a FEATURES 12-Bit Multiplying DACs Guaranteed Specifications with +3.3 V/+5 V Supply 0.5 LSBs INL and DNL Low Power: 5 mW typ Fast Interface 40 ns Strobe Pulsewidth (AD7943) 40 ns Write Pulsewidth (AD7945, AD7948) Low Glitch: 60 nV-s with Amplifier Connected Fast Settling: 600 ns to 0.01% with AD843 +3.3 V/+5 V Multiplying 12-Bit DACs AD7943/AD7945/AD7948 FUNCTIONAL BLOCK DIAGRAMS VDD RFB AD7943 IOUT1 12-BIT DAC VREF IOUT2 CLR LD1 LD2 DAC REGISTER AGND SRI INPUT SHIFT REGISTER SRO APPLICATIONS Battery-Powered Instrumentation Laptop Computers Upgrades for All 754x Series DACs (5 V Designs) STB1 STB2 STB3 STB4 VDD GENERAL DESCRIPTION The AD7943, AD7945 and AD7948 are fast 12-bit multiplying DACs that operate from a single +5 V supply (Normal Mode) and a single +3.3 V to +5 V supply (Biased Mode). The AD7943 has a serial interface, the AD7945 has a 12-bit parallel interface, and the AD7948 has an 8-bit byte interface. They will replace the industry-standard AD7543, AD7545 and AD7548 in many applications, and they offer superior speed and power consumption performance. The AD7943 is available in 16-lead DIP, 16-lead SOP (Small Outline Package) and 20-lead SSOP (Shrink Small Outline Package). RFB AD7945 The AD7948 is available in 20-lead DIP, 20-lead SOP and 20lead SSOP. IOUT1 12-BIT DAC VREF AGND 12 CS WR INPUT LATCH 12 DB11–DB0 VREF DGND RFB VDD IOUT1 12-BIT DAC 12 The AD7945 is available in 20-lead DIP, 20-lead SOP and 20lead SSOP. DGND AGND AD7948 DF/DOR CTRL DATA OVERRIDE LOGIC 12 LDAC DAC REGISTER 12 INPUT REGISTERS WR CONTROL LOGIC CSLSB 12 CSMSB DATA STEERING LOGIC 8 DB7–DB0 DGND 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 which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781/329-4700 World Wide Web Site: http://www.analog.com Fax: 781/326-8703 © Analog Devices, Inc., 1998 AD7943/AD7945/AD7948–SPECIFICATIONS1 NORMAL MODE (AD7943: VDD = +4.5 V to +5.5 V; VIOUT1 = VIOUT2 = AGND = 0 V; VREF = +10 V; TA = TMIN to TMAX, unless otherwise noted. AD7945, AD7948: VDD = +4.5 V to +5.5 V; VIOUT1 = AGND = 0 V; VREF = +10 V; T A = TMIN to TMAX, unless otherwise noted.) Parameter B Grades2 T Grade2, 3 Units Test Conditions/Comments ACCURACY Resolution Relative Accuracy Differential Nonlinearity 12 ± 0.5 ± 0.5 12 ± 0.5 ± 0.5 Bits LSB max LSB max 1 LSB = VREF/212 = 2.44 mV when VREF = 10 V ±2 2 5 ±2 2 5 LSB max ppm FSR/°C typ ppm FSR/°C max 10 100 10 100 nA max nA max See Terminology Section Typically 20 nA over Temperature 6 12 6 12 kΩ min kΩ max Typical Input Resistance = 9 kΩ DIGITAL INPUTS VINH, Input High Voltage VINL, Input Low Voltage IINH , Input Current CIN, Input Capacitance4 2.4 0.8 ±1 10 2.4 0.8 ±1 10 V min V max µA max pF max DIGITAL OUTPUT (AD7943 SRO) Output Low Voltage (V OL) Output High Voltage (V OH) 0.2 VDD – 0.2 0.2 VDD – 0.2 V max V min 4.5/5.5 4.5/5.5 V min/V max –75 5 –75 5 dB typ µA max 5 5 µA max Gain Error TMIN to TMAX Gain Temperature Coefficient 4 Output Leakage Current IOUT1 @ +25°C TMIN to TMAX REFERENCE INPUT Input Resistance POWER REQUIREMENTS VDD Range Power Supply Sensitivity4 ∆Gain/∆VDD IDD (AD7943) IDD (AD7945, AD7948) All Grades Guaranteed Monotonic over Temperature For 1 CMOS Load VINH = VDD – 0.1 V min, V INL = 0.1 V max. SRO Open Circuit. No STB Signal. Typically 1 µA. Typically 100 µA with a 1 MHz STB Frequency. At Input Levels of 0.8 V and 2.4 V, IDD Is Typically 2.5 mA. VINH = VDD – 0.1 V min, V INL = 0.1 V max. Typically 1 µA. At Input Levels of 0.8 V and 2.4 V, IDD Is Typically 2.5 mA. NOTES 1 The AD7943, AD7945 and AD7948 are specified in the normal current mode configuration and in the biased current mode for single-supply applications. Figures 14 and 15 are examples of normal mode operation. 