwidth TEMPERATURE COEFFICIENTS Offset Drift Gain Drift (Without Internal Reference) Gain Drift (With Internal Reference) Reference Voltage Drift POWER SUPPLY Supply Voltages AVDD DVDD CLKVDD Analog Supply Current (IAVDD) Digital Supply Current (IDVDD) 4 Clock Supply Current (ICLKVDD) Supply Current Sleep Mode (IAVDD) Power Dissipation4 Power Dissipation 5 Power Supply Rejection Ratio--AVDD 6 Power Supply Rejection Ratio--DVDD6 OPERATING RANGE Min 10 Typ Max Unit Bits -0.7 -0.5 0.15 0.12 +0.7 +0.5 LSB LSB +0.02 +2 +2 20 +1.25 % of FSR % of FSR % of FSR mA V k pF 1.26 V nA 1.25 7 0.5 V k MHz 0 50 100 50 ppm of FSR/C ppm of FSR/C ppm of FSR/C ppm/C -0.02 -2 -2 2 -1 0.1 0.1 100 5 1.14 1.20 100 0.1 2.7 2.7 2.7 -1 -0.04 -40 1 3.3 3.3 3.3 33 8 5 5 135 145 3.6 3.6 3.6 36 9 6 6 145 +1 +0.04 +85 Measured at IOUTA, driving a virtual ground. Nominal full-scale current, IOUTFS, is 32 times the IREF current. 3 An external buffer amplifier with input bias current <100 nA should be used to drive any external load. 4 Measured at fCLOCK = 25 MSPS and fOUT = 1 MHz. 5 Measured as unbuffered voltage output with IOUTFS = 20 mA, 50 RLOAD at IOUTA and IOUTB, fCLOCK = 100 MSPS, and fOUT = 40 MHz. 6 5% power supply variation. 2 Rev. B | Page 4 of 32 V V V mA mA mA mA mW mW % of FSR/V % of FSR/V C AD9740 DYNAMIC SPECIFICATIONS TMIN to TMAX, AVDD = 3.3 V, DVDD = 3.3 V, CLKVDD = 3.3 V, IOUTFS = 20 mA, differential transformer coupled output, 50 doubly terminated, unless otherwise noted. Table 2. Parameter DYNAMIC PERFORMANCE Maximum Output Update Rate (fCLOCK) Output Settling Time (tST) (to 0.1%) 1 Output Propagation Delay (tPD) Glitch Impulse Output Rise Time (10% to 90%)1 Output Fall Time (10% to 90%)1 Output Noise (IOUTFS = 20 mA) 2 Output Noise (IOUTFS = 2 mA)2 Noise Spectral Density 3 AC LINEARITY Spurious-Free Dynamic Range to Nyquist fCLOCK = 25 MSPS; fOUT = 1.00 MHz 0 dBFS Output -6 dBFS Output -12 dBFS Output -18 dBFS Output fCLOCK = 65 MSPS; fOUT = 1.00 MHz fCLOCK = 65 MSPS; fOUT = 2.51 MHz fCLOCK = 65 MSPS; fOUT = 10 MHz fCLOCK = 65 MSPS; fOUT = 15 MHz fCLOCK = 65 MSPS; fOUT = 25 MHz fCLOCK = 165 MSPS; fOUT = 21 MHz fCLOCK = 165 MSPS; fOUT = 41 MHz fCLOCK = 210 MSPS; fOUT = 40 MHz fCLOCK = 210 MSPS; fOUT = 69 MHz Spurious-Free Dynamic Range within a Window fCLOCK = 25 MSPS; fOUT = 1.00 MHz; 2 MHz Span fCLOCK = 50 MSPS; fOUT = 5.02 MHz; 2 MHz Span fCLOCK = 65 MSPS; fOUT = 5.03 MHz; 2.5 MHz Span fCLOCK = 125 MSPS; fOUT = 5.04 MHz; 4 MHz Span Total Harmonic Distortion fCLOCK = 25 MSPS; fOUT = 1.00 MHz fCLOCK = 50 MSPS; fOUT = 2.00 MHz fCLOCK = 65 MSPS; fOUT = 2.00 MHz fCLOCK = 125 MSPS; fOUT = 2.00 MHz Signal-to-Noise Ratio fCLOCK = 65 MSPS; fOUT = 5 MHz; IOUTFS = 20 mA fCLOCK = 65 MSPS; fOUT = 5 MHz; IOUTFS = 5 mA fCLOCK = 125 MSPS; fOUT = 5 MHz; IOUTFS = 20 mA fCLOCK = 125 MSPS; fOUT = 5 MHz; IOUTFS = 5 mA fCLOCK = 165 MSPS; fOUT = 5 MHz; IOUTFS = 20 mA fCLOCK = 165 MSPS; fOUT = 5 MHz; IOUTFS = 5 mA fCLOCK = 210 MSPS; fOUT = 5 MHz; IOUTFS = 20 mA fCLOCK = 210 MSPS; fOUT = 5 MHz; IOUTFS = 5 mA Min Typ Max 210 71 11 1 5 2.5 2.5 50 30 -143 MSPS ns ns pV-s ns ns pA/Hz pA/Hz dBm/Hz 79 75 67 61 84 80 78 76 75 70 60 67 63 dBc dBc dBc dBc dBc dBc dBc dBc dBc dBc dBc dBc dBc 90 90 90 dBc dBc dBc dBc 80 -79 -77 -77 -77 68 64 64 62 64 62 63 60 Rev. B | Page 5 of 32 Unit -71 dBc dBc dBc dBc dB dB dB dB dB dB dB dB AD9740 Parameter Multitone Power Ratio (8 Tones at 400 kHz Spacing) fCLOCK = 78 MSPS; fOUT = 15.0 MHz to 18.2 MHz 0 dBFS Output -6 dBFS Output -12 dBFS Output -18 dBFS Output 1 2 3 Min Typ Max 65 66 60 55 Unit dBc dBc dBc dBc Measured single-ended into 50 load. Output noise is measured with a full-scale output set to 20 mA with no conversion activity. It is a measure of the thermal noise only. Noise spectral density is the average noise power normalized to a 1 Hz bandwidth, with the DAC converting and producing an output tone. DIGITAL SPECIFICATIONS TMIN to TMAX, AVDD = 3.3 V, DVDD = 3.3 V, CLKVDD = 3.3 V, IOUTFS = 20 mA, unless otherwise noted. Table 3. Parameter DIGITAL INPUTS 1 Logic 1 Voltage Logic 0 Voltage Logic 1 Current Logic 0 Current Input Capacitance Input Setup Time (tS) Input Hold Time (tH) Latch Pulse Width (tLPW) CLK INPUTS 2 Input Voltage Range Common-Mode Voltage Differential Voltage 2 Typ 2.1 3 0 -10 -10 Max 0.9 +10 +10 5 2.0 1.5 1.5 0 0.75 0.5 1.5 1.5 3 2.25 Includes CLOCK pin on SOIC/TSSOP packages and CLK+ pin on LFCSP package in single-ended clock input mode. Applicable to CLK+ and CLK- inputs when configured for differential or PECL clock input mode. DB0-DB9 tS tH CLOCK tLPW tPD IOUTA OR IOUTB tST 0.1% Figure 2. Timing Diagram Rev. B | Page 6 of 32 0.1% 02911-002 1 Min Unit V V A A pF ns ns ns V V V AD9740 ABSOLUTE MAXIMUM RATINGS Table 4. Parameter AVDD DVDD CLKVDD ACOM ACOM DCOM AVDD AVDD DVDD CLOCK, SLEEP Digital Inputs, MODE IOUTA, IOUTB REFIO, REFLO, FS ADJ CLK+, CLK-, MODE Junction Temperature Storage Temperature Range Lead Temperature (10 sec) THERMAL CHARACTERISTICS 1 With Respect to ACOM DCOM CLKCOM DCOM CLKCOM CLKCOM DVDD CLKVDD CLKVDD DCOM DCOM ACOM ACOM CLKCOM Min -0.3 -0.3 -0.3 -0.3 -0.3 -0.3 -3.9 -3.9 -3.9 -0.3 -0.3 -1.0 -0.3 -0.3 Max +3.9 +3.9 +3.9 +0.3 +0.3 +0.3 +3.9 +3.9 +3.9 DVDD + 0.3 DVDD + 0.3 AVDD + 0.3 AVDD + 0.3 CLKVDD + 0.3 150 Unit V V V V V V V V V V V V V V C -65 +150 C 300 C Thermal Resistance 28-Lead 300-Mil SOIC JA = 55.9C/W 28-Lead TSSOP JA = 67.7C/W 32-Lead LFCSP JA = 32.5C/W 1 Thermal impedance measurements were taken on a 4-layer board in still air, in accordance with EIA/JESD51-7. Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; functional operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied. Exposure to absolute maximum ratings for extended periods may effect device reliability. ESD CAUTION ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection. Although this product features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality. Rev. B | Page 7 of 32 AD9740 27 DVDD DB7 3 26 DCOM DB6 4 25 MODE DB5 24 AVDD DB3 7 TOP VIEW (Not to Scale) DB2 8 DB3 DB2 DVDD DB1 DB0 NC NC NC 23 RESERVED 22 IOUTA 21 IOUTB DB1 9 20 ACOM DB0 10 19 NC 1 2 3 4 5 6 7 8 PIN 1 INDICATOR AD9740 TOP VIEW (Not to Scale) 24 23 22 21 20 19 18 17 FS ADJ REFIO ACOM IOUTA IOUTB ACOM AVDD AVDD FS ADJ NC 11 18 NC 12 17 REFIO NC 13 16 REFLO NC 14 15 SLEEP NC = NO CONNECT 9 10 11 12 13 14 15 16 AD9740 NC DCOM CLKVDD CLK+ CLK- CLKCOM CMODE MODE DB4 6 02911-003 5 32 31 30 29 28 27 26 25 28 CLOCK DB8 2 NC = NO CONNECT 02911-004 (MSB) DB9 1 DB4 DB5 DB6 DB7 DB8 DB9 (MSB) DCOM SLEEP PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS Figure 4. 