19-0257; Rev 3; 12/95 Octal, 13-Bit Voltage-Output DAC with Parallel Interface _____________________________Features The MAX547 contains eight 13-bit, voltage-output digital-toanalog converters (DACs). On-chip precision output amplifiers provide the voltage outputs. The MAX547 operates from a ±5V supply. Bipolar output voltages with up to ±4.5V voltage swing can be achieved with no external components. The MAX547 has four separate reference inputs; each is connected to two DACs, providing different fullscale output voltages for every DAC pair. The MAX547 features double-buffered interface logic with a 13-bit parallel data bus. Each DAC has an input latch and a DAC latch. Data in the DAC latch sets the output voltage. The eight input latches are addressed with three address lines. Data is loaded to the input latch with a single write instruction. –——– An asynchronous load (LD_ ) input transfers data from the –—— – input latch to the DAC latch. The four LD_ inputs each control two DACs, and all DAC latches can be updated simultane–——– –——– ously by asserting all LD_ pins. An asynchronous clear (CLR) input resets the output of all eight DACs to AGND_. Asserting –——– CLR resets both the DAC and the input latch to bipolar zero (1000hex). On power-up, reset circuitry performs the same –——– function as CLR. All logic inputs are TTL/CMOS compatible. The MAX547 is available in 44-pin plastic quad flat pack and 44-pin PLCC packages. ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ________________________Applications Automatic Test Equipment Minimum Component-Count Analog Systems Digital Offset/Gain Adjustment Arbitrary Function Generators Industrial Process Controls Avionics Equipment Full 13-Bit Performance without Adjustments 8 DACs in One Package Buffered Voltage Outputs Calibrated Linearity Guaranteed Monotonic to 13 Bits ±5V Supply Operation Unipolar or Bipolar Outputs Swing to ±4.5V Fast Output Settling (5µs to ±1⁄2LSB) Double-Buffered Digital Inputs Asynchronous Load Inputs Load Pairs of DAC Latches –——– Asynchronous C L R Input Resets DACs to Analog Ground ♦ Power-On Reset Circuit Resets DACs to Analog Ground ♦ Microprocessor and TTL/CMOS Compatible ________________Ordering Information PIN-PACKAGE INL (LSBs) PART TEMP. RANGE MAX547ACQH 0°C to +70°C 44 PLCC ±2 MAX547BCQH MAX547ACMH MAX547BCMH MAX547BC/D 0°C to +70°C 0°C to +70°C 0°C to +70°C 0°C to +70°C 44 PLCC 44 Plastic FP 44 Plastic FP Dice* ±4 ±2 ±4 ±4 Ordering Information continued at end of data sheet. *Contact factory for dice specifications. 32 3 31 4 30 5 29 6 28 MAX547 7 8 27 26 9 25 24 10 11 22 20 21 VOUTF 44 43 42 41 40 VOUTE 1 VSS 2 REFEF AGNDEF 3 AGNDCD 4 CLR VSS REFCD VOUTD 5 VOUTG VOUTH VDD REFGH AGNDGH GND LDGH LDEF D0 D1 D2 VOUTB 7 39 VOUTG VOUTA 8 38 VOUTH VDD 9 37 VDD REFAB 10 36 REFGH AGNDAB 11 LDAB 12 LDCD 13 33 LDGH CS 14 32 LDEF WR 15 31 D0 A2 16 30 D1 A1 17 29 D2 35 AGNDGH MAX547 34 GND PLASTIC FP D3 D4 D5 D6 D7 D8 D9 A0 D10 19 20 21 22 23 24 25 26 27 28 D11 18 D12 A0 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 17 18 19 23 14 15 16 6 34 35 36 37 38 39 40 42 41 33 2 12 LDAB LDCD CS WR A2 A1 1 13 VOUTB VOUTA VDD REFAB AGNDAB 43 44 VOUTC VOUTD VSS REFCD AGNDCD CLR AGNDEF REFEF VSS VOUTE VOUTF TOP VIEW VOUTC _______________________________________________________________Pin Configurations PLCC ________________________________________________________________ Maxim Integrated Products 1 For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800 MAX547 _________________General Description MAX547 Octal, 13-Bit Voltage-Output DAC with Parallel Interface ABSOLUTE MAXIMUM RATINGS VDD to GND ..............................................................-0.3V to +6V VSS to GND...............................................................-6V to +0.3V Digital Input Voltage to GND ......................