19-1116; Rev 1; 11/96 Microprocessor-Compatible, 14-Bit DACs ____________________________Features The MX7534/MX7535 are high-performance, CMOS, monolithic, 14-bit digital-to-analog converters (DACs). Wafer-level, laser-trimmed, thin-film resistors and temperature-compensated NMOS switches assure operation over the full operating temperature range with exceptional linear and gain stability. ♦ 14-Bit Monotonic Over Full Temperature Range The MX7534 accepts right-justified data in two bytes from an 8-bit bus, while the MX7535 operates with a 14-bit data bus with separate MS-byte and LS-byte select controls. In addition, all digital inputs are compatible with both TTL and 5V CMOS-logic levels. The MX7534/MX7535 are intended for unipolar operation, but may be operated as bipolar DACs with additional external components. Both devices are protected against CMOS latchup, and neither requires the use of external Schottky protection diodes. ♦ Low Power Consumption The MX7534 is available in 20-pin narrow (0.3") DIP, wide SO, or PLCC packages. The MX7535 is available in 28-pin, 600 mil wide DIP, wide SO, or PLCC packages. ________________________Applications Machine and Motion Control Systems Automatic Test Equipment Digital Audio µP-Controlled Calibration Circuitry Programmable-Gain Amplifiers Digitally Controlled Filters Programmable Power Supplies _________________Pin Configurations ♦ Full 4-Quadrant Multiplication ♦ µP-Compatible, Double-Buffered Inputs ♦ Exceptionally Low Gain Tempco (2.5ppm/°C) ♦ Low Output Leakage (<20nA) Over Temp. ♦ TTL and CMOS Compatible ______________Ordering Information PART TEMP. RANGE PIN-PACKAGE INL (LSBs) MX7534KN MX7534JN MX7534KCWP MX7534JCWP MX7534KP MX7534JP MX7534J/D MX7534BQ MX7534AQ MX7534BD MX7534AD MX7534KEWP MX7534JEWP MX7534TQ MX7534SQ MX7534TD MX7534SD 0°C to +70°C 0°C to +70°C 0°C to +70°C 0°C to +70°C 0°C to +70°C 0°C to +70°C 0°C to +70°C -25°C to +85°C -25°C to +85°C -25°C to +85°C -25°C to +85°C -40°C to +85°C -40°C to +85°C -55°C to +125°C -55°C to +125°C -55°C to +125°C -55°C to +125°C 20 Plastic DIP 20 Plastic DIP 20 SO 20 SO 20 PLCC 20 PLCC Dice* 20 CERDIP 20 CERDIP 20 Ceramic SB 20 Ceramic SB 20 SO 20 SO 20 CERDIP 20 CERDIP 20 Ceramic SB 20 Ceramic SB ±1 ±2 ±1 ±2 ±1 ±2 ±2 ±1 ±2 ±1 ±2 ±1 ±2 ±1 ±2 ±1 ±2 Ordering Information continued at end of data sheet. *Dice are tested at +25°C, DC parameters only. _______________Functional Diagrams TOP VIEW REF 1 20 VSS RFB 2 19 VDD IOUT 3 18 CS AGNDS 4 17 WR AGNDF 5 MX7534 16 A0 DGND 6 15 A1 D7 7 14 D0 8 13 D1 D5 9 12 D2 D4 10 11 D3 D6 DIP/SO/PLCC/Ceramic SB MX7535 at end of data sheet. VDD 19 REF 1 MX7534 2 RFB 3 IOUT 4 AGNDS 5 AGNOF 14-BIT DAC 14 DAC REGISTER 6 MS INPUT REGISTER 8 LS INPUT REGISTER 7–14 D7–D0 CONTROL LOGIC 6 DGND 15 A1 16 A0 18 CS 17 WR 20 VSS Functional diagrams continued at end of data sheet. ________________________________________________________________ Maxim Integrated Products 1 For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800 MX7534/MX7535 _______________General Description MX7534/MX7535 Microprocessor-Compatible, 14-Bit DACs ABSOLUTE MAXIMUM RATINGS VDD to DGND ............................................................-0.3V, +17V VSS to AGND .............................................................-15V, +0.3V REF to AGND (MX7534) ......................................................±25V REFS to AGND (MX7535) ....................................................±25V REFF to AGND (MX7535) ....................................................±25V RFB to AGND.......................................................................±25V Digital Input Voltage to DGND.........................-0.3V, VDD + 0.3V IOUT to DGND .................................................-0.3V, VDD + 0.3V AGND to DGND ...............................................-0.3V, VDD + 0.3V Continuous Power Dissipation (TA = +70°C) 20-Pin Plastic DIP (derate 11.11mW/°C above +70°C)....889mW 28-Pin Plastic DIP (derate 14.29mW/°C above +70°C) ......1.14W 20-Pin SO (derate 10.00mW/°C above +70°C)..............800mW 28-Pin SO (derate 12.50mW/°C above +70°C).....................1W 20-Pin PLCC (derate 10.00mW/°C above +70°C) .........800mW 28-Pin PLCC (derate 10.53mW/°C above +70°C) .........842mW 20-Pin CERDIP (derate 11.11mW/°C above +70°C)......889mW 28-Pin CERDIP (derate 16.67mW/°C above +70°C)........1.33W 20-Pin Ceramic SB (derate 11.76mW/°C above +70°C) .............................941mW 28-Pin Ceramic SB (derate 20.00mW/°C above +70°C) ................................1.6W Operating Temperature Ranges MX753_J/K ............................................................0°C to +70°C MX753_A/B ........................................................