32-Lead LFCSP Pin Configuration Figure 3. 28-Lead SOIC and TSSOP Pin Configuration Table 5. Pin Function Descriptions SOIC/TSSOP Pin No. 1 2 to 9 10 11 to 14, 19 15 LFCSP Pin No. 27 28 to 32, 1, 2, 4 5 6 to 9 25 Mnemonic DB9 (MSB) DB8 to DB1 DB0 (LSB) NC SLEEP 16 N/A REFLO 17 23 REFIO 18 20 21 22 23 24 25 N/A 24 19, 22 20 21 N/A 17, 18 16 15 FS ADJ ACOM IOUTB IOUTA RESERVED AVDD MODE CMODE 26 27 28 N/A N/A N/A N/A 10, 26 3 N/A 12 13 11 14 DCOM DVDD CLOCK CLK+ CLK- CLKVDD CLKCOM Description Most Significant Data Bit (MSB). Data Bits 8 to 1. Least Significant Data Bit (LSB). No Internal Connection. Power-Down Control Input. Active high. Contains active pull-down circuit; it can be left unterminated if not used. Reference Ground when Internal 1.2 V Reference Used. Connect to ACOM for both internal and external reference operation modes. Reference Input/Output. Serves as reference input when using external reference. Serves as 1.2 V reference output when using internal reference. Requires 0.1 F capacitor to ACOM when using internal reference. Full-Scale Current Output Adjust. Analog Common. Complementary DAC Current Output. Full-scale current when all data bits are 0s. DAC Current Output. Full-scale current when all data bits are 1s. Reserved. Do Not Connect to Common or Supply. Analog Supply Voltage (3.3 V). Selects Input Data Format. Connect to DCOM for straight binary, DVDD for twos complement. Clock Mode Selection. Connect to CLKCOM for single-ended clock receiver (drive CLK+ and float CLK-). Connect to CLKVDD for differential receiver. Float for PECL receiver (terminations on-chip). Digital Common. Digital Supply Voltage (3.3 V). Clock Input. Data latched on positive edge of clock. Differential Clock Input. Differential Clock Input. Clock Supply Voltage (3.3 V). Clock Common. Rev. B | Page 8 of 32 AD9740 TERMINOLOGY Linearity Error (Also Called Integral Nonlinearity or INL) Linearity error is defined as the maximum deviation of the actual analog output from the ideal output, determined by a straight line drawn from zero to full scale. Power Supply Rejection The maximum change in the full-scale output as the supplies are varied from nominal to minimum and maximum specified voltages. Differential Nonlinearity (or DNL) Settling Time The time required for the output to reach and remain within a specified error band about its final value, measured from the start of the output transition. DNL is the measure of the variation in analog value, normalized to full scale, associated with a 1 LSB change in digital input code. Monotonicity A DAC is monotonic if the output either increases or remains constant as the digital input increases. Glitch Impulse Asymmetrical switching times in a DAC give rise to undesired output transients that are quantified by a glitch impulse. It is specified as the net area of the glitch in pV-s. Offset Error The deviation of the output current from the ideal of zero is called the offset error. For IOUTA, 0 mA output is expected when the inputs are all 0s. For IOUTB, 0 mA output is expected when all inputs are set to 1s. Spurious-Free Dynamic Range The difference, in dB, between the rms amplitude of the output signal and the peak spurious signal over the specified bandwidth. Gain Error The difference between the actual and ideal output span. The actual span is determined by the output when all inputs are set to 1s minus the output when all inputs are set to 0s. Total Harmonic Distortion (THD) THD is the ratio of the rms sum of the first six harmonic components to the rms value of the measured input signal. It is expressed as a percentage or in decibels (dB). Output Compliance Range The range of allowable voltage at the output of a current output DAC. Operation beyond the maximum compliance limits can cause either output stage saturation or breakdown, resulting in nonlinear performance. Multitone Power Ratio The spurious-free dynamic range containing multiple carrier tones of equal amplitude. It is measured as the difference between the rms amplitude of a carrier tone to the peak spurious signal in the region of a removed tone. T Temperature Drift Temperature drift is specified as the maximum change from the ambient (25C) value to the value at either TMIN or TMAX. For offset and gain drift, the drift is reported in ppm of full-scale range (FSR) per C. For reference drift, the drift is reported in ppm per C. 3.3V REFLO 1.2V REF REFIO PMOS CURRENT SOURCE ARRAY FS ADJ RSET 2k 3.3V DVDD DCOM 50 RETIMED CLOCK OUTPUT* LECROY 9210 PULSE GENERATOR MINI-CIRCUITS T1-1T IOUTA LSB SWITCHES SEGMENTED SWITCHES FOR DB9-DB1 CLOCK DVDD DCOM ACOM AD9740 LATCHES IOUTB ROHDE & SCHWARZ FSEA30 SPECTRUM ANALYZER MODE 50 SLEEP 50 CLOCK OUTPUT DIGITAL DATA TEKTRONIX AWG-2021 WITH OPTION 4 Figure 5. Basic AC Characterization Test Setup (SOIC/TSSOP Packages) Rev. B | Page 9 of 32 *AWG2021 CLOCK RETIMED SO THAT THE DIGITAL DATA TRANSITIONS ON FALLING EDGE OF 50% DUTY CYCLE CLOCK. 02911-005 0.1F AVDD 150pF AD9740 TYPICAL PERFORMANCE CHARACTERISTICS 95 95 90 210MSPS (LFCSP) 125MSPS 90 0dBFS 85 85 165MSPS (LFCSP) 80 75 SFDR (dBc) 65MSPS 70 125MSPS (LFCSP) 65 60 -6dBFS 70 65 -12dBFS 60 210MSPS 55 55 165MSPS 50 10 100 fOUT (MHz) 45 0 10 95 90 90 85 85 SFDR (dBc) 75 -6dBFS 70 -12dBFS 55 50 50 15 20 25 5mA 65 55 fOUT (MHz) 10mA 70 60 10 45 0 10 15 20 25 80 Figure 10. SFDR vs. fOUT and IOUTFS @ 65 MSPS and 0 dBFS 95 95 90 90 0dBFS 0dBFS (LFCSP) 85 80 80 75 SFDR (dBc) 85 -6dBFS 70 -12dBFS 65 0dBFS 65 55 55 50 50 5 10 15 20 25 fOUT (MHz) 30 35 40 45 -6dBFS (LFCSP) 70 60 0 -12dBFS (LFCSP) 75 60 02911-008 SFDR (dBc) 5 fOUT (MHz) Figure 7. SFDR vs. fOUT @ 65 MSPS 45 60 20mA 75 60 5 50 80 0dBFS 02911-007 SFDR (dBc) 80 0 40 Figure 9. SFDR vs. fOUT @ 165 MSPS 95 45 30 fOUT (MHz) Figure 6. SFDR vs. fOUT @ 0 dBFS 65 20 02911-010 0 02911-009 50 02911-006 45 75 02911-054 SFDR (dBc) 80 45 -12dBFS 0 10 20 30 -6dBFS 40 50 60 fOUT (MHz) Figure 11. SFDR vs. fOUT @ 210 MSPS Figure 8. SFDR vs. fOUT @ 125 MSPS Rev. B | Page 10 of 32 70 AD9740 95 95 