2 Temperature ranges as follows: B Grades: –40°C to +85°C; T Grade: –55°C to +125°C. 3 The T Grade applies to the AD7945 only. 4 Guaranteed by design. Specifications subject to change without notice. –2– REV. B AD7943/AD7945/AD7948 SPECIFICATIONS1 BIASED MODE (AD7943: VDD = +3 V to +5.5 V; VIOUT1 = VIOUT2 = AGND = 1.23 V; VREF = +0 V to 2.45 V; TA = TMIN to TMAX, unless otherwise noted. AD7945, AD7948: VDD = +3 V to +5.5 V; VIOUT1 = AGND = 1.23 V; VREF = +0 V to 2.45 V; TA = TMIN to TMAX, unless otherwise noted.) Parameter A Grades2 Units Test Conditions/Comments ACCURACY Resolution 12 Bits Relative Accuracy Differential Nonlinearity ±1 ± 0.9 1 LSB = (VIOUT1 – VREF)/212 = 300 µV When VIOUT1 = 1.23 V and VREF = 0 V LSB max LSB max Gain Error @ +25°C TMIN to TMAX Gain Temperature Coefficient3 ±3 ±4 2 5 LSB max LSB max ppm FSR/°C typ ppm FSR/°C max Output Leakage Current IOUT1 @ +25°C TMIN to TMAX Input Resistance @ IOUT2 Pin (AD7943) @ AGND Pin (AD7945, AD7948) See Terminology Section 10 100 nA max nA max 6 6 kΩ min kΩ min DIGITAL INPUTS VINH, Input High Voltage @ VDD = +5 V VINH, Input High Voltage @ VDD = +3.3 V VINL, Input Low Voltage @ VDD = +5 V VINL, Input Low Voltage @ VDD = +3.3 V IINH, Input Current CIN, Input Capacitance3 2.4 2.1 0.8 0.6 ±1 10 V min V min V max V max µA max pF max DIGITAL OUTPUT (SRO) Output Low Voltage (VOL) Output High Voltage (VOH) 0.2 VDD – 0.2 V max V min 3.0/5.5 V min/V max –75 5 dB typ µA max 5 µA max POWER REQUIREMENTS VDD Range Power Supply Sensitivity3 ∆Gain/∆VDD IDD (AD7943) IDD (AD7945, AD7948) All Grades Guaranteed Monotonic over Temperature Typically 20 nA over Temperature This Varies with DAC Input Code For 1 CMOS Load VINH = VDD – 0.1 V min, VINL = 0.1 V max. SRO Open Circuit; No STB Signal; Typically 1 µA. Typically 100 µA with 1 MHz STB Frequency. VINH = VDD – 0.1 V min, VINL = 0.1 V max. Typically 1 µA. NOTES 1 These specifications apply with the devices biased up at 1.23 V for single supply applications. The model numbering reflects this by means of a “–B” suffix (for example: AD7943AN-B). Figure 16 is an example of Biased Mode Operation. 2 Temperature ranges as follows: A Versions: –40°C to +85°C. 3 Guaranteed by design. Specifications subject to change without notice. REV. B –3– AD7943/AD7945/AD7948 AC PERFORMANCE CHARACTERISTICS NORMAL MODE (AD7943: VDD = +4.5 V to +5.5 V; VIOUT1 = VIOUT2 = AGND = 0 V. AD7945, AD7948: VDD = +4.5 V to +5.5 V; VIOUT1 =AGND = 0 V. VREF = 6 V rms, 1 kHz sine wave; TA = TMIN to TMAX; DAC output op amp is AD843; unless otherwise noted.) These characteristics are included for Design Guidance and are not subject to test. Parameter B Grades T Grade Units Test Conditions/Comments DYNAMIC PERFORMANCE Output Voltage Settling Time 600 700 ns typ Digital to Analog Glitch Impulse 60 60 nV-s typ Multiplying Feedthrough Error Output Capacitance –75 60 30 5 –75 60 30 5 dB max pF max pF max nV-s typ Digital Feedthrough (AD7945, AD7948) 5 5 nV-s typ To 0.01% of Full-Scale Range. VREF = +10 V; DAC Latch Alternately Loaded with All 0s and All 1s Measured with VREF = 0 V. DAC Latch Alternately Loaded with All 0s and All 1s DAC Latch Loaded with All 0s All 1s Loaded to DAC All 0s Loaded to DAC Feedthrough to the DAC Output with LD1, LD2 High and Alternate Loading of All 0s and All 1s into the Input Shift Register Feedthrough to the DAC Output with CS High and Alternate Loading of All 0s and All 1s to the DAC Bus Total Harmonic Distortion Output Noise Spectral Density @ 1 kHz –83 –83 dB typ 35 35 nV/√Hz typ All 1s Loaded to DAC. VREF = 0 V. Output Op Amp Is OP07 Digital Feedthrough (AD7943) Specifications subject to change without notice. AC PERFORMANCE CHARACTERISTICS BIASED MODE (AD7943: VDD = +3 V to +5.5 V; VIOUT1 = VIOUT2 = AGND = 1.23 V. AD7945, AD7948: VDD = +3 V to +5.5 V; VIOUT1 = AGND = 1.23 V. VREF = 1 kHz, 2.45 V p-p, sine wave biased at 1.23 V; DAC output op amp is AD820; TA = TMIN to TMAX ; unless otherwise noted.) These characteristics are included for Design Guidance and are not subject to test. Parameter DYNAMIC PERFORMANCE Output Voltage Settling Time A Grades Units 5 µs typ Digital to Analog Glitch Impulse 60 nV-s typ Multiplying Feedthrough Error Output Capacitance Digital Feedthrough –75 60 30 5 dB max pF max pF max nV-s typ Digital Feedthrough (AD7945, AD7948) 5 nV-s typ Total Harmonic Distortion Output Noise Spectral Density @ 1 kHz –83 dB typ 25 nV/√Hz typ Test Conditions/Comments To 0.01% of Full-Scale Range. VREF = 0 V DAC Latch Alternately Loaded with All 0s and All 1s VREF = 1.23 V. DAC Register Alternately Loaded with All 0s and All 1s DAC Latch Loaded with All 0s All 1s Loaded to DAC All 0s Loaded to DAC Feedthrough to the DAC Output with LD1, LD2 High and Alternate Loading of All 0s and All 1s into the Input Shift Register Feedthrough to the DAC Output with CS High and Alternate Loading of All 0s and All 1s to the DAC Bus All 1s Loaded to DAC. VREF = 1.23 V Specifications subject to change without notice. –4– REV. B