-25°C to +85°C MX753_EW_.......................................................-40°C to +85°C MX753_S/T.......................................................-55°C to +125°C Storage Temperature Range .............................-65°C to +150°C Lead Temperature (soldering, 10sec) .............................+300°C Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS (VDD = +11.4V to +15.75V (Note 1), VREF = 10V, VIOUT = VAGNDS = VSS = 0V, TA = TMIN to TMAX, unless otherwise noted.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS DC ACCURACY Resolution 14 Bits MX753_K/B/T ±1 MX753_J/A/S ±2 Differential Nonlinearity Guaranteed Monotonic ±1 ±4 Full-Scale Error Measured with internal RFB, MX753_K/B/T includes effects of leakage MX753_J/A/S current and gain TC Relative Accuracy INL Gain Temperature Coefficient (Note 2) Output Leakage Current IOUT LSB ±0.5 ±2.5 MX753_J/A/S ±0.5 ±5 TA = +25°C All digital inputs at 0V, VSS = 0V TA = TMIN to TMAX LSB ±8 MX753_K/B/T All digital inputs at 0V LSB ppm/°C ±5 MX753_J/K/A/B ±25 MX753_S/T ±150 nA REFERENCE INPUT Reference Voltage Input Resistance (Note 3) RREF 3.5 Input High Voltage VINH 2.4 Input Low Voltage VINL 6 10 kΩ DIGITAL INPUTS Digital inputs at 0V or VDD Input Leakage Current Input Capacitance (Note 2) 2 V 0.8 TA = +25°C ±1 TA = TMIN to TMAX ±10 CIN _______________________________________________________________________________________ 7 V µA pF Microprocessor-Compatible, 14-Bit DACs (VDD = +11.4V to +15.75V (Note 1), VREF = 10V, VIOUT = VAGNDS = VSS = 0V, TA = TMIN to TMAX, unless otherwise noted.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS POWER REQUIREMENTS Positive Supply-Voltage Range VDD For specific performance 11.4 15.75 V Negative Supply-Voltage Range VSS For specific performance -200 -500 mV Positive Supply Current IDD Digital inputs at VINH or VINL Negative Supply Current ISS Digital inputs at 0V or VDD MX7534 3 MX7535 4 500 mA µA Note 1: Specifications are guaranteed for VDD of +11.4V to +15.75V. At VDD = +5V, device is still functional with degraded specifications. Note 2: Guaranteed by design, not tested. Note 3: Resistors have a typical -300ppm/°C tempco. AC PERFORMANCE CHARACTERISTICS (Note 4) (VDD = +11.4V to +15.75V, VREF = 10V, VIOUT = VAGND (VAGNDS for MX7535) = VSS = 0V, output amplifier is AD544*, TA = TMIN to TMAX, unless otherwise noted.) PARAMETER TYP MAX UNITS Output Current Setting Time TA = +25°C, to 0.003% of full-scale range, IOUT load = 100Ω II 13pF, DAC register alternately loaded with all 1s and all 0s 0.8 1.5 µs Digital-to-Analog Glitch Impulse Measured with VREF = 0V, IOUT loads = 100Ω II 13pF, DAC register alternately loaded with all 1s and all 0s 50 Multiplying Feedthrough Error (Note 5) VREF = ±10V, 10kHz sine wave, DAC register loaded with all 0s TA = +25°C 3 TA = TMIN to TMAX 5 Power-Supply Rejection ∆VDD = ±5% TA = +25°C ±0.01 TA = TMIN to TMAX ±0.02 Output Capacitance (IOUT Pin) Output Noise Voltage Density (10Hz–100kHz) SYMBOL COUT CONDITIONS MIN nV-sec mVp-p DAC register loaded with all 1s 260 DAC register loaded with all 0s 130 Measured between RFB and IOUT 15 %/% pF nV/Hz Note 4: These characteristics are included for design guidance only, and are not subject to test. Note 5: Feedthrough can be further reduced by connecting the metal lid on the ceramic package to DGND. * AD544 is an Analog Devices part. _______________________________________________________________________________________ 3 MX7534/MX7535 ELECTRICAL CHARACTERISTICS (continued) MX7534/MX7535 Microprocessor-Compatible, 14-Bit DACs TIMING CHARACTERISTICS (MX7534) (VDD = +11.4V to +15.75V, VREF = 10V, VIOUT = VAGND = VSS = 0V, TA = TMIN to TMAX, unless otherwise noted. See Figure 1a for timing diagram.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Address Valid to Write Setup Time t1 0 ns Address Valid to Write Hold Time t2 0 ns Data Setup Time Data Hold Time t3 t4 TA = +25°C 60 TA = -25°C to +85°C 70 TA = -55°C to +125°C 80 TA = +25°C 20 TA = -25°C to +85°C 20 TA = -55°C to +125°C 30 ns ns Chip-Select to Write-Setup Time t5 0 ns Chip-Select to Write-Hold Time t6 0 ns Write Pulse Width t7 TA = +25°C 170 TA = -25°C to +85°C 200 TA = -55°C to +125°C 240 ns TIMING CHARACTERISTICS (MX7535) (VDD = +11.4V to +15.75V, VREF = 10V, VIOUT = VAGNDS = VSS = 0V, TA = TMIN to TMAX, unless otherwise noted. See Figure 1b for timing diagram.