90 125MSPS 125MSPS 85 65MSPS 165MSPS 80 65MSPS 75 SFDR (dBc) SFDR (dBc) 85 165MSPS 210MSPS (LFCSP) 70 210MSPS 65 75 210MSPS (29, 31) 210MSPS (29, 31) LFCSP 65 78MSPS 60 55 55 -20 -15 -10 AOUT (dBFS) -5 0 45 -25 02911-011 45 -25 Figure 12. Single-Tone SFDR vs. AOUT @ fOUT = fCLOCK/11 -20 -15 -10 AOUT (dBFS) -5 02911-014 50 0 Figure 15. Dual-Tone IMD vs. AOUT @ fOUT = fCLOCK/7 95 0.25 90 85 210MSPS (LFCSP) 75 ERROR (LSB) SFDR (dBc) 80 0.15 65MSPS 125MSPS 70 65 0.05 -0.05 165MSPS 60 -0.15 210MSPS 55 -15 -10 AOUT (dBFS) -5 0 -0.25 0 256 Figure 13. Single-Tone SFDR vs. AOUT @ fOUT = fCLOCK/5 512 CODE 768 1024 02911-015 -20 02911-012 45 -25 768 1024 02911-016 50 Figure 16. Typical INL 90 0.25 85 0.15 80 20mA (LFCSP) 70 65 5mA 10mA (LFCSP) 60 0.05 -0.05 -0.15 10mA 5mA (LFCSP) 55 50 0 30 60 90 120 fCLOCK (MSPS) 150 180 210 02911-013 SNR (dB) ERROR (LSB) 20mA 75 -0.25 0 256 512 CODE Figure 17. Typical DNL Figure 14. SNR vs. fCLOCK and IOUTFS @ fOUT = 5 MHz and 0 dBFS Rev. B | Page 11 of 32 AD9740 90 0 fCLOCK = 78MSPS fOUT1 = 15.0MHz fOUT2 = 15.4MHz -10 85 -20 SFDR = 77dBc AMPLITUDE = 0dBFS 80 MAGNITUDE (dBm) SFDR (dBc) 4MHz 75 70 19MHz 65 -30 34MHz -40 -50 -60 -70 60 -80 49MHz 55 0 20 40 TEMPERATURE (C) 60 80 -100 1 6 Figure 18. SFDR vs. Temperature @ 165 MSPS, 0 dBFS 26 31 36 36 0 fCLOCK = 78MSPS fOUT = 15.0MHz -10 -20 -30 MAGNITUDE (dBm) -30 -40 -50 -60 -70 -50 -60 -70 -80 -90 -90 11 16 21 FREQUENCY (MHz) 26 31 36 -100 02911-018 6 SFDR = 72dBc AMPLITUDE = 0dBFS -40 -80 1 fCLOCK = 78MSPS fOUT1 = 15.0MHz fOUT2 = 15.4MHz fOUT3 = 15.8MHz fOUT4 = 16.2MHz -10 SFDR = 77dBc AMPLITUDE = 0dBFS -20 1 6 Figure 19. Single-Tone SFDR 11 16 21 FREQUENCY (MHz) 26 31 Figure 21. Four-Tone SFDR 3.3V REFLO AVDD 150pF 1.2V REF VREFIO REFIO IREF 0.1F RSET 2k 3.3V FS ADJ AD9740 PMOS CURRENT SOURCE ARRAY DVDD DCOM CLOCK ACOM CLOCK SEGMENTED SWITCHES FOR DB9-DB1 LSB SWITCHES VDIFF = VOUTA - VOUTB IOUTA IOUTB LATCHES SLEEP DIGITAL DATA INPUTS (DB9-DB0) Figure 22. Simplified Block Diagram (SOIC/TSSOP Packages) Rev. B | Page 12 of 32 IOUTA IOUTB MODE VOUTA VOUTB RLOAD 50 RLOAD 50 02911-021 MAGNITUDE (dBm) 16 21 FREQUENCY (MHz) Figure 20. Dual-Tone SFDR 0 -100 11 02911-019 -20 02911-017 50 -40 02911-020 -90 AD9740 FUNCTIONAL DESCRIPTION The analog and digital sections of the AD9740 have separate power supply inputs (that is, AVDD and DVDD) that can operate independently over a 2.7 V to 3.6 V range. The digital section, which is capable of operating at a clock rate of up to 210 MSPS, consists of edge-triggered latches and segment decoding logic circuitry. The analog section includes the PMOS current sources, the associated differential switches, a 1.2 V band gap voltage reference, and a reference control amplifier. The DAC full-scale output current is regulated by the reference control amplifier and can be set from 2 mA to 20 mA via an external resistor, RSET, connected to the full-scale adjust (FS ADJ) pin. The external resistor, in combination with both the reference control amplifier and voltage reference, VREFIO, sets the reference current, IREF, which is replicated to the segmented current sources with the proper scaling factor. The full-scale current, IOUTFS, is 32 times IREF. The AD9740 contains an internal 1.2 V band gap reference. The internal reference cannot be disabled, but can be easily overridden by an external reference with no effect on performance. Figure 23 shows an equivalent circuit of the band gap reference. REFIO serves as either an output or an input depending on whether the internal or an external reference is used. To use the internal reference, simply decouple the REFIO pin to ACOM with a 0.1 F capacitor and connect REFLO to ACOM via a resistance less than 5 . The internal reference voltage is present at REFIO. If the voltage at REFIO is to be used anywhere else in the circuit, then an external buffer amplifier with an input bias current of less than 100 nA should be used. An example of the use of the internal reference is shown in Figure 24. AVDD 84A REFIO 7k REFLO Figure 23. Equivalent Circuit of Internal Reference 3.3V OPTIONAL EXTERNAL REF BUFFER REFLO 150pF AVDD 1.2V REF REFIO ADDITIONAL LOAD 0.1F 2k FS ADJ CURRENT SOURCE ARRAY AD9740 Figure 24. Internal Reference Configuration An external reference can be applied to REFIO, as shown in Figure 25. The external reference can provide either a fixed reference voltage to enhance accuracy and drift performance or a varying reference voltage for gain control. Note that the 0.1 F compensation capacitor is not required because the internal reference is overridden, and the relatively high input impedance of REFIO minimizes any loading of the external reference. Rev. B | Page 13 of 32 02911-022 All of these current sources are switched to one or the other of the two output nodes (that is, IOUTA or IOUTB) via PMOS differential current switches. The switches are based on the architecture that was pioneered in the AD9764 family, with further refinements to reduce distortion contributed by the switching transient. This switch architecture also reduces various timing errors and provides matching complementary drive signals to the inputs of the differential current switches. REFERENCE OPERATION 02911-057 Figure 22 shows a simplified block diagram of the AD9740. The AD9740 consists of a DAC, digital control logic, and full-scale output current control. The DAC contains a PMOS current source array capable of providing up to 20 mA of full-scale current (IOUTFS). The array is divided into 31 equal currents that make up the five most significant bits (MSBs). The next four bits, or middle bits, consist of 15 equal current sources whose value is 1/16 of an MSB current source. The remaining LSBs are binary weighted fractions of the middle bits current sources. Implementing the middle and lower bits with current sources, instead of an R-2R ladder, enhances its dynamic performance for multitone or low amplitude signals and helps maintain the DAC's high output impedance (that is, >100 k). AD9740 3.3V REFLO 150pF The two current outputs typically drive a resistive load directly or via a transformer. If dc coupling is required, then IOUTA and IOUTB should be directly connected to matching resistive loads, RLOAD, that are tied to analog common, ACOM. Note that RLOAD can