-0.3V to (VDD + 0.3V) REF_ ..........................................(AGND_ - 0.3V) to (VDD + 0.3V) AGND_ .............................................(VSS - 0.3V) to (VDD + 0.3V) VOUT_ ........................................................................VDD to VSS Maximum Current into REF_ Pin .......................................±10mA Maximum Current into Any Other Signal Pin ....................±50mA Continuous Power Dissipation (TA = +70°C) PLCC (derate 13.33mW/°C above +70°C)...................1067mW Plastic FP (derate 11.11mW/°C above +70°C )..............889mW Operating Temperature Ranges MAX547–C–H.........................................................0°C to +70°C MAX547–E–H ......................................................-40°C to +85°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 = +5V, VSS = -5V, REF_ = 4.096V, AGND_ = GND = 0V, RL = 10kΩ, CL = 50pF, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS STATIC PERFORMANCE—ANALOG SECTION Resolution N Relative Accuracy INL Differential Nonlinearity DNL 13 Bits MAX547A ±0.5 ±2 MAX547B ±0.5 ±4 Guaranteed monotonic LSB ±1 LSB Bipolar Zero-Code Error ±5 ±20 LSB Gain Error ±1 ±8 LSB Power-Supply Rejection Ratio PSRR ∆Gain/∆VDD (Note 1) ±0.0025 ∆Gain/∆VSS (Note 1) ±0.0025 RL = ∞ to 10kΩ Load Regulation 0.3 %/% LSB REFERENCE INPUT (Note 2) Reference Input Range Reference Input Resistance REF RREF (Notes 2, 3) Each REF– pin (Note 3) AGND– VDD 5 V kΩ ANALOG OUTPUT Maximum Output Voltage VDD - 0.5 V Minimum Output Voltage VSS + 0.5 V 3 V/µs DYNAMIC PERFORMANCE—ANALOG SECTION Voltage-Output Slew Rate To ±1⁄2 LSB of full scale (Note 4) Output Settling Time 5 µs Digital Feedthrough 5 nV-s Digital Crosstalk 5 nV-s DIGITAL INPUTS (VDD = 5V ±5%) Input Voltage High VIH Input Voltage Low VIL 0.8 V Input Current IIN VIN = 0V or VDD 1.0 µA Input Capacitance CIN (Note 5) 10 pF 2 2.4 _______________________________________________________________________________________ V Octal, 13-Bit Voltage-Output DAC with Parallel Interface (VDD = +5V, VSS = -5V, REF_ = 4.096V, AGND_ = GND = 0V, RL = 10kΩ, CL = 50pF, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS POWER SUPPLIES Positive Supply Range VDD (Note 6) 4.75 5.25 V Negative Supply Range VSS (Note 6) -5.25 -4.75 V Positive Supply Current IDD TA = TMIN to TMAX 14 44 mA Negative Supply Current ISS TA = TMIN to TMAX 11 40 mA Note 1: PSRR is tested by changing the respective supply voltage by ±5%. Note 2: For best performance, REF_ should be greater than AGND_ + 2V and less than VDD - 0.6V. The device operates with reference inputs outside this range, but performance may degrade. For further information on the reference, see the Reference and Analog-Ground Inputs section in the Detailed Description. Note 3: Reference input resistance is code dependent. See Reference and Analog-Ground Inputs section in the Detailed Description. Note 4: Typical settling time with 1000pF capacitive load is 10µs. Note 5: Guaranteed by design. Not production tested. Note 6: Guaranteed by supply-rejection test. TIMING CHARACTERISTICS (VDD = +5V, VSS = -5V, REF_ = 4.096V, AGND_ = GND = 0V, TA = TMIN to TMAX, unless otherwise noted.) PARAMETER –—– CS Pulse Width Low –—– WR Pulse Width Low –—— – LD– Pulse Width Low –——– CLR Pulse Width Low –—– –—– CS Low to WR Low –—– –—– CS High to WR High –—– Data Valid to WR Setup –—– Data Valid to WR Hold –—– Address Valid to WR Setup –—– Address Valid to WR Hold SYMBOL CONDITIONS MIN TYP MAX UNITS t1 50 ns t2 50 ns t3 50 ns t4 100 ns t5 0 ns t6 0 ns t7 50 ns t8 0 ns t9 10 ns t10 0 ns _______________________________________________________________________________________ 3 MAX547 ELECTRICAL CHARACTERISTICS (continued) __________________________________________Typical Operating Characteristics (VDD = 5V, VSS = -5V, REF_ = 4.096V, AGND_ = GND = 0V, TA = +25°C, unless otherwise noted.) 