AD7943/AD7945/AD7948 AD7943 TIMING SPECIFICATIONS1 (T A = TMIN to TMAX, unless otherwise noted) Limit @ VDD = +3 V to +3.6 V Limit @ VDD = +4.5 V to +5.5 V Units Description tSTB tDS tDH tSRI tLD tCLR tASB 60 15 35 55 55 55 0 40 10 25 35 35 35 0 ns min ns min ns min ns min ns min ns min ns min tSV3 60 35 ns max STB Pulsewidth Data Setup Time Data Hold Time SRI Data Pulsewidth Load Pulsewidth CLR Pulsewidth Min Time Between Strobing Input Shift Register and Loading DAC Register STB Clocking Edge to SRO Data Valid Delay Parameter 2 NOTES 1 All input signals are specified with tr = tf = 5 ns (10% to 90% of 5 V) and timed from a voltage level of 1.6 V. tr and tf should not exceed 1 µs on any digital input. 2 STB mark/space ratio range is 60/40 to 40/60. 3 tSV is measured with the load circuit of Figure 2 and defined as the time required for the output to cross 0.8 V or 2.4 V. Specifications subject to change without notice. t STB STB1, STB2, STB4 STB3 tDH t DS t SRI SRI DB11(N) (MSB) DB10(N) DB0(N) t ASB LD1, LD2, CLR SRO t SV DB0(N–1) DB10(N–1) Figure 1. AD7943 Timing Diagram 1.6mA TO OUTPUT PIN IOL +2.1V CL 50pF 200mA IOH Figure 2. Load Circuit for Digital Output Timing Specifications REV. B –5– t LD, t CLR AD7943/AD7945/AD7948 AD7945 TIMING SPECIFICATIONS1 (T = T A MIN to T MAX, unless otherwise noted) Parameter Limit @ VDD = +3 V to +3.6 V Limit @ VDD = +4.5 V to +5.5 V Units Description tDS tDH tCS tCH tWR 35 10 60 0 60 20 10 40 0 40 ns min ns min ns min ns min ns min Data Setup Time Data Hold Time Chip Select Setup Time Chip Select Hold Time Write Pulsewidth NOTES 1 All input signals are specified with tr = tf = 5 ns (10% to 90% of 5 V) and timed from a voltage level of 1.6 V. Specifications subject to change without notice. tCS tCH CS tWR WR tDS DB11–DB0 tDH DATA VALID Figure 3. AD7945 Timing Diagram AD7948 TIMING SPECIFICATIONS1 (T = T A MIN to TMAX, unless otherwise noted) Parameter Limit @ VDD = +3 V to +3.6 V Limit @ VDD = +4.5 V to +5.5 V Units Description tDS tDH tCWS tCWH tLWS tLWH tWR 45 10 0 0 0 0 60 30 10 0 0 0 0 40 ns min ns min ns min ns min ns min ns min ns min Data Setup Time Data Hold Time CSMSB or CSLSB to WR Setup Time CSMSB or CSLSB to WR Hold Time LDAC to WR Setup Time LDAC to WR Hold Time Write Pulsewidth NOTES 1 All input signals are specified with tr = tf = 5 ns (10% to 90% of 5 V) and timed from a voltage level of 1.6 V. Specifications subject to change without notice. tCWH tCWS CSMSB tCWH tCWS CSLSB tLWH tLWS LDAC tWR tWR WR tDH tDS DB7–DB0 tDH tDS DATA VALID DATA VALID Figure 4. AD7948 Timing Diagram –6– REV. B AD7943/AD7945/AD7948 ABSOLUTE MAXIMUM RATINGS 1 SOP Package, Power Dissipation . . . . . . . . . . . . . . . . . 450 mW θJA Thermal Impedance . . . . . . . . . . . . . . . . . . . . . . 75°C/W Lead Temperature, Soldering Vapor Phase (60 sec) . . . . . . . . . . . . . . . . . . . . . . +215°C Infrared (15 sec) . . . . . . . . . . . . . . . . . . . . . . . . . . +220°C SSOP Package, Power Dissipation . . . . . . . . . . . . . . . . 875 mW θJA Thermal Impedance . . . . . . . . . . . . . . . . . . . . . 132°C/W Lead Temperature, Soldering Vapor Phase (60 sec) . . . . . . . . . . . . . . . . . . . . . . +215°C Infrared (15 sec) . . . . . . . . . . . . . . . . . . . . . . . . . . +220°C (TA = +25°C unless otherwise noted) VDD to DGND . . . . . . . . . . . . . . . . . . . . . . . . . .–0.3 V to +6 V IOUT1 to DGND . . . . . . . . . . . . . . . . . . . –0.3 V to VDD + 0.3 V IOUT2 to DGND . . . . . . . . . . . . . . . . . . . –0.3 V to VDD + 0.3 V AGND to DGND . . . . . . . . . . . . . . . . . –0.3 V to VDD + 0.3 V Digital Input Voltage to DGND . . . . . . –0.3 V to VDD + 0.3 V VRFB, VREF to DGND . . . . . . . . . . . . . . . . . . . . . . . . . . ± 15 V Input Current to Any Pin Except Supplies2 . . . . . . . . ± 10 mA Operating Temperature Range Industrial (A, B Versions) . . . . . . . . . . . . . –40°C to +85°C Extended (T Version) . . . . . . . . . . . . . . . –55°C to +125°C Storage Temperature Range . . . . . . . . . . . . –65°C to +150°C Junction Temperature . . . . . . . . . . . . . . . . . . . . . . . . . +150°C DIP Package, Power Dissipation . . . . . . . . . . . . . . . . 670 mW θJA Thermal Impedance . . . . . . . . . . . . . . . . . . . . . 