represent the equivalent load resistance seen by IOUTA or IOUTB, as would be the case in a doubly terminated 50 or 75 cable. The single-ended voltage output appearing at the IOUTA and IOUTB nodes is simply AVDD 1.2V REF REFIO AD9740 REFERENCE CONTROL AMPLIFIER 02911-023 CURRENT SOURCE ARRAY FS ADJ Figure 25. External Reference Configuration REFERENCE CONTROL AMPLIFIER The AD9740 contains a control amplifier that is used to regulate the full-scale output current, IOUTFS. The control amplifier is configured as a V-I converter, as shown in Figure 24, so that its current output, IREF, is determined by the ratio of the VREFIO and an external resistor, RSET, as stated in Equation 4. IREF is copied to the segmented current sources with the proper scale factor to set IOUTFS, as stated in Equation 3. The control amplifier allows a wide (10:1) adjustment span of IOUTFS over a 2 mA to 20 mA range by setting IREF between 62.5 A and 625 A. The wide adjustment span of IOUTFS provides several benefits. The first relates directly to the power dissipation of the AD9740, which is proportional to IOUTFS (see the Power Dissipation section). The second relates to a 20 dB adjustment, which is useful for system gain control purposes. The small signal bandwidth of the reference control amplifier is approximately 500 kHz and can be used for low frequency small signal multiplying applications. DAC TRANSFER FUNCTION The AD9740 provides complementary current outputs, IOUTA and IOUTB. IOUTA provides a near full-scale current output, IOUTFS, when all bits are high (that is, DAC CODE = 1023), while IOUTB, the complementary output, provides no current. The current output appearing at IOUTA and IOUTB is a function of both the input code and IOUTFS and can be expressed as: IOUTA = (DAC CODE/1023) x IOUTFS (1) IOUTB = (1023 - DAC CODE)/1024 x IOUTFS (2) where DAC CODE = 0 to 1023 (that is, decimal representation). As mentioned previously, IOUTFS is a function of the reference current IREF, which is nominally set by a reference voltage, VREFIO, and external resistor, RSET. It can be expressed as: IOUTFS = 32 x IREF (3) where IREF = VREFIO/RSET (4) VOUTA = IOUTA x RLOAD (5) VOUTB = IOUTB x RLOAD (6) Note that the full-scale value of VOUTA and VOUTB should not exceed the specified output compliance range to maintain specified distortion and linearity performance. VDIFF = (IOUTA - IOUTB) x RLOAD (7) Substituting the values of IOUTA, IOUTB, IREF, and VDIFF can be expressed as: VDIFF = {(2 x DAC CODE - 1023)/1024} (32 x RLOAD/RSET) x VREFIO (8) Equation 7 and Equation 8 highlight some of the advantages of operating the AD9740 differentially. First, the differential operation helps cancel common-mode error sources associated with IOUTA and IOUTB, such as noise, distortion, and dc offsets. Second, the differential code-dependent current and subsequent voltage, VDIFF, is twice the value of the single-ended voltage output (that is, VOUTA or VOUTB), thus providing twice the signal power to the load. Note that the gain drift temperature performance for a singleended (VOUTA and VOUTB) or differential output (VDIFF) of the AD9740 can be enhanced by selecting temperature tracking resistors for RLOAD and RSET due to their ratiometric relationship, as shown in Equation 8. B ANALOG OUTPUTS The complementary current outputs in each DAC, IOUTA, and IOUTB can be configured for single-ended or differential operation. IOUTA and IOUTB can be converted into complementary single-ended voltage outputs, VOUTA and VOUTB, via a load resistor, RLOAD, as described in the DAC Transfer Function section by Equation 5 through Equation 8. The differential voltage, VDIFF, existing between VOUTA and VOUTB, can also be converted to a single-ended voltage via a transformer or differential amplifier configuration. The ac performance of the AD9740 is optimum and specified using a differential transformer-coupled output in which the voltage swing at IOUTA and IOUTB is limited to 0.5 V. The distortion and noise performance of the AD9740 can be enhanced when it is configured for differential operation. The common-mode error sources of both IOUTA and IOUTB can be significantly reduced by the common-mode rejection of a Rev. B | Page 14 of 32 AD9740 DVDD transformer or differential amplifier. These common-mode error sources include even-order distortion products and noise. The enhancement in distortion performance becomes more significant as the frequency content of the reconstructed waveform increases and/or its amplitude decreases. This is due to the first-order cancellation of various dynamic commonmode distortion mechanisms, digital feedthrough, and noise. Performing a differential-to-single-ended conversion via a transformer also provides the ability to deliver twice the reconstructed signal power to the load (assuming no source termination). Because the output currents of IOUTA and IOUTB are complementary, they become additive when processed differentially. A properly selected transformer allows the AD9740 to provide the required power and voltage levels to different loads. The output impedance of IOUTA and IOUTB is determined by the equivalent parallel combination of the PMOS switches associated with the current sources and is typically 100 k in parallel with 5 pF. It is also slightly dependent on the output voltage (that is, VOUTA and VOUTB) due to the nature of a PMOS device. As a result, maintaining IOUTA and/or IOUTB at a virtual ground via an I-V op amp configuration results in the optimum dc linearity. Note that the INL/DNL specifications for the AD9740 are measured with IOUTA maintained at a virtual ground via an op amp. IOUTA and IOUTB also have a negative and positive voltage compliance range that must be adhered to in order to achieve optimum performance. The negative output compliance range of -1 V is set by the breakdown limits of the CMOS process. Operation beyond this maximum limit can result in a breakdown of the output stage and affect the reliability of the AD9740. The positive output compliance range is slightly dependent on the full-scale output current, IOUTFS. It degrades slightly from its nominal 1.2 V for an IOUTFS = 20 mA to 1 V for an IOUTFS = 2 mA. The optimum distortion performance for a single-ended or differential output is achieved