19-1562; Rev 0; 10/99 10-Bit Voltage-Output DAC in 8-Pin µMAX Applications Digital Offset and Gain Adjustment Features ♦ 10-Bit DAC with Configurable Output Amplifier ♦ +5V Single-Supply Operation ♦ Low Supply Current 0.28mA Normal Operation 2µA Shutdown Mode ♦ Available in 8-Pin µMAX ♦ Power-On Reset Clears DAC Output to Zero ♦ SPI/QSPI/MICROWIRE Compatible ♦ Schmitt-Trigger Digital Inputs for Direct Optocoupler Interface _________________Ordering Information PART TEMP. RANGE PIN-PACKAGE Industrial Process Control MAX5304CUA 0°C to +70°C 8 µMAX Microprocessor-Controlled Systems MAX5304EUA -40°C to +85°C 8 µMAX Portable Test Instruments Remote Industrial Control Functional Diagram VDD GND REF Pin Configuration TOP VIEW FB DAC REGISTER OUT DAC CONTROL DIN SCLK 8 VDD 7 GND DIN 3 6 REF SCLK 4 5 FB CS 2 INPUT REGISTER CS OUT 1 16-BIT SHIFT REGISTER MAX5304 MAX5304 µMAX SPI and QSPI are trademarks of Motorola, Inc. MICROWIRE is a trademark of National Semiconductor Corp. ________________________________________________________________ Maxim Integrated Products 1 For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800. For small orders, phone 1-800-835-8769. MAX5304 General Description The MAX5304 combines a low-power, voltage-output, 10-bit digital-to-analog converter (DAC) and a precision output amplifier in an 8-pin µMAX package. It operates from a single +5V supply, drawing less than 280µA of supply current. The output amplifier’s inverting input is available to the user, allowing specific gain configurations, remote sensing, and high output-current capability. This makes the MAX5304 ideal for a wide range of applications, including industrial process control. Other features include a software shutdown and power-on reset. The serial interface is SPI™/QSPI™/MICROWIRE™ compatible. The DAC has a double-buffered input, organized as an input register followed by a DAC register. A 16-bit serial word loads data into the input register. The DAC register can be updated independently or simultaneously with the input register. All logic inputs are TTL/CMOS-logic compatible and buffered with Schmitt triggers to allow direct interfacing to optocouplers. MAX5304 10-Bit Voltage-Output DAC in 8-Pin µMAX ABSOLUTE MAXIMUM RATINGS VDD to GND...............................................................-0.3V to +6V REF, OUT, FB to GND.................................-0.3V to (VDD + 0.3V) Digital Inputs to GND................................................-0.3V to +6V Continuous Current into Any Pin.......................................±20mA Continuous Power Dissipation (TA = +70°C) 8-Pin µMAX (derate 4.10mW/°C above+70°C) ..........330mW Operating Temperature Ranges MAX5304CUA ...................................................0°C to +70°C MAX5304EUA ................................................-40°C to +85°C Junction Temperature......................................................+150°C Storage Temperature Range.............................-65°C to +150°C Lead Temperature (soldering, 10s)........................... ......+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 (Circuit of Figure 8, VDD = +5V ±10%, VREF = +2.5V, RL = 5kΩ, CL = 100pF, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C. Output buffer connected in unity-gain configuration.