116°C/W Lead Temperature, Soldering, (10 sec) . . . . . . . . . . +260°C NOTES 1 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 listed in the operational sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. 2 Transient currents of up to 100 mA will not cause SCR latch-up. 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 the AD7943/AD7945/AD7948 feature 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. WARNING! ESD SENSITIVE DEVICE ORDERING GUIDE Model Temperature Range Linearity Error (LSBs) Nominal Supply Voltage Package Option1 AD7943BN AD7943BR AD7943BRS AD7943AN-B AD7943ARS-B AD7945BN AD7945BR AD7945BRS AD7945AN-B AD7945ARS-B AD7945TQ AD7948BN AD7948BR AD7948BRS AD7948AN-B AD7948ARS-B –40°C to +85°C –40°C to +85°C –40°C to +85°C –40°C to +85°C –40°C to +85°C –40°C to +85°C –40°C to +85°C –40°C to +85°C –40°C to +85°C –40°C to +85°C –55°C to +125°C –40°C to +85°C –40°C to +85°C –40°C to +85°C –40°C to +85°C –40°C to +85°C ± 0.5 ± 0.5 ± 0.5 ±1 ±1 ± 0.5 ± 0.5 ± 0.5 ±1 ±1 ±1 ± 0.5 ± 0.5 ± 0.5 ±1 ±1 +5 V +5 V +5 V +3.3 V to +5 V +3.3 V to +5 V +5 V +5 V +5 V +3.3 V to +5 V +3.3 V to +5 V +5 V +5 V +5 V +5 V +3.3 V to +5 V +3.3 V to +5 V N-16 R-16 RS-20 N-16 RS-20 N-20 R-20 RS-20 N-20 RS-20 Q-20 N-20 R-20 RS-20 N-20 RS-20 NOTE 1 N = Plastic DIP; R = SOP (Small Outline Package); RS = SSOP (Shrink Small Outline Package); Q = Cerdip. REV. B –7– AD7943/AD7945/AD7948 TERMINOLOGY Relative Accuracy Output Capacitance Relative Accuracy or endpoint linearity is a measure of the maximum deviation from a straight line passing through the endpoints of the DAC transfer function. It is measured after adjusting for zero error and full-scale error and is normally expressed in Least Significant Bits or as a percentage of fullscale reading. Output Voltage Settling Time Differential Nonlinearity Digital to Analog Glitch Impulse This is the capacitance from the IOUT1 pin to AGND. This is the amount of time it takes for the output to settle to a specified level for a full-scale input change. For these devices, it is specified both with the AD843 as the output op amp in the normal current mode and with the AD820 in the biased current mode. Differential nonlinearity is the difference between the measured change and the ideal 1 LSB change between any two adjacent codes. A specified differential nonlinearity of 1 LSB maximum ensures monotonicity. This is the amount of charge injected into the analog output when the inputs change state. It is specified as the area of the glitch in nV-s. It is measured with the reference input connected to AGND and the digital inputs toggled between all 1s and all 0s. As with Settling Time, it is specified with both the AD817 and the AD820. Gain Error Gain Error is a measure of the output error between an ideal DAC and the actual device output. It is measured with all 1s in the DAC after offset error has been adjusted out and is expressed in Least Significant Bits. Gain error is adjustable to zero with an external potentiometer. This is the error due to capacitive feedthrough from the DAC reference input to the DAC IOUT1 terminal, when all 0s are loaded in the DAC. Output Leakage Current Digital Feedthrough AC Feedthrough Error Output leakage current is current which flows in the DAC ladder switches when these are turned off. For the IOUT1 terminal, it can be measured by loading all 0s to the DAC and measuring the IOUT1 current. Minimum current will flow in the IOUT2 line when the DAC is loaded with all 1s. When the device is not selected, high frequency logic activity on the device digital inputs is capacitively coupled through the device to show up as noise on the IOUT1 pin and subsequently on the op amp output. This noise is digital feedthrough. PIN CONFIGURATIONS DIP/SOP SSOP DIP/SOP/SSOP DIP/SOP/SSOP IOUT1 1 16 RFB IOUT1 1 20 RFB IOUT1 1 20 RFB IOUT1 1 20 IOUT2 2 15 VREF IOUT2 2 19 VREF AGND 2 19 VREF AGND 2 19 VREF AGND 3 14 VDD AGND 3 18 VDD DGND 3 18 VDD DGND 3 18 VDD AD7943 TOP VIEW 13 CLR (Not to Scale) 12 DGND LD1 5 STB1 4 AD7943 TOP VIEW 17 CLR (Not to Scale) 16 NC NC 5 AD7945 TOP VIEW 17 WR (Not to Scale) 16 CS DB10 5 STB1 4 DB11 4 AD7948 RFB TOP VIEW 17 WR (Not to Scale) 16 CSLSB 5 DF/DOR CSMSB 4 11 STB4 NC 6 15 NC DB9 6 15 DB0 CTRL 6 15 LDAC 7 10 STB3 LD1 7 14 DGND DB8 7 14 DB1 DB7 (MSB) 7 14 DB0 (LSB) STB2 8 9 LD2 SRO 8 13 STB4 DB7 8 13 DB2 DB6 8 13 DB1 SRI 9 12 STB3 DB6 9 12 DB3 DB5 9 12 DB2 11 LD2 DB5 10 11 DB4 DB4 