when the maximum full-scale signal at IOUTA and IOUTB does not exceed 0.5 V. DIGITAL INPUTS The AD9740 digital section consists of 10 input bit channels and a clock input. The 10-bit parallel data inputs follow standard positive binary coding, where DB9 is the most significant bit (MSB) and DB0 is the least significant bit (LSB). IOUTA produces a full-scale output current when all data bits are at Logic 1. IOUTB produces a complementary output with the full-scale current split between the two outputs as a function of the input code. 02911-024 DIGITAL INPUT Figure 26. Equivalent Digital Input The digital interface is implemented using an edge-triggered master/slave latch. The DAC output updates on the rising edge of the clock and is designed to support a clock rate as high as 210 MSPS. The clock can be operated at any duty cycle that meets the specified latch pulse width. The setup and hold times can also be varied within the clock cycle as long as the specified minimum times are met, although the location of these transition edges can affect digital feedthrough and distortion performance. Best performance is typically achieved when the input data transitions on the falling edge of a 50% duty cycle clock. CLOCK INPUT SOIC/TSSOP Packages The 28-lead package options have a single-ended clock input (CLOCK) that must be driven to rail-to-rail CMOS levels. The quality of the DAC output is directly related to the clock quality, and jitter is a key concern. Any noise or jitter in the clock translates directly into the DAC output. Optimal performance is achieved if the CLOCK input has a sharp rising edge, because the DAC latches are positive edge triggered. LFCSP Package A configurable clock input is available in the LFCSP package, which allows for one single-ended and two differential modes. The mode selection is controlled by the CMODE input, as summarized in Table 6. Connecting CMODE to CLKCOM selects the single-ended clock input. In this mode, the CLK+ input is driven with rail-to-rail swings and the CLK- input is left floating. If CMODE is connected to CLKVDD, then the differential receiver mode is selected. In this mode, both inputs are high impedance. The final mode is selected by floating CMODE. This mode is also differential, but internal terminations for positive emitter-coupled logic (PECL) are activated. There is no significant performance difference between any of the three clock input modes. Table 6. Clock Mode Selection CMODE Pin CLKCOM CLKVDD Float Clock Input Mode Single-ended Differential PECL The single-ended input mode operates in the same way as the clock input in the 28-lead packages, as described previously. Rev. B | Page 15 of 32 AD9740 75 70 65 55 50MHz SFDR The final clock mode allows for a reduced external component count when the DAC clock is distributed on the board using PECL logic. The internal termination configuration is shown in Figure 27. These termination resistors are untrimmed and can vary up to 20%. However, matching between the resistors should generally be better than 1%. 50 45 40 0 1 2 Sleep Mode Operation 50 VTT = 1.3V NOM 3 Figure 28. SFDR vs. Clock Placement @ fOUT = 20 MHz and 50 MHz (fCLOCK = 165 MSPS) TO DAC CORE 02911-025 50 -1 ns CLK+ CLK- -2 02911-026 50MHz SFDR 35 -3 AD9740 CLOCK RECEIVER 20MHz SFDR 60 dB In the differential input mode, the clock input functions as a high impedance differential pair. The common-mode level of the CLK+ and CLK- inputs can vary from 0.75 V to 2.25 V, and the differential voltage can be as low as 0.5 V p-p. This mode can be used to drive the clock with a differential sine wave because the high gain bandwidth of the differential inputs converts the sine wave into a single-ended square wave internally. Figure 27. Clock Termination in PECL Mode DAC TIMING Input Clock and Data Timing Relationship Dynamic performance in a DAC is dependent on the relationship between the position of the clock edges and the time at which the input data changes. The AD9740 is rising edge triggered, and so exhibits dynamic performance sensitivity when the data transition is close to this edge. In general, the goal when applying the AD9740 is to make the data transition close to the falling clock edge. This becomes more important as the sample rate increases. Figure 28 shows the relationship of SFDR to clock placement with different sample rates. Note that at the lower sample rates, more tolerance is allowed in clock placement, while at higher rates, more care must be taken. The AD9740 has a power-down function that turns off the output current and reduces the supply current to less than 6 mA over the specified supply range of 2.7 V to 3.6 V and the temperature range. This mode can be activated by applying a Logic Level 1 to the SLEEP pin. The SLEEP pin logic threshold is equal to 0.5 AVDD. This digital input also contains an active pull-down circuit that ensures that the AD9740 remains enabled if this input is left disconnected. The AD9740 takes less than 50 ns to power down and approximately 5 s to power back up. POWER DISSIPATION The power dissipation, PD, of the AD9740 is dependent on several factors that include: * * * * The power supply voltages (AVDD, CLKVDD, and DVDD) The full-scale current output (IOUTFS) The update rate (fCLOCK) The reconstructed digital input waveform The power dissipation is directly proportional to the analog supply current, IAVDD, and the digital supply current, IDVDD. IAVDD is directly proportional to IOUTFS, as shown in Figure 29, and is insensitive to fCLOCK. Conversely, IDVDD is dependent on both the digital input waveform, fCLOCK, and digital supply DVDD. Figure 30 shows IDVDD as a function of full-scale sine wave output ratios (fOUT/fCLOCK) for various update rates with DVDD = 3.3 V. Rev. B | Page 16 of 32 AD9740 35 APPLYING THE AD9740 Output Configurations 30 The following sections illustrate some typical output configurations for the AD9740. Unless otherwise noted, it is assumed that IOUTFS is set to a nominal 20 mA. For applications requiring the optimum dynamic performance, a differential output configuration is suggested. A differential output configuration can consist of either an RF transformer or a differential op amp configuration. The transformer configuration provides the optimum high frequency