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS CSMSB or CSLSB to WR Setup Time t1 0 ns CSMSB or CSLSB to WR Hold Time t2 0 ns LDAC Pulse Width Write Pulse Width Data-Setup Time Data-Hold Time 4 t3 t4 t5 t6 TA = +25°C 170 TA = -25°C to +85°C 200 TA = -55°C to +125°C 240 TA = +25°C 170 TA = -25°C to +85°C 200 TA = -55°C to +125°C 240 TA = +25°C 140 TA = -25°C to +85°C 160 TA = -55°C to +125°C 180 TA = +25°C 20 TA = -25°C to +85°C 20 TA = -55°C to +125°C 30 _______________________________________________________________________________________ ns ns ns ns Microprocessor-Compatible, 14-Bit DACs PIN NAME FUNCTION __________Pin Description (MX7535) PIN NAME REFS Reference Voltage Sense FUNCTION 1 REF Reference Input to DAC 1 2 RFB Feedback Resistor. Used to close the loop around an external op amp. 2 REFF Reference Voltage Force 3 IOUT Current Output 3 RFB Feedback Resistor. Used to close the loop around an external op amp. 4 IOUT Current Output 4 AGNDS 5 AGNDS Analog Ground Sense. Reference point for external circuitry. This pin should carry minimum current. 6 AGNDF Analog Ground Force. Carries current from internal analog ground connections. AGNDS and AGNDF are tied together internally. Digital Ground 5 AGNDF Analog Ground Sense. Reference point for external circuitry. AGNDS should carry minimum current. Analog Ground Force. Carries current from internal analog ground connections. AGNDS and AGNDF are tied together internally. 6 DGND 7 D7 Data Bit 7 7 DGND 8 D6 Data Bit 6 8 D13 Data Bit 13 (MSB) 9 D5 Data Bit 5 or Data Bit 13 (MSB) 9 D12 Data Bit 12 10 D4 Data Bit 4 or Data Bit 12 10 D11 Data Bit 11 11 D3 Data Bit 3 or Data Bit 11 11 D10 Data Bit 10 12 D2 Data Bit 2 or Data Bit 10 12 D9 Data Bit 9 13 D1 Data Bit 1 or Data Bit 9 13 D8 Data Bit 8 14 D0 Data Bit 0 (LSB) or Data Bit 8 14 D7 Data Bit 7 15 A1 Address Input 1 15 D6 Data Bit 6 16 A0 Address Input 0 16 D5 Data Bit 5 17 WR Write Input. Active low. 17 D4 Data Bit 4 18 CS Chip-Select Input. Active low. 18 D3 Data Bit 3 19 VDD +12V to +15V Supply-Voltage Input 19 D2 Data Bit 2 VSS Bias pin for high-temperature, low-leakage configuration 20 D1 Data Bit 1 21 D0 Data Bit 0 (LSB) 22 CSMSB 23 LDAC Asynchronous Load DAC Input. Active low. 24 CSLSB Chip-Select Least Significant Byte. Active low. 20 Digital Ground Chip-Select Most Significant Byte. Active low. 25 WR Write Input. Active low. 26 VDD +12V to +15V Supply-Voltage Input 27 VSS Bias pin for high-temperature, low-leakage configuration 28 N.C. No Connection. Not internally connected. _______________________________________________________________________________________ 5 MX7534/MX7535 __________Pin Description (MX7534) MX7534/MX7535 Microprocessor-Compatible, 14-Bit DACs t1 t1 t2 5V t2 CSMSB 0V A0,A1 t3 t1 t4 5V t2 0V DATA t5 t6 CS 5V 0V CSLSB t3 LDAC t4 t4 0V 5V WR t7 WR 0V 0V t t5 6 5V 5V 0V 5V t5 t6 DATA 5V 0V NOTES: 1) ALL INPUT-SIGNAL RISE AND FALL TIMES ARE MEASURED FROM 10% TO 90% OF +5V. tR = tF = 20ns. VIH + VIL 2) TIMING MEASUREMENT REFERENCE LEVEL IS 2 NOTES: 1) ALL INPUT-SIGNAL RISE AND FALL TIMES ARE MEASURED FROM 10% TO 90% OF +5V. tR = tF = 20ns. VIH + VIL 2) TIMING MEASUREMENT REFERENCE LEVEL IS 2 3) IF LDAC IS ACTIVATED PRIOR TO THE RISING EDGE OF WR, THEN IT MUST STAY LOW FOR t3 OR LONGER AFTER WR GOES HIGH. Figure 1a. MX7534 Timing Diagram Figure 1b. MX7535 Timing Diagram _______________Detailed Description g(VREF,N) is the Thevenin equivalent voltage generator due to the reference input voltage, VREF, and the transfer function of the R-2R ladder, N. Digital-to-Analog Section The basic MX7534/MX7535 digital-to-analog converter (DAC) circuit consists of a laser-trimmed, thin-film, 11-bit R-2R resistor array, a 3-bit segmented resistor array, and NMOS current switches, as shown in Figure 2. The three MSBs are decoded to drive switches A–G of the segmented array, and the remaining bits drive switches S0–S10 of the R-2R array. Binary weighted currents are switched to either AGNDF or IOUT, depending on the status of each input bit. The R-2R ladder current is one-eighth of the total reference input current. The remaining seven-eighths of the current flows in the segmented resistors, dividing equally among these seven resistors. The