0.2 0.1 0 -0.1 -0.2 1 0 -0.3 20 15 5 0 -5 ISS -10 -15 -20 -2 1 TOTAL HARMONIC DISTORTION + NOISE AT DAC OUTPUT vs. REFERENCE FREQUENCY SETTLING TIME vs. LOAD CAPACITANCE REF– = 2Vp-p INPUT CODE = ALL 1s 0.060 0.050 0.040 0.080 0.070 REF– = 4Vp-p INPUT CODE = ALL 1s 0.060 0.050 0.040 0.030 0.030 0.020 0.020 0.010 0.010 1000 SETTLING TIME (µs) 0.070 0.090 THD + NOISE (%) 0.080 FREQUENCY (kHz) 10 100 FREQUENCY (kHz) REFERENCE INPUT SMALL-SIGNAL FREQUENCY RESPONSE REFERENCE INPUT LARGE-SIGNAL FREQUENCY RESPONSE 100 1 1000 2 0 MAX547-Fg TOC-1 6 0 -2 RELATIVE OUTPUT (dB) SINE WAVE AT REF– 2V ±100mV CODE ALL 1s -6 -12 -18 -24 -14 -22 100 FREQUENCY (kHz) 1000 10,000 1 10 100 0 -10 -20 -30 -40 SINE WAVE AT REF_ 2V ±2V -50 -60 -70 -36 10 0.1 REFERENCE FEEDTHROUGH -10 -18 1 0.01 LOAD CAPACITANCE (nF) SINE WAVE AT REF_ 2V ±2V CODE ALL 1s -6 -30 0.1 10 1000 RELATIVE OUTPUT (dB) 10 MAX547-Fg TOC-6 1 100 1 0 0 20 40 60 80 100 120 140 TEMPERATURE (°C) MAX547-Fg TOC-3 0.090 -60 -40 -20 0 5 4 0.100 MAX547-Fg TOC-4 0.100 3 REFERENCE VOLTAGE (V) DIGITAL INPUT CODE (DECIMAL) TOTAL HARMONIC DISTORTION + NOISE AT DAC OUTPUT vs. REFERENCE FREQUENCY 2 MAX547-Fg TOC-9 0 MAX547-Fg TOC-7 8191 7168 6144 5120 3072 4096 2048 1024 0 -0.5 THD + NOISE (%) IDD 10 -1 -0.4 4 MAX547-Fg TOC-2 2 RELATIVE ACCURACY (LSB) 0.3 3 MAX547-Fg TOC-11 0.4 SUPPLY CURRENT (mA) MAX547-Fg TOC-5 0.5 RELATIVE ACCURACY (LSB) SUPPLY CURRENT vs. TEMPERATURE RELATIVE ACCURACY vs. REFERENCE VOLTAGE RELATIVE ACCURACY vs. DIGITAL INPUT CODE RELATIVE OUTPUT (dB) MAX547 Octal, 13-Bit Voltage-Output DAC with Parallel Interface -80 -90 0.1 1 10 100 1000 FREQUENCY (kHz) 10,000 0.1 1 10 100 FREQUENCY (kHz) _______________________________________________________________________________________ 1000 Octal, 13-Bit Voltage-Output DAC with Parallel Interface POWER-SUPPLY REJECTION RATIO vs. FREQUENCY VDD = VSS = 5V ±200mV NO LOAD NEGATIVE FULL-SCALE 1.0 -30 VSS ERROR (LSB) PSRR (dB) -20 1.5 VDD -40 -50 MAX547-Fg TOC-8 -10 2.0 MAX547-Fg TOC-10 0 FULL-SCALE ERROR vs. LOAD RESISTANCE 0.5 0 REF_ = 4.096V -0.5 -60 -1.0 -70 -1.5 POSITIVE FULL-SCALE -2.0 -80 0.01 0.1 1 10 100 1000 1 FREQUENCY (kHz) 100 10 1000 LOAD RESISTANCE (kΩ) NEGATIVE SETTLING TIME TO FULL-SCALE STEP (ALL BITS ON TO ALL BITS OFF) POSITIVE SETTLING TIME TO FULL-SCALE STEP (ALL BITS OFF TO ALL BITS ON) DIGITAL INPUTS (5V/div) DIGITAL INPUTS (5V/div) OUTPUT (1mV/div) OUTPUT (1mV/div) 2µs/div REF– = 4.096V, CL = 100pF, RL = 5kΩ 2µs/div REF– = 4.096V, CL = 100pF, RL = 5kΩ DYNAMIC RESPONSE (ALL BITS OFF, ON, OFF) DIGITAL FEEDTHROUGH (GLITCH IMPULSE) DIGITAL INPUTS (5V/div) +5V 0V 10mV 0V -10mV OUTPUT (2V/div) 2µs/div REF– = 4.096V, CL = 100pF, RL = 5kΩ 200ns/div TOP: DIGITAL TRANSITION ON ALL DATA BITS BOTTOM: DAC OUTPUT WITH WR HIGH 10mV/div _______________________________________________________________________________________ 5 MAX547 ____________________________Typical Operating Characteristics (continued) (VDD = 5V, VSS = -5V, REF_ = 4.096V, AGND_ = GND = 0V, TA = +25°C, unless otherwise noted.) MAX547 Octal, 13-Bit Voltage-Output DAC with Parallel Interface ____________________________Typical Operating Characteristics (continued) (VDD = 5V, VSS = -5V, REF_ = 4.096V, AGND_ = GND = 0V, TA = +25°C, unless otherwise noted.) ADJACENT-CHANNEL CROSSTALK ADJACENT-CHANNEL CROSSTALK A: 5V/div A 5V/div B 5mV/div 500ns/div REF– = 4.096V, CL = 50pF, RL = 10kΩ A: DIGITAL INPUTS, DAC A, DATA BITS from ALL Os to OAAAhex B: OUTPUT, DAC B B: 5mV/div 500ns/div REF– = 4.096V, CL = 50pF, RL = 10kΩ A: DIGITAL INPUTS, DAC A, DATA BITS from OAAAhex to ALL Os B: OUTPUT, DAC B ______________________________________________________________Pin Description PIN 6 NAME FUNCTION PLCC FLAT PACK 1 39 –——– CLR 2 40 AGNDCD 3 41 REFCD 4, 42 42, 36 VSS 5 43 VOUTD DAC D Output Voltage 6 44 VOUTC DAC C Output Voltage 7 1 VOUTB DAC B Output Voltage 8 2 VOUTA DAC A Output Voltage 9, 37 3, 31 VDD Positive Power Supply, 5V (2 pins). Connect both pins to the supply voltage. Bypass each pin to the system analog ground with a 0.1µF to 1µF capacitor. 