performance and is recommended for any application that allows ac coupling. The differential op amp configuration is suitable for applications requiring dc coupling, bipolar output, signal gain, and/or level shifting within the bandwidth of the chosen op amp. IAVDD (mA) 25 20 15 0 2 4 6 8 10 12 IOUTFS (mA) 14 16 18 02911-027 10 20 Figure 29. IAVDD vs. IOUTFS 20 A single-ended output is suitable for applications requiring a unipolar voltage output. A positive unipolar output voltage results if IOUTA and/or IOUTB is connected to an appropriately sized load resistor, RLOAD, referred to ACOM. This configuration can be more suitable for a single-supply system requiring a dc-coupled, ground referred output voltage. Alternatively, an amplifier could be configured as an I-V converter, thus converting IOUTA or IOUTB into a negative unipolar voltage. This configuration provides the best dc linearity because IOUTA or IOUTB is maintained at a virtual ground. 18 210MSPS 16 IDVDD (mA) 14 165MSPS 12 10 125MSPS 8 6 65MSPS 4 2 1 An RF transformer can be used to perform a differential-tosingle-ended signal conversion, as shown in Figure 32. A differentially coupled transformer output provides the optimum distortion performance for output signals whose spectral content lies within the transformer's pass band. An RF transformer, such as the Mini-Circuits(R) T1-1T, provides excellent rejection of common-mode distortion (that is, evenorder harmonics) and noise over a wide frequency range. It also provides electrical isolation and the ability to deliver twice the power to the load. Transformers with different impedance ratios can also be used for impedance matching purposes. Note that the transformer provides ac coupling only. Figure 30. IDVDD vs. Ratio @ DVDD = 3.3 V 11 10 9 DIFF 7 6 PECL 5 SE 4 3 2 IOUTA 22 1 0 0 50 100 150 200 fCLOCK (MSPS) 250 02911-056 ICLKVDD (mA) 8 MINI-CIRCUITS T1-1T AD9740 RLOAD IOUTB 21 Figure 31. ICLKVDD vs. fCLOCK and Clock Mode OPTIONAL RDIFF Figure 32. Differential Output Using a Transformer Rev. B | Page 17 of 32 02911-030 0.1 RATIO (fOUT/fCLOCK) 02911-055 DIFFERENTIAL COUPLING USING A TRANSFORMER 0 0.01 AD9740 500 AD9740 An op amp can also be used to perform a differential-to-singleended conversion, as shown in Figure 33. The AD9740 is configured with two equal load resistors, RLOAD, of 25 . The differential voltage developed across IOUTA and IOUTB is converted to a single-ended signal via the differential op amp configuration. An optional capacitor can be installed across IOUTA and IOUTB, forming a real pole in a low-pass filter. The addition of this capacitor also enhances the op amp's distortion performance by preventing the DAC's high slewing output from overloading the op amp's input. 500 25 225 IOUTB 21 25 AVDD 1k SINGLE-ENDED, UNBUFFERED VOLTAGE OUTPUT Figure 35 shows the AD9740 configured to provide a unipolar output range of approximately 0 V to 0.5 V for a doubly terminated 50 cable because the nominal full-scale current, IOUTFS, of 20 mA flows through the equivalent RLOAD of 25 . In this case, RLOAD represents the equivalent load resistance seen by IOUTA or IOUTB. The unused output (IOUTA or IOUTB) can be connected to ACOM directly or via a matching RLOAD. Different values of IOUTFS and RLOAD can be selected as long as the positive compliance range is adhered to. One additional consideration in this mode is the integral nonlinearity (INL), discussed in the Analog Outputs section. For optimum INL performance, the single-ended, buffered voltage output configuration is suggested. AD9740 IOUTFS = 20mA VOUTA = 0V TO 0.5V IOUTA 22 50 AD8047 50 IOUTB 21 25 COPT 25 02911-031 500 25 1k Figure 34. Single-Supply DC Differential Coupled Circuit 225 IOUTA 22 COPT Figure 33. DC Differential Coupling Using an Op Amp The common-mode rejection of this configuration is typically determined by the resistor matching. In this circuit, the differential op amp circuit using the AD8047 is configured to provide some additional signal gain. The op amp must operate off a dual supply because its output is approximately 1 V. A high speed amplifier capable of preserving the differential performance of the AD9740 while meeting other system level objectives (that is, cost or power) should be selected. The op amp's differential gain, gain setting resistor values, and full-scale output swing capabilities should all be considered when optimizing this circuit. The differential circuit shown in Figure 34 provides the necessary level shifting required in a single-supply system. In this case, AVDD, which is the positive analog supply for both the AD9740 and the op amp, is also used to level shift the differential output of the AD9740 to midsupply (that is, AVDD/2). The AD8041 is a suitable op amp for this application. 02911-033 AD9740 AD8041 225 IOUTB 21 B DIFFERENTIAL COUPLING USING AN OP AMP 225 IOUTA 22 02911-032 The center tap on the primary side of the transformer must be connected to ACOM to provide the necessary dc current path for both IOUTA and IOUTB. The complementary voltages appearing at IOUTA and IOUTB (that is, VOUTA and VOUTB) swing symmetrically around ACOM and should be maintained with the specified output compliance range of the AD9740. A differential resistor, RDIFF, can be inserted in applications where the output of the transformer is connected to the load, RLOAD, via a passive reconstruction filter or cable. RDIFF is determined by the transformer's impedance ratio and provides the proper source termination that results in a low VSWR. Note that approximately half the signal power is dissipated across RDIFF. Figure 35. 