input resistance at REF is constant; therefore, it can be driven by a voltage or current source of positive or negative polarity. The MX7534/MX7535 are optimized for unipolar output operation (analog output from 0V to -V REF), although bipolar operation (analog output from +VREF to -VREF) is possible with some added external components. Figure 3 shows the equivalent circuit for the two DACs. COUT varies from about 90pF to 180pF, depending on the digital code. R0 denotes the DAC’S equivalent output resistance, which varies with the input code. 6 Digital Section All digital inputs are both TTL and 5V CMOS logic compatible. The digital inputs are protected from electrostatic discharge (ESD) with typical input currents of less than 1nA. To minimize power-supply currents, keep digital input voltages as close to 0V and 5V logic levels as possible. __________Applications Information Unipolar Operation (2-Quadrant Multiplication) Figures 4a and 4b show the circuit diagram for unipolar binary operation. With an AC input, the circuit performs 2-quadrant multiplication. The code table for Figure 4 is given in Table 2. Capacitor C1 provides phase compensation and helps prevent overshoot and ringing when high-speed op amps are used. Note that the output polarity is the inverse of the reference input. _______________________________________________________________________________________ Microprocessor-Compatible, 14-Bit DACs 2R REFF* 2R 2R 2R 2R 2R R 2R MX7534/MX7535 R REFS* R 2R 2R 2R 2R R/4 G F E D C B A S10 S9 S0 RFB IOUT AGNDS *NOTE: VALID FOR MX7535. IN MX7534, 0REFS AND 0REFF ARE REPLACED BY ONE PIN: REF. AGNDF Figure 2. Simplified Circuit Diagram Zero-Offset Adjustment (Figures 4a and 4b) R/4 RFB 1) Load the DAC register with all 0s. 2) Adjust the offset of amplifier A1 so that V0 (see figure) is at a minimum (i.e., ≤ 30µV). Gain Adjustment (Figures 4a and 4b) 1) Load the DAC register with all 1s. 2) Trim potentiometer R1 so that VOUT = -VIN 16383 16384 ( RO IOUT + g(VREF, N) ILEAKAGE COUT – AGNDS ) In fixed-reference applications, adjust full scale by omitting R1 and R2 and trimming the reference voltage magnitude. In many applications, the excellent Gain Tempco and Gain Error specifications eliminate the need for gain adjustment. However, if trims are required and the DAC is to operate over a wide temperature range, use low-tempco (>300ppm/°C) resistors. Bipolar Operation (4-Quadrant Multiplication) Bipolar or 4-quadrant operation is shown in Figures 5a and 5b. This configuration provides for offset binary coding. Table 4 shows DAC codes and the corresponding analog outputs for Figures 5a and 5b. With the DAC loaded to 10 0000 0000 0000, either adjust R1 for VOUT = 0V, or omit R1 and R2 and adjust the ratio of R5 and R6 for VOUT = 0V. Adjust the amplitude of VIN or vary the value of R7 for full-scale trimming. Resistors R5, R6, and R7 must be matched to 0.003%. Mismatch of R5 and R6 causes both offset and fullscale errors. For wide temperature range operation, use resistors of the same material so that their temperature coefficients match and track. AGNDF Figure 3. Equivalent Analog Output Circuit Table 1. MX7534 Logic States A1 A2 FUNCTION WR CS X 1 X X Device not selected (Note 1) 1 X X X No data transfer 0 0 0 0 DAC loaded directly from Data Bus (Note 2) 0 0 0 1 MS Input Register loaded from Data Bus 0 0 1 0 LS Input Register loaded from Data Bus 0 0 1 1 DAC Register loaded from Input Registers Note 1: X = Don’t Care. Note 2: When A1 = 0 and A0 = 0, all DAC registers are transparent. By placing all 0s or all 1s on the data inputs, the user can load the DAC to zero or full-scale output in one write operation. This simplifies system calibration. _______________________________________________________________________________________ 7 MX7534/MX7535 Microprocessor-Compatible, 14-Bit DACs R1 100Ω VIN A0 A1 CS WR 1 REF 16 R1 20Ω VDD 19 2 RFB R2 33Ω VIN C1 33pF LDAC 3 15 IOUT 18 MX7534 17 D7–D0 DGND 7–14 6 4 AGNDS AGNDF VSS CSMSB A1 WR VO 5 2 1 26 REFF REFS VDD 4 MX7535 24 8–21 Grounding Considerations Since IOUT and the output amplifier noninverting input are sensitive to offset voltages, connect nodes that must be grounded directly to a single-point ground through a separate, very-low-resistance path. Note that the output currents at IOUT and AGNDF vary with input code and create code-dependent error if these terminals are connected to ground (or a virtual