10 11 DB3 SRO 6 SRI STB2 10 NC = NO CONNECT –8– REV. B AD7943/AD7945/AD7948 AD7943 PIN FUNCTION DESCRIPTIONS Pin Mnemonic Description IOUT1 IOUT2 AGND DAC current output terminal 1. DAC current output terminal 2. This should be connected to the AGND pin. This pin connects to the back gates of the current steering switches. In normal operation, it should be connected to the signal ground of the system. In biased single-supply operation it may be biased to some voltage between 0 V and the 1.23 V. See Figure 11 for more details. This is the Strobe 1 input. Data is clocked into the input shift register on the rising edge of this signal. STB3 must be high. STB2, STB4 must be low. Active low inputs. When both of these are low, the DAC register is updated and the output will change to reflect this. Serial Data Input. Data on this line will be clocked into the input shift register on one of the Strobe inputs, when they are enabled. This is the Strobe 2 input. Data is clocked into the input shift register on the rising edge of this signal. STB3 must be high. STB1, STB4 must be low. This is the Strobe 3 input. Data is clocked into the input shift register on the falling edge of this signal. STB1, STB2, STB4, must be low. This is the Strobe 4 input. Data is clocked into the input shift register on the rising edge of this signal. STB3 must be high. STB1, STB2 must be low. Digital Ground. Asynchronous CLR input. When this input is taken low, all 0s are loaded to the DAC latch. Power supply input. This is nominally +5 V for Normal Mode Operation and +3.3 V to +5 V for Biased Mode Operation. DAC reference input. DAC feedback resistor pin. STB1 LD1, LD2 SRI STB2 STB3 STB4 DGND CLR VDD VREF RFB AD7945 PIN FUNCTION DESCRIPTIONS Pin Mnemonic Description IOUT1 AGND DAC current output terminal 1. This pin connects to the back gates of the current steering switches. The DAC IOUT2 terminal is also connected internally to this point. Digital Ground. Digital Data Inputs. Active Low, Chip Select Input. Active Low, Write Input. Power supply input. This is nominally +5 V for Normal Mode Operation and +3.3 V to +5 V for Biased Mode Operation. DAC reference input. DAC feedback resistor pin. DGND DB11–DB0 CS WR VDD VREF RFB REV. B –9– AD7943/AD7945/AD7948 AD7948 PIN FUNCTION DESCRIPTIONS Pin Mnemonic Description IOUT1 AGND DAC current output terminal 1. Normally terminated at the virtual ground of output amplifier. Analog Ground Pin. This pin connects to the back gates of the current steering switches. The DAC IOUT2 terminal is also connected internally to this point. Digital Ground Pin. DGND CSMSB Chip Select Most Significant Byte. Active Low Input. Used in combination with WR to load external data into the input register or in combination with LDAC and WR to load external data into both input and DAC registers. DF/DOR Data Format/Data Override. When this input is low, data in the DAC register is forced to one of two override codes selected by CTRL. When the override signal is removed, the DAC output returns to reflect the value in the DAC register. With DF/DOR high, CTRL selects either a left or right justified input data format. For normal operation, DF/DOR is held high. See Table I. Table I. Truth Table for DF/DOR CTRL DF/DOR CTRL Function 0 0 1 1 0 1 0 1 DAC Register Contents Overridden by All 0s DAC Register Contents Overridden by All 1s Left-Justified Input Data Selected Right-Justified Input Data Selected CTRL Control Input. See DF/DOR description. DB7–DB0 Digital Data Inputs. LDAC Load DAC input, active low. This signal, in combination with others, is used to load the DAC register from either the input register or the external data bus. CSLSB Chip Select Least Significant (LS) Byte. Active Low Input. Used in combination with WR to load external data into the input register or in combination with WR and LDAC to load external data into both input and DAC registers. Table II. Truth Table for AD7948 Write Operation WR CSMSB CSLSB LDAC Function 0 0 0 0 0 1 1 1 0 0 1 X 0 0 1 1 1 X 1 0 1 0 0 X Load LS Byte to Input Register Load LS Byte to Input Register and DAC Register Load MS Byte to Input Register Load MS Byte to Input Register and DAC Register Load Input Register to DAC Register No Data Transfer WR Write input, active low. This active low signal, in combination with others is used in loading