0 V to 0.5 V Unbuffered Voltage Output SINGLE-ENDED, BUFFERED VOLTAGE OUTPUT CONFIGURATION Figure 36 shows a buffered single-ended output configuration in which the op amp U1 performs an I-V conversion on the AD9740 output current. U1 maintains IOUTA (or IOUTB) at a virtual ground, minimizing the nonlinear output impedance effect on the DAC's INL performance as described in the Analog Outputs section. Although this single-ended configuration typically provides the best dc linearity performance, its ac distortion performance at higher DAC update rates can be limited by U1's slew rate capabilities. U1 provides a negative unipolar output voltage, and its full-scale output voltage is simply the product of RFB and IOUTFS. The full-scale output should be set within U1's voltage output swing capabilities by scaling IOUTFS and/or RFB. An improvement in ac distortion performance can result with a reduced IOUTFS because U1 is required to sink less signal current. Rev. B | Page 18 of 32 AD9740 COPT RFB 200 IOUTFS = 10mA AD9740 IOUTA 22 U1 VOUT = IOUTFS x RFB IOUTB 21 02911-034 200 Figure 36. Unipolar Buffered Voltage Output POWER AND GROUNDING CONSIDERATIONS, POWER SUPPLY REJECTION Many applications seek high speed and high performance under less than ideal operating conditions. In these application circuits, the implementation and construction of the printed circuit board is as important as the circuit design. Proper RF techniques must be used for device selection, placement, and routing as well as power supply bypassing and grounding to ensure optimum performance. Figure 41 to Figure 44 illustrate the recommended printed circuit board ground, power, and signal plane layouts implemented on the AD9740 evaluation board. One factor that can measurably affect system performance is the ability of the DAC output to reject dc variations or ac noise superimposed on the analog or digital dc power distribution. This is referred to as the power supply rejection ratio (PSRR). For dc variations of the power supply, the resulting performance of the DAC directly corresponds to a gain error associated with the DAC's full-scale current, IOUTFS. AC noise on the dc supplies is common in applications where the power distribution is generated by a switching power supply. Typically, switching power supply noise occurs over the spectrum from tens of kilohertz to several megahertz. The PSRR vs. frequency of the AD9740 AVDD supply over this frequency range is shown in Figure 37. 85 As a result, the PSRR measurement in Figure 37 represents a worst-case condition in which the digital inputs remain static and the full-scale output current of 20 mA is directed to the DAC output being measured. The following illustrates the effect of supply noise on the analog supply. Suppose a switching regulator with a switching frequency of 250 kHz produces 10 mV of noise and, for simplicity's sake (ignoring harmonics), all of this noise is concentrated at 250 kHz. To calculate how much of this undesired noise appears as current noise superimposed on the DAC's full-scale current, IOUTFS, users must determine the PSRR in dB using Figure 37 at 250 kHz. To calculate the PSRR for a given RLOAD, such that the units of PSRR are converted from A/V to V/V, adjust the curve in Figure 37 by the scaling factor 20 log (RLOAD). For instance, if RLOAD is 50 , then the PSRR is reduced by 34 dB (that is, PSRR of the DAC at 250 kHz, which is 85 dB in Figure 37, becomes 51 dB VOUT/VIN). Proper grounding and decoupling should be a primary objective in any high speed, high resolution system. The AD9740 features separate analog and digital supplies and ground pins to optimize the management of analog and digital ground currents in a system. In general, AVDD, the analog supply, should be decoupled to ACOM, the analog common, as close to the chip as physically possible. Similarly, DVDD, the digital supply, should be decoupled to DCOM as close to the chip as physically possible. For those applications that require a single 3.3 V supply for both the analog and digital supplies, a clean analog supply can be generated using the circuit shown in Figure 38. The circuit consists of a differential LC filter with separate power supply and return lines. Lower noise can be attained by using low ESR type electrolytic and tantalum capacitors. 80 75 70 65 60 FERRITE BEADS 55 TTL/CMOS LOGIC CIRCUITS 50 45 10F-22F TANT. 0.1F CER. ACOM 0 2 4 6 8 FREQUENCY (MHz) 10 12 3.3V POWER SUPPLY Figure 37. Power Supply Rejection Ratio (PSRR) Figure 38. Differential LC Filter for Single 3.3 V Applications Rev. B | Page 19 of 32 02911-036 40 AVDD 100F ELECT. 02911-035 PSRR (dB) Note that the ratio in Figure 37 is calculated as amps out/volts in. Noise on the analog power supply has the effect of modulating the internal switches, and therefore the output current. The voltage noise on AVDD, therefore, is added in a nonlinear manner to the desired IOUT. Due to the relative different size of these switches, the PSRR is very code dependent. This can produce a mixing effect that can modulate low frequency power supply noise to higher frequencies. Worst-case PSRR for either one of the differential DAC outputs occur when the full-scale current is directed toward that output. AD9740 EVALUATION BOARD GENERAL DESCRIPTION The TxDAC family evaluation boards allow for easy setup and testing of any TxDAC product in the SOIC and LFCSP packages. Careful attention to layout and circuit design, combined with a prototyping area, allows the user to evaluate the AD9740 easily and effectively in any application where high resolution, high speed conversion is required. This board allows the user the flexibility to operate the AD9740 in various configurations. Possible output configurations include transformer coupled, resistor terminated, and single and differential outputs. The digital inputs are designed to be driven from various word generators, with the on-board option to add a resistor network for proper load termination. Provisions are also made to operate the AD9740 with either the internal or external reference or to exercise the power-down feature. JP3 CKEXTX BEAD RED TP2 DVDD TB1 1 C7 0.1F 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 DB13X DB12X DB11X DB10X DB9X DB8X DB7X DB6X DB5X DB4X DB3X DB2X DB1X DB0X BLK TP4 + C4 10F 25V C6 0.1F BLK TP7 RP3 RP3 RP3 RP3 RP3 RP3 RP3 RP3 RP4 RP4 RP4 RP4 RP4 RP4 RP4 8 RP4 CKEXTX RIBBON L2 RP5 OPT 1 2 3 4 5 6 7 8 9 10 DCOM R1 R2 R3 R4 R5 R6 R7 R8 R9 DB13X DB12X DB11X DB10X DB9X DB8X DB7X DB6X DB5X DB4X DB3X DB2X DB1X DB0X RP1 OPT 22 16 22 15 22 14 22 13 22 12 22 11 22 10 22 9 22 16 22 15 22 14 22 13 22 12 22 11 22 10 DB13 DB12 DB11 DB10 DB9 DB8 DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0 22 9 RP6 OPT CKEXT DCOM 1 R1 2 R2 3 R3 4 R4 5 R5 6 R6 7 R7 8 R8 9 R9 10 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 DCOM 1 R1 2 R2 3 R3 4 R4 5 R5 6 R6 7 R7 8 R8 9 R9 10 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 