10 4 REFAB Reference Voltage Input for DAC A and DAC B. Bypass to AGNDAB with a 0.1µF to 1µF capacitor. 11 5 AGNDAB 12 6 –———– LDAB Load Input (active low). Driving this asynchronous input low transfers the contents of input latches A and B to the respective DAC latches. 13 7 –———– LDCD Load Input (active low). Driving this asynchronous input low transfers the contents of input latches C and D to the respective DAC latches. 14 8 15 9 –—– CS –—– WR Clear Input (active low). Driving this asynchronous input low sets the content of all latches to 1000hex. All DAC outputs are reset to AGND_. Analog Ground for DAC C and DAC D Reference Voltage Input for DAC C and DAC D. Bypass to AGNDCD with a 0.1µF to 1µF capacitor. Negative Power Supply, -5V (2 pins). Connect both pins to the supply voltage. Bypass each pin to the system analog ground with a 0.1µF to 1µF capacitor. Analog Ground for DAC A and DAC B Chip Select (active low) –—– –—– Write Input (active low). WR, along with CS, loads data into the DAC input latch selected by A0–A2. _______________________________________________________________________________________ Octal, 13-Bit Voltage-Output DAC with Parallel Interface PIN PLCC FLAT PACK NAME FUNCTION 16 10 A2 Address Bit 2 17 11 A1 Address Bit 1 18 12 A0 Address Bit 0 19–31 13–25 D12–D0 Data Bits 12–0 32 26 –———– LDEF Load Input (active low). Driving this asynchronous input low transfers the contents of input latches E and F to the respective DAC latches. 33 27 –———– LDGH Load Input (active low). Driving this asynchronous input low transfers the contents of input latches G and H to the respective DAC latches. 34 28 GND Digital Ground 35 29 AGNDGH 36 30 REFGH Reference Voltage Input for DAC G and DAC H. Bypass to AGNDGH with a 0.1µF to 1µF capacitor. 38 32 VOUTH DAC H Output Voltage 39 33 VOUTG DAC G Output Voltage 40 34 VOUTF DAC F Output Voltage 41 35 VOUTE DAC E Output Voltage 43 37 REFEF 44 38 AGNDEF Analog Ground for DAC G and DAC H Reference Voltage Input for DAC E and DAC F. Bypass to AGNDEF with a 0.1µF to 1µF capaciAnalog Ground for DAC E and DAC F _______________Detailed Description Analog Section The MAX547 contains eight 13-bit, voltage-output DACs. These DACs are “inverted” R-2R ladder networks that convert 13-bit digital inputs into equivalent analog output voltages, in proportion to the applied reference voltages. The MAX547 has one reference input (REF_) and one analog-ground input (AGND_) for each pair of DACs. The four REF_ inputs allow different fullscale output voltages for each DAC pair, and the four AGND_ inputs allow different offset voltages for each DAC pair. The DAC ladder outputs are buffered with op amps that operate with a gain of two. The inverting node of the amplifier is connected to the respective reference input, resulting in bipolar output voltages from -REF_ to 4095/4096 REF_. Figure 1 shows the simplified DAC circuit. R R 2R R R R VDAC 2R 2R 2R 2R D0 D10 D11 D12 OUT REF– AGND– Figure 1. DAC Simplified Circuit Diagram _______________________________________________________________________________________ 7 MAX547 _________________________________________________Pin Description (continued) MAX547 Octal, 13-Bit Voltage-Output DAC with Parallel Interface Reference and Analog-Ground Inputs The REF_ inputs can range between AGND_ and VDD. However, the DAC outputs will operate to VDD - 0.6V and VSS + 0.6V, due to the output amplifiers’ voltageswing limitations. The AGND_ inputs can be offset by any voltage within the supply rails. The offset-voltage