external data into the AD7948 input register and in transferring data from the input register to the DAC register. VDD VREF Power supply input. This is nominally +5 V for Normal Mode Operation and +3.3 V to +5 V for Biased Mode Operation. DAC reference input. RFB DAC feedback resistor pin. –10– REV. B AD7943/AD7945/AD7948 Typical Performance Curves 0.5 0.50 LINEARITY ERROR – LSBS 0.4 DNL – LSBS VDD = +5V VREF = +10V OP AMP = AD843 TA = +258C VDD = +5V TA = +258C OP AMP = AD843 0.3 0.2 0.25 0.00 –0.25 0.1 0 –0.50 2 4 6 VREF – Volts 8 10 Figure 5. Differential Nonlinearity Error vs. VREF (Normal Mode) 3072 2048 INPUT CODE 4095 Figure 7. All Codes Linearity In Normal Mode (V DD = +5 V) 1.0 6 VDD = +5V TA = +258C OP AMP = AD843 0.9 1024 0 VDD = +3.3V TA = +258C OP AMP = AD820 5 0.8 INL, DNL – LSBS INL – LSBS 0.7 0.6 0.5 0.4 0.3 0.2 4 3 2 1 0.1 0 2 4 6 VREF – Volts 8 0 0.2 10 Figure 6. Integral Nonlinearity Error vs. VREF (Normal Mode) REV. B 0.4 0.6 0.8 1.0 |VREF – VBIAS| – Volts 1.2 1.4 Figure 8. Linearity Error vs. VREF (Biased Mode) –11– AD7943/AD7945/AD7948 LINEARITY ERROR – LSBS 1.00 VDD = +3.3V VREF = 0V VBIAS = 1.23V OP AMP = AD820 TA = +258C 0.50 5V 200ns 100 90 VDD = +5V TA = +258C VREF = 0V OP AMP = AD711 0.00 AD711 OUTPUT 10 –0.50 0% 50mV 200ns –1.00 0 2048 INPUT CODE 1024 3072 4095 Figure 9. All Codes Linearity in Biased Mode (VDD = +3.3 V) Figure 11. Digital-to-Analog Glitch Impulse –50 0 VDD = +5V TA = +258C VIN = 6V rms OP AMP = AD711 –55 THD – dBs –60 –20 –65 –30 –70 –40 –75 –50 –80 –60 –85 –70 –90 –80 –95 –100 100 VDD = +5V TA = +258C VIN = 20V p-p OP AMP = AD711 –10 DAC LOADED WITH ALL 1S DAC LOADED WITH ALL 0S –90 1k 10k FREQUERCY – Hz –100 100k 1k Figure 10. Total Harmonic Distortion vs. Frequency 10k 100k FREQUENCY – Hz 1M 10M Figure 12. Multiplying Frequency Response vs. Digital Code –12– REV. B AD7943/AD7945/AD7948 GENERAL DESCRIPTION D/A Section UNIPOLAR BINARY OPERATION (Two-Quadrant Multiplication) The AD7943, AD7945 and AD7948 are 12-bit current-output D/A converters. A simplified circuit diagram is shown in Figure 13. The DAC architecture is segmented. This means that the 2 MSBs of the 12-bit data word are decoded to drive the three switches A, B and C. The remaining 10 bits of the data word drive the switches S0 to S9 in a standard inverting R-2R ladder configuration. Figure 14 shows the standard unipolar binary connection diagram for the AD7943, AD7945 and AD7948. When VIN is an ac signal, the circuit performs two-quadrant multiplication. Resistors R1 and R2 allow the user to adjust the DAC gain error. With a specified gain error of 2 LSBs over temperature, these are not necessary in many applications. Circuit offset is due completely to the output amplifier offset. It can be removed by adjusting the amplifier offset voltage. Alternatively, choosing a low offset amplifier makes this unnecessary. Each of the switches A to C steers 1/4 of the total reference current into either IOUT1 or IOUT2 with the remaining 1/4 of the total current passing through the R-2R section. Switches S9 to S0 steer binarily weighted currents into either IOUT1 or IOUT2. If IOUT1 and IOUT2 are kept at the same potential, a constant current flows in each ladder leg, regardless of digital input code. Thus, the input resistance seen at VREF is always constant. It is equal to R/2. The VREF input may be driven by any reference voltage or current, ac or dc that is within the Absolute Maximum Ratings. A1 should be chosen to suit the application. For example, the OP07 is ideal for very low bandwidth applications (10 kHz or R2 10V RFB VIN VOUT = –D × VREF where D is the fractional representation of the digital word loaded to the DAC. D can be set from 0 to 4095/4096, since it has 12-bit resolution. 2R C 2R B R 2R A 2R S9 AGND VOUT A1: OP07 AD711 AD843 AD845 SIGNAL GROUND NOTES 1. ONLY ONE DAC IS SHOWN FOR CLAIRITY. 2. DIGITAL INPUT CONNECTIONS ARE OMITTED. 