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS ±1.0 LSB ±4 LSB STATIC PERFORMANCE—ANALOG SECTION Resolution N Differential Nonlinearity DNL Integral Nonlinearity (Note 1) INL Offset Error Offset-Error Tempco Gain Error (Note 1) 10 VOS ±0.3 TCVOS 6 GE -0.3 Gain-Error Tempco Power-Supply Rejection Ratio Bits Guaranteed monotonic ±8 ±2 1 PSRR mV ppm/°C LSB ppm/°C 4.5V ≤ VDD ≤ 5.5V 800 µV/V REFERENCE INPUT Reference Input Range VREF Reference Input Resistance RREF 0 Code dependent, minimum at code 1550 hex 18 VDD - 1.4 V 30 kΩ MULTIPLYING-MODE PERFORMANCE Reference -3dB Bandwidth VREF = 0.67Vp-p 650 kHz Reference Feedthrough Input code = all 0s, VREF = 3.6Vp-p at 1kHz -84 dB VREF = 1Vp-p at 25kHz, code = full scale 77 dB Signal-to-Noise Plus Distortion Ratio SINAD DIGITAL INPUTS Input High Voltage VIH Input Low Voltage VIL Input Leakage Current IIN Input Capacitance CIN 2 2.4 VIN = 0 or VDD V 0.001 8 _______________________________________________________________________________________ 0.8 V ±0.5 µA pF 10-Bit Voltage-Output DAC in 8-Pin µMAX (Circuit of Figure 8, VDD = +5V ±10%, VREF = +2.5V, RL = 5kΩ, CL = 100pF, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C. Output buffer connected in unity-gain configuration.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS DIGITAL INPUTS DYNAMIC PERFORMANCE Voltage Output Slew Rate SR Output Settling Time To ±1/2LSB, VSTEP = 2.5V Output Voltage Swing Rail-to-rail (Note 2) 0.6 V/µs 10 µs 0 to VDD V Current into FB 0.001 Start-Up Time 20 µs 5 nVs CS = VDD, DIN = 100kHz Digital Feedthrough ±0.1 µA POWER SUPPLIES Supply Voltage VDD Supply Current IDD Supply Current in Shutdown 4.5 (Note 3) 5.5 V 0.4 mA 4 20 µA 0.001 ±0.5 µA 0.28 (Note 3) Reference Current in Shutdown TIMING CHARACTERISTICS (Figure 6) SCLK Clock Period tCP 100 ns SCLK Pulse Width High tCH 40 ns SCLK Pulse Width Low tCL 40 ns CS Fall to SCLK Rise Setup Time tCSS 40 ns SCLK Rise to CS Rise Hold Time tCSH 0 ns tDS 40 ns DIN Setup Time DIN Hold Time tDH 0 ns SCLK Rise to CS Fall Delay tCS0 40 ns CS Rise to SCLK Rise Hold Time tCS1 40 ns CS Pulse Width High tCSW 100 ns Note 1: Guaranteed from code 3 to code 1023 in unity-gain configuration. Note 2: Accuracy is better than 1LSB for VOUT = 8mV to (VDD - 100mV), guaranteed by a power-supply rejection test at the end points. Note 3: RL = ∞, digital inputs at GND or VDD. _______________________________________________________________________________________ 3 MAX5304 ELECTRICAL CHARACTERISTICS (continued) __________________________________________Typical Operating Characteristics (VDD = +5V, RL = 5kΩ, CL = 100pF, TA = +25°C, unless otherwise noted.) REFERENCE VOLTAGE INPUT FREQUENCY RESPONSE -0.025 360 SUPPLY CURRENT (µA) RELATIVE OUTPUT (dB) 0 RL = ∞ 380 -4 0.025 INL (LSB) 400 MAX5304-02 0 MAX5304-01 0.050 SUPPLY CURRENT vs. TEMPERATURE MAX5304-03 INTEGRAL NONLINEARITY vs. REFERENCE VOLTAGE -8 -12 -16 340 320 300 280 260 240 220 -20 0.4 1.2 2.0 2.8 3.6 0 4.4 500k 1M REFERENCE VOLTAGE (V) 200 -60 3M -20 60 100 140 TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY -50 MAX5304-05 500 MAX5304-04 9 20 TEMPERATURE (°C) SUPPLY CURRENT vs. SUPPLY VOLTAGE 10 450 VREF = +2.5VDC + 1Vp-p SINE CODE = FULL SCALE -55 400 7 6 5 4 3 -60 350 THD + NOISE (dB) SUPPLY CURRENT (µA) 8 