potential must be lower than the reference-voltage potential. For more information, refer to the Digital Code and Analog Output Voltage section in the Applications Information. The input impedance of the REF_ inputs is code dependent. It is at its lowest value (5kΩ min) when the input code of the referring DAC pair is 0 1010 1010 1010 (0AAAhex). Its maximum value, typically 50kΩ, occurs when the code is 0000hex. When all reference inputs are driven from the same source, the minimum load impedance is 1.25kΩ. Since the input impedance at REF_ is code dependent, load regulation of the reference used is important. For more information, see Reference Selection in the Applications Information section. The input capacitance at REF_ is also code dependent, and typically varies from 125pF to 300pF. Its minimum value occurs when the code of the referring DAC pair is set to all 0s. It is at its maximum value with all 1s on both DACs. Output Buffer Amplifiers The MAX547’s voltage outputs are internally buffered by precision gain-of-two amplifiers with a typical slew rate of 3V/µs. With a full-scale transition at its output, the typical settling time to ±1⁄2LSB is 5µs when loaded with 10kΩ in parallel with 50pF, or 6µs when loaded with 10kΩ in parallel with 100pF. Digital Inputs and Interface Logic All digital inputs are compatible with both TTL and CMOS logic. The MAX547 interfaces with microprocessors using a data bus at least 13 bits wide. The interface is double buffered, allowing simultaneous update of all DACs. There are two latches for each DAC (see Functional Diagram): an input latch that receives data from the data bus, and a DAC latch that receives data from the input latch. Address lines A0, A1, and A2 select which DAC’s input latch receives data from the data bus, as shown in Table 1. Transfer data from the input latches to the DAC latches by asserting the asynchronous LD_ signal. Each DAC’s analog output reflects the data held in its DAC latch. All control inputs are level triggered. Data can be latched or transferred directly to the DAC. CS and WR control the input latch and LD_ transfers information from the input latch to the DAC latch. The input latch is transparent when CS and WR are low, and 8 Table 1. MAX547 DAC Addressing A2 A1 A0 FUNCTION 0 0 0 DAC A input latch 0 0 1 DAC B input latch 0 1 0 DAC C input latch 0 1 1 DAC D input latch 1 0 0 DAC E input latch 1 0 1 DAC F input latch 1 1 0 DAC G input latch 1 1 1 DAC H input latch TO INPUT LATCH OF DAC H TO INPUT LATCH OF DAC G A2 A1 TO INPUT LATCH OF DAC F TO INPUT LATCH OF DAC E TO INPUT LATCH OF DAC D A0 TO INPUT LATCH OF DAC C TO INPUT LATCH OF DAC B CS TO INPUT LATCH OF DAC A WR LDGH TO DAC LATCHES OF DAC G AND DAC H LDEF TO DAC LATCHES OF DAC E AND DAC G LDCD TO DAC LATCHES OF DAC C AND DAC D LDAB TO DAC LATCHES OF DAC C AND DAC B CLR TO ALL INPUT AND DAC LATCHES Figure 2. Input Control Logic the DAC latch is transparent when LD_ is low. The address lines (A0, A1, A2) must be valid throughout the time CS and WR are low (Figure 3). Otherwise, the data can be inadvertently written to the wrong DAC. Data is latched within the input latch when either CS or WR is high. Taking LD_ high latches data into the DAC latches. If LD_ is brought low when WR and CS are low, it must be held low for t3 or longer after WR and CS are high (Figure 3). Pulling the asynchronous CLR input low sets all DAC outputs to a nominal 0V, regardless of the state of CS, WR, and LD_. Taking CLR high latches 1000hex into all input latches and DAC latches. _______________________________________________________________________________________ Octal, 13-Bit Voltage-Output DAC with Parallel Interface –——– CLR 1 –——– LD– 0 –—– WR 0 –—– CS 0 1 1 1 1 X Both latches latched 1 X 1 Both latches latched 1 X 0 0 Input latch transparent 1 X 1 X Input