ground) through a resistive path. To obtain high accuracy, it is important to use a proper grounding technique. The two AGND pins (AGNDF‚ AGNDS) provide flexibility in this respect. In Figures 4a and 4b, AGNDS and AGNDF are shorted together externally and an extra op amp, A2, is not used. Voltage-drops due to bond-wire resistance are not compensated for in this circuit; this could create a linearity error of approximately 0.1LSB due to bond-wire resistance alone. This can be eliminated by using the circuits shown in Figures 6a and 6b, where A2 maintains AGNDS at signal ground potential. By using force/sense techniques, all switch contacts on the DAC are kept at exactly the same potential, and any error caused by bond-wire resistance is eliminated. Figure 7 shows a remote voltage reference driving the MX7535. Op amps A2 and A3 compensate for voltage drops along the reference input line and analog ground line. Figure 8 shows a printed circuit board (PCB) layout with a single output amplifier for the MX7534. The input to REF (Pin 1) is shielded to reduce AC feedthrough, while the digital inputs are shielded to minimize digital C1 33pF IOUT 25 ANALOG GROUND Figure 4a. Unipolar Binary Operation 3 RFB 22 D13–DO DGND 20 INPUT DATA 8 CSLSB 23 R2 10Ω AGNDF VSS 7 A1 5 AGNDS VO 6 27 ANALOG GROUND INPUT DATA Figure 4b. Unipolar Binary Operation Table 2. Unipolar Binary Code Table BINARY NUMBER IN DAC REGISTER ANALOG OUTPUT (VOUT) MSB 11 1111 1111 LSB 1111 10 0000 0000 0000 00 0000 0000 0001 00 0000 0000 0000 ( ( ( ) ) ) -VIN 16383 16384 1 -VIN 8192 = - VIN 16384 2 1 -VIN 16384 0V feedthrough. The traces connecting IOUT and AGNDS to the inverting and noninverting op amp inputs are kept as short as possible. Gain trim components, R3 and R4, are omitted. Zero-Offset Adjustment (Figures 6a and 6b) 1) Load DAC register with all 0s. 2) Adjust offset of amplifier A2 for minimum potential at AGNDS. This potential should be ≤30µV with respect to signal ground. 3) Adjust A1’s offset so that V OUT is at a minimum (i.e., ≤30µV). _______________________________________________________________________________________ Microprocessor-Compatible, 14-Bit DACs MX7534/MX7535 VIN VIN A0 A1 CS WR 16 R2, 33Ω VDD R1 100Ω 1 19 REF 2 RFB R5 10k IOUT 18 MX7534 7–14 6 + AGNDS AGNDF D7–D0 DGND VSS 5 R7 20k LDAC 3 15 17 C1 33pF R1 20Ω R6 20k CSMSB A1 R8, 5k,10% 4 + WR A2 VO CSLSB 20 ANALOG GROUND INPUT DATA 23 R2 10Ω VDD 1 26 3 2 REFF REFS RFB 24 IOUT MX7535 + AGNDS AGNDF D13–D0 DGND VSS 6 7 27 8–21 A1 A2 R8, 5k,10% 5 + VO ANALOG GROUND INPUT DATA Figure 5a. Bipolar Operation R7 20k R5 10k 4 22 25 R6 20k C1 33pF Figure 5b. Bipolar Operation Gain Adjustment (Figures 6a and 6b) 1) Load DAC register with all 1s. 2) Trim potentiometer R3 so that VOUT = - 16383 VIN 16384 ( ) Table 3. MX7535 Logic States FUNCTION CSMSB CSLSB LDAC WR 0 1 1 0 1 0 1 0 Load LS Input Register Low-Leakage Configuration Leakage current in the DAC flowing into the IOUT line can cause gain, linearity, and offset errors. Leakage is worse at high temperatures. Negatively bias VSS for a high-temperature, low-leakage configuration. Load MS Input Register 0 0 1 0 Load LS and MS Input Registers 1 1 0 X Load DAC Register from Input Register 0 0 0 0 All registers are transparent. Dynamic Considerations 1 1 1 X No operation In static or DC applications, the output amplifier’s AC characteristics are not critical. In higher-speed applications, where either the reference input is an AC signal or the DAC output must quickly settle to a new programmed value, the output op amp’s AC parameters must be considered. Another error source in dynamic applications is the parasitic signal coupling from the REF terminal to IOUT. This is normally a function of board layout and lead-tolead package capacitance. Signals can also be injected into the DAC outputs when the digital inputs are switched. This digital feedthrough depends on circuitboard layout and on-chip capacitive coupling. Minimize layout-induced feedthrough with guard traces between digital inputs, REF, and DAC outputs. X X 1 1 No operation Note: X = Don’t Care. Table 4. Offset Binary Bipolar Code Table BINARY NUMBER IN DAC REGISTER Analog Output (VOUT) MSB 11 1111 1111 LSB 1111 10 0000 0000 0001 10 0000 0000 0000 0 01 1111 1111 1111 -VIN 00 0000 0000 0000 -VIN ( ( ) ) +VIN 8191 8192 1 +VIN 8192 1 (8192 ) 8192 = -V (8192) IN _______________________________________________________________________________________ 