3. C1 PHASE COMPENSATION (5 – 15pF) MAY BE REQUIRED WHEN USING HIGH SPEED AMPLIFIER. Figure 14. Unipolar Binary Operation lower) while the AD711 is suitable for medium bandwidth applications (200 kHz or lower). For high bandwidth applications of greater than 200 kHz, the AD843 and AD847 offer very fast settling times. The code table for Figure 14 is shown in Table III. Table III. Unipolar Binary Code R 2R S8 A1 IOUT2 AD7943/45/48 VREF R DAC R1 20V The device provides access to the VREF, RFB, and IOUT1 terminals of the DAC. This makes the device extremely versatile and allows it to be configured in several different operating modes. Examples of these are shown in the following sections. The AD7943 also has a separate IOUT2 pin. In the AD7945 and AD7948 this is internally tied to AGND. When an output amplifier is connected in the standard configuration of Figure 14, the output voltage is given by: C1 IOUT1 VREF 2R 2R S0 R/2 RFB IOUT1 IOUT2 SHOWN FOR ALL 1S ON DAC Figure 13. Simplified D/A Circuit Diagram Digital Input MSB LSB Analog Output (VOUT as Shown in Figure 14) 1111 1111 1111 1000 0000 0001 1000 0000 0000 0111 1111 1111 0000 0000 0001 0000 0000 0000 –VREF (4095/4096) –VREF (2049/4096) –VREF (2048/4096) –VREF (2047/4096) –VREF (1/4096) –VREF (0/4096) = 0 NOTE Nominal LSB size for the circuit of Figure 14 is given by: V REF (1/4096). REV. B –13– AD7943/AD7945/AD7948 BIPOLAR OPERATION (Four-Quadrant Multiplication) SINGLE SUPPLY APPLICATIONS Figure 15 shows the standard connection diagram for bipolar operation of the AD7943, AD7945 and AD7948. The coding is offset binary as shown in Table IV. When VIN is an ac signal, the circuit performs four-quadrant multiplication. Resistors R1 and R2 are for gain error adjustment and are not needed in many applications where the device gain error specifications are adequate. To maintain the gain error specifications, resistors R3, R4 and R5 should be ratio matched to 0.01%. R4 20kV R2 10V RFB VIN R5 20kV C1 IOUT1 VREF DAC R1 20V IOUT2 R3 A1 10kV A2 AD7943/45/48 VOUT AGND SIGNAL GROUND NOTES 1. ONLY ONE DAC IS SHOWN FOR CLAIRITY. 2. DIGITAL INPUT CONNECTIONS ARE OMITTED. 3. C1 PHASE COMPENSATION (5 – 15pF) MAY BE REQUIRED WHEN USING HIGH SPEED AMPLIFIER, A1. Figure 15. Bipolar Operation (Four-Quadrant Multiplication) The “-B” versions of the devices are specified and tested for single supply applications. Figure 16 shows the recommended circuit for operation with a single +5 V to +3.3 V supply. The IOUT2 and AGND terminals are biased to 1.23 V. Thus, with 0 V applied to the VREF terminal, the output will go from 1.23 V (all 0s loaded to the DAC) to 2.46 V (all 1s loaded). With 2.45 V applied to the VREF terminal, the output will go from 1.23 V (all 0s loaded) to 0.01 V (all 1s loaded). It is important when considering INL in a single-supply system to realize that most single-supply amplifiers cannot sink current and maintain zero volts at the output. In Figure 16, with VREF = 2.45 V the required sink current is 200 µA. The minimum output voltage level is 10 mV. Op amps like the OP295 are capable of maintaining this level while sinking 200 µA. Figure 16 shows the IOUT2 and AGND terminals being driven by an amplifier. This is to maintain the bias voltage at 1.23 V as the impedance seen looking into the IOUT2 terminal changes. This impedance is code dependent and varies from infinity (all 0s loaded in the DAC) to about 6 kΩ minimum. The AD589 has a typical output resistance of 0.6 Ω and it can be used to drive the terminals directly. However, this will cause a typical linearity degradation of 0.2 LSBs. If this is unacceptable then the buffer amplifier is necessary. Figure 9 shows the typical linearity performance of the AD7943/AD7945/AD7948 when used as in Figure 16 with VDD set at +3.3 V and VREF = 0 V. Suitable dual amplifiers for use with Figure 15 are the OP270 (low noise, low bandwidth, 15 kHz), the AD712 (medium bandwidth, 200 kHz) or the AD827 (wide bandwidth, 1 MHz). +3.3V VDD Table IV. Bipolar (Offset Binary) Code Table Digital Input MSB LSB Analog Output (VOUT as Shown in Figure 15) 1111 1111 1111 1000 0000 0001 1000 0000 0000 0111 1111 1111 0000 0000 0001 0000 0000 0000 +VREF (2047/2048) +VREF (1/2048) +VREF (0/2048) = 0 –VREF (1/2048) –VREF (2047/2048) –VREF (2048/2048) = –VREF VIN RFB C1 IOUT1 VREF DAC IOUT2 AD7943/45/48 AGND A1 VOUT A1: OP295 AD822 OP283 DGND +5V 5.6kV A1 AD589 SIGNAL GROUND Figure 16. Single Supply System NOTE Nominal LSB size for the circuit of Figure 15 is given by: V REF (1/2048). –14– REV. B AD7943/AD7945/AD7948 MICROPROCESSOR INTERFACING AD7943 to ADSP-2101 Interface AD7945 to MC68000 Interface Figure 19 shows the MC68000 interface to the AD7945. The appropriate data is written into the DAC in one MOVE instruction to the