latch latched 1 X X 1 Input latch latched 1 0 X X DAC latch transparent 0 X X X All input and DAC latches at 1000hex, outputs at AGND– FUNCTION Both latches transparent __________Applications Information Multiplying Operation The MAX547 can be used for multiplying applications. Its reference accepts both DC and AC signals. The voltage at each REF_ input sets the full-scale output voltage for its respective DACs. Since the reference inputs accept only positive voltages, multiplying operation is limited to two quadrants. Do not bypass the reference inputs when applying AC signals to them. Refer to the graphs in the Typical Operating Characteristics for dynamic performance of the DACs and output buffers. Digital Code and Analog Output Voltage The MAX547 uses offset binary coding. A 13-bit twoscomplement code can be converted to a 13-bit offset binary code by adding 212 = 4096. Bipolar Output Voltage Range (AGND_ = 0V) For symmetrical bipolar operation, tie AGND_ to the system ground. Table 3 shows the relationship between digital code and output voltage. The following paragraphs give a detailed explanation of this mode. t1 CS t5 t6 The DAC ladder output voltage (VDAC) is multiplied by 2 and level shifted by the reference voltage, which is internally connected to the output amplifiers (Figure 1). Since the feedback resistors are the same size, the amplifier’s output voltage is 2 times the voltage at its noninverting input, minus the reference voltage. t2 WR t9 t10 VOUT = 2(VDAC ) − REF– A0–A2 t7 where VDAC is the voltage at the amplifier’s noninverting input (DAC ladder output voltage), and REF_ is the voltage applied to the reference input of the DAC. With AGND_ connected to the system ground, the DAC ladder output voltage is: t8 D0–D12 t3 t3 LD– VDAC = D 2 n D (REF– ) = (REF– ) 213 where D is the numeric value of the DAC’s binary input code and n is the DAC’s resolution (13 bits). Replace VDAC in the equation and calculate the output voltage. D VOUT_ = 2 REF– − REF– 213 D D = REF– – 1 = REF– – 1 4096 212 ( NOTES: 1. ALL INPUT RISE AND FALL TIMES MEASURED FROM 10% TO 90% OF +5V. tr = tf = 5ns. 2. MEASUREMENT REFERENCE LEVEL IS (VINH + VINL)/2. 3. IF LD– IS ACTIVATED WHILE WR IS LOW THEN LD– MUST STAY LOW FOR t3 OR LONGER AFTER WR GOES HIGH. ) D ranges from 0 (20) to 8191 (213 - 1). 1 1LSB = REF– 4096 Figure 3. Write-Cycle Timing _______________________________________________________________________________________ 9 MAX547 Table 2. Interface Truth Table MAX547 Octal, 13-Bit Voltage-Output DAC with Parallel Interface Table 4. MAX547 Positive Unipolar Code Table Table 3. MAX547 Bipolar Code Table (AGND_ = REF _) 2 (AGND_ = 0V) INPUT OUTPUT INPUT OUTPUT 1 1111 1111 1111 4095 +REF_ ——— 4096 1 1111 1111 1111 8191 +REF_ ——— 8192 1 0000 0000 0001 1 +REF_ ——— 4096 1 0000 0000 0000 1 0000 0000 0000 0V 0 1111 1111 1111 1 -REF_ ——— 4096 0 0000 0000 0001 4095 -REF_ ——— 4096 0 0000 0000 0000 -REF_ ( ( ) ) ( ( +5V 1µF Customizing the Output Voltage Range The AGND_ inputs can be offset by any voltage within the supply rails if the voltage at the referring REF_ input is higher than the voltage at the AGND_ input. Select the reference voltage and the voltage at AGND_ so the resulting output voltages do not come within ±0.6V of the supply rails. Figure 4’s circuit shows one way to add positive offset to AGND_; make sure that the op amp used has sufficient current-sink capability to take up the remaining AGND_ current: ) ) 1µF REFAB 1µF VOUTA R1 DAC A AGNDAB VOUTB REF DAC B R2 1µF 1µF -5V Figure 4. Offsetting AGND– Positive Unipolar Output Voltage Range (AGND_ = REF_/2) For positive unipolar output operation, set AGND_ to (REF_/2). For example, if you use Figure 4’s circuit with, a 4.096V reference and offset AGND_ by 2.048V with matched resistors (R1 = R2) and an op amp, it results in