9 MX7534/MX7535 Microprocessor-Compatible, 14-Bit DACs VDD VDD R3 100Ω R4 33Ω 1 19 2 REF VDD RFB C1 33pF 3 MX7534 D7–D0 DGND VSS 6 20 7–14 2 1 26 3 REFF REFS VDD RFB 4 VOLTAGE REFERENCE RL VO 4 5 C1 33pF IOUT AGNDS AGNDF R2 10Ω A1 + IOUT VIN R1 20Ω MX7535 + INPUT DATA A1 AGNDS AGNDF D13–D0 DGND VSS 6 7 27 8–21 A2 + RL VO 5 A2 + SIGNAL GROUND INPUT DATA SIGNAL GROUND NOTE: CONTROL INPUTS OMITTED FOR CLARITY. NOTE: CONTROL INPUTS OMITTED FOR CLARITY. Figure 6a. Unipolar Binary Operation with Forced Ground ANALOG GROUND Figure 6b. Unipolar Binary Operation with Forced Ground for Remote Load Table 5. Amplifier Performance Comparisons OP AMP INPUT OFFSET VOLTAGE (VOS) INPUT BIAS CURRENT (IB) OFFSET VOLTAGE DRIFT (TC VOS) SETTLING TO 0.003% FS MAX400 10µV 2nA 0.3µV/°C 50µs Maxim OP07 25µV 2nA 0.6µV/°C 50µs AD554L* 500µV 25pA 5µV/°C 5µs HA2620* 4mV 35nA 20µV/°C 0.8µs * AD544L is an Analog Devices part; HA2620 is a Harris Semiconductor part. Compensation A compensation capacitor, C1, may be needed when the DAC is used with a high-speed output amplifier. The capacitor cancels the pole formed by the DAC’s output capacitance and internal feedback resistance. Its value depends on the type of op amp used, but typical values range from 10pF to 33pF. Too small a value causes output ringing, while excess capacitance overdamps the output. Minimize C1’s size and improve output settling performance by keeping the PC board trace as short as possible and stray capacitance at IOUT as small as possible. Bypassing Place a 1µF bypass capacitor, in parallel with a 0.01µF ceramic capacitor, as close to the DAC’s VDD and GND pins as possible. Use a 1µF tantalum bypass capacitor to optimize high-frequency noise rejection. Place a 4.7µF decoupling capacitor at VSS to minimize the DAC output leakage current. 10 The MX7534/MX7535 have high-impedance digital inputs. To minimize noise pickup, connect them to either VDD or GND terminals when not in use. Connect active inputs to VDD or GND through high-value resistors (1MΩ) to prevent static charge accumulation if these pins are left floating, as might be the case when a circuit card is left unconnected. Op-Amp Selection Input offset voltage (VOS), input bias current (IB), and offset voltage drift (TC VOS) are three key parameters in determining the choice of a suitable amplifier. To maintain specified accuracy with VREF of 10V, VOS should be less than 30µV and IB should be less than 2nA. Open-loop gain should be greater than 340,000. Maxim’s MAX400 has low V OS (10µV max), low I B (2nA), and low TC VOS (0.3µV/°C max). This op amp can be used without requiring any adjustments. For ______________________________________________________________________________________ Microprocessor-Compatible, 14-Bit DACs + A2 2 1 REFF REFS 26 MX7534/MX7535 V+ VPIN 1 AD544* VDD 3 C1 33pF VDD RFB OUTPUT 4 IOUT MX7535 + AGNDS AGNDF D13–D0 DGND VSS 6 7 27 8–21 C1 LOCATION A1 5 RL V0 REF VSS VDD INPUT DATA PIN 1 MX7534 A3 AGND + DGND NOTE: CONTROL INPUTS OMITTED FOR CLARITY. Figure 7. Driving the MX7535 with a Remote Voltage Reference medium-frequency applications, the OP27 is recommended. For higher-frequency applications, the HA2620 is recommended. However, these op amps require external offset adjustment (Table 5). ________Microprocessor Interfacing NOTE: LAYOUT IS FOR DOUBLE-SIDED PCB. BOLD LINE INDICATES TRACK ON COMPONENT SIDE. *AD544 IS AN ANALOG DEVICES PART. Figure 8. Suggested Layout for MX7534 Incorporating Output Amplifier 8086 with MX7535 The MX7534/MX7535 interface to both 8-bit and 16-bit processors. Figure 9a shows the 8086 16-bit processor interfacing to a single MX7535. In this setup, the doublebuffering feature of the DAC is not used. AD0–AD13 of the 16-bit data bus are connected to the DAC data bus (D0–D13). The 14-bit word is written to the DAC in one MOV instruction, and the analog output responds immediately. In this example, the DAC address is D000. Table 6a shows a software routine for Figure 9a. In a multiple DAC system, the double buffering of the DAC chips allows the user to simultaneously update all DACs. In Figure 10, a 14-bit word is loaded to each of the DAC’s input registers in sequence. Then, with one instruction to the appropriate address, CS4 (i.e., LDAC) is brought low, updating all the DACs simultaneously. 