appropriate memory location. Figure 17 shows the AD7943 to ADSP-2101 interface diagram. The DSP is set up for alternate inverted framing with an internally generated SCLK. TFS from the ADSP-2101 drives the STB1 input on the AD7943. The serial word length should be set at 12. This is done by making SLEN = 11 (1011 binary). The SLEN field is Bits 3–0 in the SPORT control register (0x3FF6 for SPORT0 and 0x3FF2 for SPORT1). A1 – A23 MC68000 AS With the 16 MHz version of the ADSP-2101, the maximum output SCLK is 8 MHz. The AD7943 setup and hold time of 10 ns and 25 ns mean that it is compatible with the DSP when running at this speed. ADDRESS DECODE CS AD7945 DTACK WR R/W The OUTPUT FLAG drives both LD1 and LD2 and is brought low to update the DAC register and change the analog output. DB11 – DB0 D15 – D0 +5V AD7943 ADSP-2101 CLR TFS STB1 SCLK STB3 DT SRI OUTPUT FLAG LD1 Figure 19. AD7945 to MC68000 Interface AD7948 to Z80 Interface Figure 20 is the interface between the AD7948 and the 8-bit bus of the Z80 processor. Three write operations are needed to load the DAC. The first two load the MS byte and the LS byte and the third brings the LDAC low to update the output. LD2 STB2 STB4 ADDRESS BUS A0 – A15 Figure 17. AD7943 to ADSP-2101 Interface Z80 AD7943 to DSP56001 Interface Figure 18 shows the interface diagram for the AD7943 to the DSP56001. The DSP56001 is configured for normal mode synchronous operation with gated clock. The serial clock, SCK, is set up as an output from the DSP and the serial word length is set for 12 bits (WL0 = 1, WL1 = 0, in Control Register A). SCK from the DSP56001 is applied to the AD7943 STB3 input. Data from the DSP56000 is valid on the falling edge of SCK and this is the edge which clocks the data into the AD7943 shift register. STB1, STB2 and STB4 are tied low on the AD7943 to permanently enable the STB3 input. +5V AD7943 DSP56001 CLR SCK STB3 STD SRI OUTPUT FLAG LD1 LD2 STB1 STB2 ADDRESS DECODE CSLSB LDAC AD7948 WR WR DB7 – DB0 D7 – D0 DATA BUS Figure 20. AD7948 to Z80 Interface When the 12-bit serial word has been written to the AD7943, the LD1, LD2 inputs are brought low to update the DAC register. STB4 Figure 18. AD7943 to DSP56001 Interface REV. B CSMSB MREQ –15– AD7943/AD7945/AD7948 OUTLINE DIMENSIONS Dimensions shown in inches and (mm). 16-Lead Plastic DIP (N-16) 16-Lead SOP (R-16) 16 9 1 8 PIN 1 0.280 (7.11) 0.240 (6.10) 0.060 (1.52) 0.015 (0.38) 0.210 (5.33) MAX 0.160 (4.06) 0.115 (2.93) 1 8 0.1043 (2.65) 0.0926 (2.35) PIN 1 0.0118 (0.30) 0.0040 (0.10) 0.015 (0.381) 0.008 (0.204) 0.070 (1.77) SEATING 0.045 (1.15) PLANE 8° 0.0500 (1.27) 0.0192 (0.49) SEATING 0.0125 (0.32) 0° 0.0157 (0.40) 0.0138 (0.35) PLANE 0.0091 (0.23) 0.0500 (1.27) BSC 20-Lead Plastic DIP (N-20) 20-Lead Cerdip (Q-20) 0.005 (0.13) MIN 1.060 (26.90) 0.925 (23.50) 20 1 PIN 1 0.060 (1.52) 0.015 (0.38) 0.210 (5.33) MAX 0.130 (3.30) MIN 0.160 (4.06) 0.115 (2.93) 20 11 1 10 0.100 (2.54) BSC 0.070 (1.77) SEATING 0.045 (1.15) PLANE 0.310 (7.87) 0.220 (5.59) 0.325 (8.25) 0.300 (7.62) 0.195 (4.95) 0.115 (2.93) PIN 1 1.060 (26.92) MAX 0.200 (5.08) MAX 0.320 (8.13) 0.290 (7.37) 0.150 (3.81) MIN 0.200 (5.08) 0.125 (3.18) 0.015 (0.381) 0.008 (0.204) 0.023 (0.58) 0.014 (0.36) 20-Lead SOP (R-20) 0.100 (2.54) BSC 0.070 (1.78) SEATING 15° 0.030 (0.76) PLANE 0° 0.015 (0.38) 0.008 (0.20) 20-Lead SSOP (RS-20) 0.295 (7.50) 0.271 (6.90) 1 10 0.1043 (2.65) 0.0926 (2.35) 0.311 (7.9) 0.301 (7.64) 11 0.4193 (10.65) 0.3937 (10.00) 20 0.2992 (7.60) 0.2914 (7.40) 0.5118 (13.00) 0.4961 (12.60) 0.0118 (0.30) 0.0040 (0.10) 0.060 (1.52) 0.015 (0.38) 0.0291 (0.74) x 45° 0.0098 (0.25) 20 11 1 10 0.07 (1.78) 0.066 (1.67) 0.078 (1.98) PIN 1 0.068 (1.73) 8° 0.0500 (1.27) 0.0500 0.0192 (0.49) 0° 0.0157 (0.40) (1.27) 0.0138 (0.35) SEATING 0.0125 (0.32) PLANE BSC 0.0091 (0.23) 0.008 (0.203) 0.002 (0.050) –16– 0.212 (5.38) 0.205 (5.21) 0.022 (0.558) 0.014 (0.356) PIN 1 0.098 (2.49) MAX 11 0.280 (7.11) 10 0.240 (6.10) 0.0291 (0.74) x 45° 0.0098 (0.25) 0.0256 (0.65) BSC 8° SEATING 0.009 (0.229) 0° PLANE 0.005 (0.127) 0.037 (0.94) 0.022 (0.559) REV. B PRINTED IN U.S.A. 0.100 (2.54) BSC 9 0.325 (8.26) 0.300 (7.62) 0.195 (4.95) 0.115 (2.93) 0.130 (3.30) MIN 0.022 (0.558) 0.014 (0.356) 16 0.2992 (7.60) 0.2914 (7.40) 0.4193 (10.65) 0.3937 (10.00) 0.840 (21.34) 0.745 (18.92) C1901b–0–5/98 0.4133 (10.50) 0.3977 (10.00)