a 0V to 4.0955V (nominal) unipolar output voltage, where 1LSB = 500µV. In general, the maximum current flowing out of any AGND_ pin is given by: I AGND_ = REF_ − AGND_ 5kΩ 10 I AGND_ = REF_ − AGND_ 5kΩ Another way is to digitally offset AGND_ by connecting the output of one DAC to one or more AGND_ inputs. Do not connect a DAC output to its own AGND_ input. Table 5 summarizes the relationship between the reference and AGND_ potentials and the output voltage in the different modes of operation. Power-Supply Sequencing MAX547 VSS VSS DIGITAL INPUTS NOT SHOWN. NOT ALL DACS SHOWN. ) +REF– /2 0V 0 0000 0000 0000 VDD VDD ( The sequence in which the supply voltages come up is not critical. However, we recommend that on power-up, VSS comes up first, VDD next, followed by the reference voltages. If you use other sequences, limit the current into any reference pin to 10mA. Also, make sure that VSS is never more than 300mV above ground. If there is a risk that this can occur at power-up, connect a Schottky diode between VSS and GND, as shown in Figure 5. We recommend that you not power up the logic input pins before establishing the supply voltages. If this is not possible and the digital lines can drive more than 10mA, you should place current-limiting resistors (e.g., 470Ω) in series with the logic pins. Reference Selection If you want a ±2.5V full-scale output voltage swing, you can use the MAX873 reference. It operates from a single 5V supply and is specified to drive up to 10mA. Therefore, it can drive all four reference inputs simultaneously. Because the maximum load impedance can vary from 1.25kΩ to 12.5kΩ (four reference inputs in parallel), the reference load current ranges from 2mA to 0.2mA (1.8mA maximum load step). The MAX873’s ______________________________________________________________________________________ Octal, 13-Bit Voltage-Output DAC with Parallel Interface MAX547 Table 5. Reference, AGND– and Output Relationships PARAMETER BIPOLAR OPERATION (AGND_ = 0V) Bipolar Zero Level, or Unipolar Mid-scale, (Code = 1000000000000) AGND_ (=0V) POSITIVE UNIPOLAR OPERATION (AGND_ = REF_/2) CUSTOM OPERATION ( AGND– AGND– ) REF_ = ——— 2 Differential Reference Voltage (VDR) REF– REF–/2 REF– - AGND– Negative Full-scale Output (Code = All 0s) -REF– 0V AGND– - VDR ( Positive Full-Scale Output (Code = All 1s) )( ) 4095 ——— 4096 REF_ REF_ ——— 4096 LSB Weight VOUT– as a Function of Digital Code (D, 0 to 8191) ( )( ) ( ) ( )( ) 8191 ——— 8192 ( 4095 AGND _ + ——— 4096 REF_ REF_ ——— 8192 )( ) D -1 ——— 4096 ( REF_ load regulation is specified to 20ppm/mA max over temperature, resulting in a maximum error of 36ppm (90µV). This corresponds to a maximum error caused by reference load regulation of only 0.147LSB [0.147LSB = 90µV/(5V/8192)LSB] over temperature. If you want a ±4.096V full-scale output swing (1LSB = 1mV), you can use the calibrated, low-drift, low-dropout MAX676. Operating from a 5V supply, it is fully specified to drive two REF_ inputs with less than 60.4µV error (0.0604LSB) over temperature, caused by the maximum load step. D ——— 8192 ( )( ) D -1 AGND _ + —--—4096 VDR VSS MAX547 1N5817 Reference Buffering Another way to obtain high accuracy is to buffer a reference with an op amp. When driving all reference inputs simultaneously, keep the closed-loop output impedance of the op amp below 0.03Ω to ensure an error of less than 0.1LSB. The op amp must also drive the capacitive load (typically 500pF to 1200pF). Each reference input can also be buffered separately by using the circuit in Figure 6. A reference load step caused by a digital transition only affects the DAC pair where the code transition occurs. It also allows the use of references with little drive capability. Keep the closed-loop output impedance of each op amp below 0.12Ω, to ensure an error of less than 