8086 with MX7534 14-bit word is loaded in two bytes, using the MOV instruction. A further MOV loads the DAC register and causes the analog data to appear at the converter output. For the example given here, the appropriate DAC register addresses are D002, D004, and D006. Table 6b shows the program for loading the DAC. 8085A with MX7534 A typical interface circuit is shown in Figure 9c. The DAC is treated as four memory locations addressed by A0 and A1. In standard operation, three of these memory locations are used. Table 6c shows a sample program for loading the DAC with a 14-bit word. The MX7534 has address locations 3000–3003. The six MSBs are written into location 3001, and eight LSBs are written to 3002. Then, with a write instruction to 3003, the full 14-bit word is loaded to the DAC register. Figure 9b shows an interface circuit to a 16-bit microprocessor. The bottom 8 bits (AD0–AD7) of the 16-bit data bus are connected to the DAC data bus. The ______________________________________________________________________________________ 11 MX7534/MX7535 Microprocessor-Compatible, 14-Bit DACs MC68000 with MX7535 Figure 11a shows an interface diagram. The following routine writes data to the DAC input registers and then outputs the data via the DAC register: 01000 MOVE.W #W,D0 DAC data, W, loaded into Data Register 0. MOVE.W D0,$E000 Data W transferred between D0 and DAC Register. MOVE.B #228,D7 Control returned to the System. TRAP #14 Monitor Program ADDRESS BUS ALE 16-BIT LATCH ADDRESS DECODE CSMSB CSLSB LDAC 8086 MX7535* WR WR AD13 DATA BUS AD0–AD15 D0–D13 AD0 *SOME CIRCUITRY OMITTED FOR CLARITY MC68000 with MX7534 Figure 11b shows the MC68000 interface diagram. The following routine writes data to the DAC input registers and then outputs the data via the DAC register: .A2 E003 Address Register 2 loaded with E003. 01000 MOVE.W #W,D0 DAC data, W, loaded into Data Register 0. MOVEP.W D0,$0000(A2) Data W transferred between D0 and the DAC’s Input Register. High-ordered byte transferred first. Memory address specified using the address register indirect plus displacement addressing mode. Address used here (E003) is odd, so data is transferred on the loworder half of the data bus (D0–D7). MOVE.W D0,$E006 This instruction provides appropriate signals to transfer data W from the DAC Input Register to the DAC Register, which controls the R-2R ladder switches. MOVE.B #228,D7 Control returned to the System. TRAP #14 Monitor Program Since this interfacing system uses only the lower half of the data bus, it is also suitable for use with the MC68008, which provides the user with an 8-bit data bus instead of the MC68000’s 16-bit bus. 12 Figure 9a. MX7535—8086 Interface Circuit ADDRESS BUS ADDRESS BUS A2 ALE 16-BIT LATCH ADDRESS DECODE A1 A1 A0 CS MX7534* 8086 WR WR D0–D7 DATA BUS AD0–AD15 *SOME CIRCUITRY OMITTED FOR CLARITY Figure 9b. MX7534—8086 Interface Circuit ADDRESS BUS A8–A15 AE LATCH ADDRESS DECODE MX7534* 8085A WR AD0–AD7 A1 A0 CS WR DATA BUS *SOME CIRCUITRY OMITTED FOR CLARITY Figure 9c. MX7534—8085A Interface Circuit ______________________________________________________________________________________ D0–D7 Microprocessor-Compatible, 14-Bit DACs MX7534/MX7535 Table 6a. Sample Program for Loading the MX7535 00 02 04 07 0B 0E ASSUME DS:DACLOAD,CS:DACLOAD DACLOAD SEGMENT AT 000 8CC9 MOV CX,CS 8ED9 MOVDS,CX BF00D0 MOVDI,#D000 C705“YZWX” MOV MEM,#YZWX EA0000 00FF :DEFINE DATA SEGMENT REGISTER EQUAL :TO CODE SEGMENT REGISTER :LOAD DI WITH D000 :DAC LOADED WITH WXYZ :CONTROL IS RETURNED TO THE MONITOR PROGRAM Table 6b. Sample Program for Loading the MX7534 from 8086 00 02 04 07 0A 0B 0C 0F 10 11 14 ASSUME DS:DACLOAD,CS:DACLOAD DACLOAD SEGMENT AT 000 8CC9 MOV CX,CS MOVDS,CX 8ED9 BF02D0 MOVDI.#D002 MOV MEM,#“MS” C605“MS” 47 INC DI 47 INC DI C605“LS” MOV MEM,#“LS” INC DI 47 47 INC DI MOV MEM,#00 C60500 JMP MEM EA0000 :DEFINE DATA SEGMENT REGISTER EQUAL :TO CODE SEGMENT REGISTER :LOAD DI WITH D002 :DAC LOADED WITH “MS” :LS INPUT REGISTER LOADED WITH “LS” :CONTENT OF INPUT REGISTERS ARE LOADED TO THE DAC REGISTER :CONTROL IS RETURNED TO THE MONITOR PROGRAM Table 6c. Sample Program for Loading the MX7534 from 8085A 2000 01 02 03 04 05 06 07 08 09 0A 0B 0C 200D 26 30 2E 01 3E “MS” 77 2C 3E “LS” 77 2C 77 CF MVIH,#30 MVIL,#01 MVIA,#“MS” MOV M,A INR L MVI A#“LS” MOV M,A INR L MOV M,A RST I Z80 with MX7534/MX7535 Figure 12a is an interface circuit for the Z80, using the MX7535. This is an example of an 8-bit processor interface for these DACs. Figure 12b shows the schematic for the MX7534. MC6809 