1 DCOM 2 R1 3 R2 4 R3 5 R4 6 R5 7 R6 8 R7 9 R8 10 R9 J1 RP2 OPT BLK TP8 TB1 2 L3 BEAD RED TP5 C9 0.1F BLK TP6 + C5 10F 25V C8 0.1F BLK TP10 BLK TP9 TB1 4 Figure 39. SOIC Evaluation Board--Power Supply and Digital Inputs Rev. B | Page 20 of 32 02911-037 AVDD TB1 3 AD9740 AVDD + C14 10F 16V C16 0.1F CUT UNDER DUT C17 0.1F JP6 DVDD C18 0.1F DVDD C19 0.1F R5 OPT S2 IOUTA CLOCK CKEXT AVDD 1 2 3 4 5 6 7 8 9 10 11 12 13 14 DB13 DB12 DB11 DB10 DB9 DB8 DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0 CLOCK DVDD DCOM MODE AVDD RESERVED IOUTA U1 AD9740 IOUTB ACOM NC FS ADJ REFIO REFLO SLEEP 2 A B 3 1 JP5 INT EXT REF 28 27 26 25 24 23 22 21 20 19 18 17 16 15 CLOCK TP1 WHT JP10 A B 2 3 R11 10k S5 JP4 DB13 DB12 DB11 DB10 DB9 DB8 DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0 1 IX DVDD R4 50 R2 10k DVDD C13 OPT JP8 JP2 IOUT MODE AVDD 3 T1 2 R6 OPT 5 1 REF R1 2k 4 S3 6 T1-1T TP3 WHT C11 0.1F C1 0.1F C2 0.1F C12 OPT JP9 AVDD SLEEP TP11 WHT R10 10k S1 IOUTB R3 10k IY Figure 40. SOIC Evaluation Board--Output Signal Conditioning Rev. B | Page 21 of 32 1 2 A B 3 JP11 02911-038 + C15 10F 16V 02911-039 AD9740 02911-040 Figure 41. SOIC Evaluation Board--Primary Side Figure 42. SOIC Evaluation Board--Secondary Side Rev. B | Page 22 of 32 02911-041 AD9740 02911-042 Figure 43. SOIC Evaluation Board--Ground Plane Figure 44. SOIC Evaluation Board--Power Plane Rev. B | Page 23 of 32 02911-043 AD9740 02911-044 Figure 45. SOIC Evaluation Board Assembly--Primary Side Figure 46. SOIC Evaluation Board Assembly--Secondary Side Rev. B | Page 24 of 32 AD9740 RED TP12 TB1 C3 0.1F TB1 CVDD 1 BLK C2 10F 6.3V TP2 2 C10 0.1F 2 4 1 3 6 5 8 7 DB10X 10 9 DB9X 11 DB8X 13 DB7X 15 DB6X 17 DB5X 19 DB4X 21 DB3X 23 DB2X 25 DB1X 27 DB0X 12 L2 BEAD TB3 16 DVDD 1 C7 0.1F TB3 14 RED TP13 18 20 BLK C6 0.1F C4 10F 6.3V TP4 2 22 24 26 28 RED TP5 L3 BEAD C9 0.1F TB4 32 AVDD 1 BLK 36 C8 0.1F C5 10F 6.3V TP6 34 38 40 2 DB13X DB12X DB11X 29 31 33 35 JP3 CKEXTX 37 39 J1 R3 100 R4 100 R15 100 R16 100 R17 100 R18 100 R19 100 DB13X DB12X DB11X DB10X DB9X DB8X DB7X DB6X DB5X DB4X DB3X DB2X DB1X DB0X CKEXTX R21 100 R24 100 R25 100 R26 100 R27 100 R20 100 1 RP3 22 16 2 RP3 22 15 3 RP3 22 14 4 RP3 22 13 5 RP3 22 12 6 RP3 7 RP3 22 11 22 10 8 RP3 22 9 1 RP4 22 16 2 RP4 22 15 3 RP4 22 14 4 RP4 22 13 5 RP4 22 12 6 RP4 7 RP4 22 11 22 10 8 RP4 22 9 DB13 DB12 DB11 DB10 DB9 DB8 DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0 CKEXT R28 100 02911-045 TB4 30 HEADER STRAIGHT UP MALE NO SHROUD L1 BEAD Figure 47. LFCSP Evaluation Board Schematic--Power Supply and Digital Inputs Rev. B | Page 25 of 32 AD9740 AVDD DVDD CVDD C19 0.1F C17 0.1F C32 0.1F SLEEP TP11 WHT R29 10k DB7 DB6 DVDD DB5 DB4 DB3 DB2 DB1 DB0 CVDD CLK CLKB CMODE 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 DB7 DB6 DVDD DB5 DB4 DB3 DB2 DB1 DB0 DCOM U1 CVDD CLK CLKB CCOM CMODE MODE DB8 DB9 DB10 DB11 DB12 DB13 DCOM1 SLEEP FS ADJ REFIO ACOM IA IB ACOM1 AVDD AVDD1 32 31 30 29 28 27 26 25 DB8 DB9 DB10 DB11 DB12 DB13 R11 50k DNP C13 24 23 22 TP3 TP1 WHT WHT JP8 IOUT 3 21 20 19 18 17 TP7 R30 10k 4 5 2 S3 AGND: 3, 4, 5 6 1 AVDD T1 - 1T C11 0.1F JP9 AD9740LFCSP WHT T1 DNP C12 R10 50 CVDD R1 2k 0.1% JP1 02911-046 MODE Figure 48. LFCSP Evaluation Board Schematic--Output Signal Conditioning CVDD 1 7 U4 C20 10F 16V 2 AGND: 5 CVDD: 8 C35 0.1F CVDD R5 120 3 JP2 CKEXT CLK 4 U4 6 AGND: 5 CVDD: 8 R2 120 C34 0.1F S5 AGND: 3, 4, 5 R6 50 02911-047 CLKB Figure 49. LFCSP Evaluation Board Schematic--Clock Input Rev. B | Page 26 of 32 02911-048 AD9740 02911-049 Figure 50. LFCSP Evaluation Board Layout--Primary Side Figure 51. LFCSP Evaluation Board Layout--Secondary Side Rev. B | Page 27 of 32 02911-050 AD9740 02911-051 Figure 52. LFCSP Evaluation Board Layout--Ground Plane Figure 53. LFCSP Evaluation Board Layout--Power Plane Rev. B | Page 28 of 32 02911-052 AD9740 02911-053 Figure 54. LFCSP Evaluation Board Layout Assembly--Primary Side Figure 55. LFCSP Evaluation Board Layout Assembly--Secondary Side Rev. B | Page 29 of 32 AD9740 OUTLINE DIMENSIONS 9.80 9.70 9.60 28 15 4.50 4.40 4.30 1 6.40 BSC 14 PIN 1 0.65 BSC 0.15 0.05 COPLANARITY 0.10 0.30 0.19 1.20 MAX 0.20 0.09 SEATING PLANE 8 0 0.75 0.60 0.45 COMPLIANT TO JEDEC STANDARDS MO-153-AE Figure 56. 28-Lead Thin Shrink Small Outline Package [TSSOP] (RU-28) Dimensions shown in millimeters 18.10 (0.7126) 17.70 (0.6969) 28 15 7.60 (0.2992) 7.40 (0.2913) 1 14 2.65 (0.1043) 2.35 (0.0925) 10.65 (0.4193) 10.00 (0.3937) 0.75 (0.0295) x 45 0.25 (0.0098) 0.30 (0.0118) 0.10 (0.0039) COPLANARITY 0.10 8 1.27 (0.0500) 0.51 (0.0201) SEATING 0.33 (0.0130) 0 BSC PLANE 0.31 (0.0122) 0.20 (0.0079) 1.27 (0.0500) 0.40 (0.0157) COMPLIANT TO JEDEC STANDARDS MS-013-AE CONTROLLING DIMENSIONS ARE IN MILLIMETERS; INCH DIMENSIONS (IN PARENTHESES) ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FOR REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN. Figure 57. 28-Lead Standard Small Outline Package [SOIC] Wide Body (RW-28) Dimensions shown in millimeters and (inches) Rev. B | Page 30 of 32 AD9740 0.60 MAX 5.00 BSC SQ 0.60 MAX PIN 1 INDICATOR TOP VIEW 0.50 BSC 4.75 BSC SQ 0.50 0.40 0.30 32 1 3.25 3.10 SQ 2.95 EXPOSED PAD (BOTTOM VIEW) 17 16 9 8 0.25 MIN 3.50 REF 0.80 MAX 0.65 TYP 12 MAX 1.00 0.85 0.80 PIN 1 INDICATOR 25 24 0.05 MAX 0.02 NOM SEATING PLANE 0.30 0.23 0.18 0.20 REF COPLANARITY 0.08 COMPLIANT TO JEDEC STANDARDS MO-220-VHHD-2 Figure 58. 32-Lead Lead Frame Chip Scale Package [LFCSP_VQ] 5 mm x 5 mm Body, Very Thin Quad (CP-32-2) Dimensions shown in millimeters ORDERING GUIDE Model AD9740AR AD9740ARRL AD9740ARZ 1 AD9740ARZRL1 AD9740ARU AD9740ARURL7 AD9740ARUZ1 AD9740ARUZRL71 AD9740ACP AD9740ACPRL7 AD9740ACPZ1 AD9740ACPZRL71 AD9740-EB AD9740ACP-PCB 1 Temperature Range -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C Package Description 28-Lead Wide Body SOIC 28-Lead Wide Body SOIC 28-Lead Wide Body SOIC 28-Lead Wide Body SOIC 28-Lead TSSOP 28-Lead TSSOP 28-Lead TSSOP 28-Lead TSSOP 32-Lead LFCSP 32-Lead LFCSP_VQ 32-Lead LFCSP_VQ 32-Lead LFCSP_VQ Evaluation Board (SOIC) Evaluation Board (LFCSP) Z = Pb-free part. Rev. B | Page 31 of 32 Package Option RW-28 RW-28 RW-28 RW-28 RU-28 RU-28 RU-28 RU-28 CP-32-2 CP-32-2 CP-32-2 CP-32-2 AD9740 NOTES (c) 2005 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. C02911-0-12/05(B) Rev. B | Page 32 of 32