0.1LSB. Figure 6 shows the op amp’s inverting input directly connected to the MAX547’s reference terminal. This eliminates the VDR VDR ——— 4096 REF_ VSS )( ) GND SYSTEM GND Figure 5. Optional Schottky Diode between VSS and GND influence of board lead resistance by sensing the voltage with a low-current path sense line directly at the reference input. Adding feedback resistors to individual reference buffer amplifiers enables different reference voltages to be generated from a single reference. ______________________________________________________________________________________ 11 Octal, 13-Bit Voltage-Output DAC with Parallel Interface MAX547 _Ordering Information (continued) PART TEMP. RANGE MAX547AEQH MAX547BEQH MAX547AEMH MAX547BEMH -40°C to +85°C -40°C to +85°C -40°C to +85°C -40°C to +85°C PIN-PACKAGE REFAB REFCD 44 PLCC 44 PLCC 44 Plastic FP 44 Plastic FP MAX547 REFEF + REFGH - MAX494 Figure 6. Reference Buffering Power-Supply Bypassing and Ground Management For optimum performance, use a multilayer PC board with an unbroken analog ground. For normal operation, when all AGND_ pins are at the same potential, connect the four AGND_ pins directly to the ground plane or connect them together in a “star” configuration. The center of this star point is a good location to connect the digital system ground with the analog ground. If you are using a single common reference voltage, you can connect the reference inputs together using a “star” configuration. If you are using DC reference voltages, bypass each reference input with a 0.1µF to 1µF capacitor to AGND_. 12 ______________________________________________________________________________________ INL (LSBs) ±2 ±4 ±2 ±4 Octal, 13-Bit Voltage-Output DAC with Parallel Interface VDD REFAB 9, 37 REFCD 10 3 REFEF REFGH 43 36 8 INPUT LATCH A DAC LATCH A INPUT LATCH B DAC LATCH B DAC B INPUT LATCH C DAC LATCH C DAC C INPUT LATCH D DAC LATCH D DAC D INPUT LATCH E DAC LATCH E DAC E INPUT LATCH F DAC LATCH F DAC F INPUT LATCH G DAC LATCH G DAC G INPUT LATCH H DAC LATCH H DAC H DAC A 11 7 6 2 5 D12–D0 AGNDAB VOUTB VOUTC AGNDCD VOUTD DATA BUS 41 44 40 39 35 38 CS WR VOUTA 14 15 CONTROL LOGIC 16, 18 A0–A2 VOUTE AGNDEF VOUTF VOUTG AGNDGH VOUTH MAX547 12, 13 32, 33 LDAB LDCD LDEF LDGH 1 CLR 4, 42 VSS 34 GND Pin numbers shown for PLCC package. ______________________________________________________________________________________ 13 MAX547 _________________________________________________________Functional Diagram VOUTF V SS VOUTE REFEF AGNDEF CLR AGNDCD REFCD VOUTD V SS VOUTC ____________________________________________________________Chip Topography VOUTB VOUTG VOUTA VOUTH V DD V DD REFGH REFAB AGNDAB AGNDGH 0.242" (6.147mm) LDAB GND LDCD LDGH CS LDEF WR D0 A2 D1 A1 D3 D4 D5 D6 D7 D8 D9 D10 D11 D12 D2 A0 MAX547 Octal, 13-Bit Voltage-Output DAC with Parallel Interface 0.199" (5.055mm) TRANSISTOR COUNT: 8987 SUBSTRATE CONNECTED TO VDD 14 ______________________________________________________________________________________ Octal, 13-Bit Voltage-Output DAC with Parallel Interface DIM A2 C e D1 D B1 D2 B A A1 A2 A3 B B1 C D D1 D2 D3 e INCHES MAX MIN 0.180 0.165 0.110 0.100 0.156 0.145 – 0.020 0.021 0.013 0.032 0.026 0.011 0.009 0.695 0.685 0.655 0.650 0.630 0.590 0.500 REF 0.050 REF MILLIMETERS MIN MAX 4.19 4.57 2.54 2.79 3.68 3.96 0.51 – 0.33 0.53 0.66 0.81 0.23 0.28 17.40 17.65 16.51 16.64 14.99 16.00 12.70 REF 1.27 REF 21-350A A3 D3 D1 D A1 A 44-PIN PLASTIC LEADED CHIP CARRIER PACKAGE ______________________________________________________________________________________ 15 MAX547 ________________________________________________________Package Information MAX547 Octal, 13-Bit Voltage-Output DAC with Parallel Interface 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 © 1995 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.