with MX7534 Figure 13a shows an interface circuit that enables the MX7534 to be programmed using the MC6809 8-bit microprocessor. Use the 16-bit D accumulator to simplify data transfer. The two key processor instructions are: LDD Load D accumulator from memory STD Store D accumulator to memory MC6502 with MX7534 Figure 13b shows an interface diagram for the MC6502 using the MX7534. ________________Digital Feedthrough In the interface diagrams shown in Figures 9–13, the digital inputs of the DAC are directly connected to the microprocessor bus. Even when the device is not selected, activity on the bus can feed through on the DAC output through package capacitance and appear as noise. To minimize noise, isolate the DACs from the digital bus, as shown in Figures 14a and 14b. ______________________________________________________________________________________ 13 MX7534/MX7535 Microprocessor-Compatible, 14-Bit DACs ADDRESS BUS ALE 8086 16-BIT LATCH ADDRESS DECODE A1–A23 CS1 CS4 CS3 CS2 WR CSMSB CSLSB LDAC AS ADDRESS BUS ADDRESS DECODE CSMSB CSLSB LDAC MC68000 DTACK WR MX7535* R/W MX7535* AD0–AD15 DATA BUS WR D0–D15 DATA BUS D0–D13 D0–D13 CSMSB CSLSB *SOME CIRCUITRY OMITTED FOR CLARITY Figure 11a. MX7535—MC68000 Interface LDAC WR MX7535* ADDRESS BUS A1–A23 A1 D0–D13 AS MC68000 CSMSB CSLSB LDAC WR MX7535* A0 ADDRESS DECODE CS MX7534* DTACK WR D0–D7 R/W D0–D7 DATA BUS D0–D13 *SOME CIRCUITRY OMITTED FOR CLARITY *SOME CIRCUITRY OMITTED FOR CLARITY Figure 11b. MX7534—MC68000 Interface Figure 10. MX7535—8086 Interface: Multiple DAC Systems 14 A2 A1 ______________________________________________________________________________________ Microprocessor-Compatible, 14-Bit DACs CSLSB CSMSB LDAC ADDRESS DECODE MREQ A0–A15 Z80 MREQ A0 A1 CS MX7534* D0–D7 DATA BUS ADDRESS DECODE WR WR D8–D13 D8–D7 ADDRESS BUS Z80 MX7535* WR MX7534/MX7535 ADDRESS BUS A0–A15 WR DATA BUS D0–D7 D0–D7 *SOME CIRCUITRY OMITTED FOR CLARITY *SOME CIRCUITRY OMITTED FOR CLARITY Figure 12a. MX7535—Z80 Interface Figure 12b. MX7534—Z80 Interface ADDRESS BUS A0–A15 R/W Q E ADDRESS DECODE A0–A15 A0 A1 R/W CS MX7534* WR ADDRESS ADDRESS BUS BUS ADDRESS DECODE 6502 A0 A1 CS MX7534* ∅2 WR MC6809 D0–D7 DATA BUS D0–D7 Figure 13a. MX7534—MC6809 Interface Circuit WR MICROPROCESSOR SYSTEM D0–D7 Figure 13b. MX7534—6502 Interface ADDRESS DECODE A0 DATA BUS *SOME CIRCUITRY OMITTED FOR CLARITY *SOME CIRCUITRY OMITTED FOR CLARITY A0–A15 D0–D7 A0–A15 ADDRESS DECODE A1 EN QUAD LATCH EN QUAD LATCH A1 CS A0 WR MICROPROCESSOR SYSTEM EN MX7534* WR D0–D7 D0–D7 EN QUAD LATCH *SOME CIRCUITRY OMITTED FOR CLARITY Figure 14a. MX7534—Interface Circuit Using Latches to Minimize Digital Feedthrough 16-BIT LATCH CSMSB CSLSB LDAC WR MX7535* D0–D15 D0–D13 *SOME CIRCUITRY OMITTED FOR CLARITY Figure 14b. MX7535—Interface Circuit Using Latches to Minimize Digital Feedthrough ______________________________________________________________________________________ 15 MX7534/MX7535 Microprocessor-Compatible, 14-Bit DACs ___Functional Diagrams (continued) TOP VIEW VDD 26 1 REFS 2 REFF MX7535 3 4 5 6 23 14-BIT DAC 14 DAC REGISTER 6 MS INPUT REGISTER 8 LS INPUT REGISTER 8–21 D13–D0 24 7 DGND _____Pin Configurations (continued) 28 N.C. REFS 1 RFB IOUT AGNDS AGNDF LDAC REFF 2 27 VSS RFB 3 26 VDD IOUT 4 25 WR AGNDS 5 CSLSB AGNDF 6 22 CSMSB 25 WR DGND 7 (MSB) D13 8 27 VSS _Ordering Information (continued) PART TEMP. RANGE PIN PACKAGE INL (LSBs) MX7535KN MX7535JN MX7535KCWI MX7535JCWI MX7535KP MX7535JP MX7535J/D MX7535BQ MX7535AQ MX7535BD MX7535AD MX7535KEWI MX7535JEWI MX7535TQ MX7535SQ MX7535TD MX7535SD 0°C to +70°C 0°C to +70°C 0°C to +70°C 0°C to +70°C 0°C to +70°C 0°C to +70°C 0°C to +70°C -25°C to +85°C -25°C to +85°C -25°C to +85°C -25°C to +85°C -40°C to +85°C -40°C to +85°C -55°C to +125°C -55°C to +125°C -55°C to +125°C -55°C to +125°C 28 Plastic DIP 28 Plastic DIP 28 Wide SO 28 Wide SO 28 PLCC 28 PLCC Dice* 28 CERDIP 28 CERDIP 28 Ceramic SB 28 Ceramic SB 28 Wide SO 28 Wide SO 28 CERDIP 28 CERDIP 28 Ceramic SB 28 Ceramic SB ±1 ±2 ±1 ±2 ±1 ±2 ±2 ±1 ±2 ±1 ±2 ±1 ±2 ±1 ±2 ±1 ±2 MX7535 24 CSLSB 23 LDAC 22 CSMSB 21 D0 (LSB) D12 9 20 D1 D11 10 19 D2 D10 11 18 D3 D9 12 17 D4 D8 13 16 D5 D7 14 15 D6 DIP/SO/PLCC/Ceramic SB *Dice are tested at +25°C, DC parameters only. Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. 16 __________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 (408) 737-7600 © 1996 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.