300 250 200 20 60 100 -90 4.0 140 4.4 4.8 5.2 5.6 100 10 TEMPERATURE (°C) FREQUENCY (kHz) OUTPUT FFT PLOT OUTPUT VOLTAGE vs. LOAD REFERENCE FEEDTHROUGH AT 1kHz -60 -80 2.49972 2.49968 2.49964 2.7 3.8 FREQUENCY (kHz) 4.9 6.0 2.49956 0.1k -40 -60 OUTPUT FEEDTHROUGH -80 2.49960 -100 REFERENCE INPUT SIGNAL -20 SIGNAL AMPLITUDE (dB) -40 0 MAX5304-09a/09b 2.49976 OUTPUT VOLTAGE (V) -20 2.49980 MAX5304-08 VREF = +3.6Vp-p CODE = FULL SCALE fIN = 1kHz 1.6 1 6.0 SUPPLY VOLTAGE (V) 0 0.5 -75 -80 0 -20 -70 -85 50 1 0 -60 -65 150 100 2 MAX5304-07 POWER-DOWN SUPPLY CURRENT (µA) 2.5M FREQUENCY (Hz) POWER-DOWN SUPPLY CURRENT vs. TEMPERATURE 4 2M 1.5M MAX5304-06 -0.050 SIGNAL AMPLITUDE (dB) MAX5304 10-Bit Voltage-Output DAC in 8-Pin µMAX -100 1k 10k LOAD (Ω) 100k 1M 0.5 1.6 2.7 3.8 FREQUENCY (kHz) _______________________________________________________________________________________ 4.9 6.0 10-Bit Voltage-Output DAC in 8-Pin µMAX (VDD = +5V, RL = 5kΩ, CL = 100pF, TA = +25°C, unless otherwise noted.) DIGITAL FEEDTHROUGH (fSCLK = 100kHz) MAX5304-11a MAX5304-10a MAJOR-CARRY TRANSITION CS 5V/div SCLK 2V/div OUT AC-COUPLED 100mV/div OUT AC-COUPLED 10mV/div CODE = 512 10µs/div 2µs/div CS = 5V MAX5304-12a DYNAMIC RESPONSE OUT 1V/div GND 10µs/div GAIN = +2V/V, SWITCHING FROM CODE 0 TO 1005 _______________________________________________________________________________________ 5 MAX5304 ____________________________Typical Operating Characteristics (continued) MAX5304 10-Bit Voltage-Output DAC in 8-Pin µMAX _____________________Pin Description FB PIN NAME FUNCTION 1 OUT 2 CS Chip-Select Input. Active low. 3 DIN Serial-Data Input 4 SCLK Serial-Clock Input 5 FB 6 REF Reference Voltage Input REF 7 GND Ground AGND 8 VDD Positive Power Supply DAC Output Voltage R 2R 2R R 2R OUT R 2R 2R MSB DAC Output Amplifier Feedback SHOWN FOR ALL 1s ON DAC Figure 1. Simplified DAC Circuit Diagram _______________Detailed Description The MAX5304 contains a voltage-output digital-to-analog converter (DAC) that is easily addressed using a simple 3-wire serial interface. Each IC includes a 16-bit shift register, and has a double-buffered input composed of an input register and a DAC register (see the Functional Diagram). In addition to the voltage output, the amplifier’s negative input is available to the user. The DAC is an inverted R-2R ladder network that converts a digital input (10 data bits plus 3 sub-bits) into an equivalent analog output voltage in proportion to the applied reference voltage. Figure 1 shows a simplified circuit diagram of the DAC. Reference Inputs The reference input accepts positive DC and AC signals. The voltage at the reference input sets the fullscale output voltage for the DAC. The reference input voltage range is 0V to (VDD - 1.4V). The output voltage (VOUT) is represented by a digitally programmable voltage source, as expressed in the following equation: VOUT = (VREF · NB / 1024) Gain where NB is the numeric value of the DAC’s binary input code (0 to 1023), VREF is the reference voltage, and Gain is the externally set voltage gain. The impedance at the reference input is code dependent, ranging from a low value of 18kΩ when the DAC has an input code of 1550 hex, to a high value exceeding several gigohms (leakage currents) with an input code of 0000 hex. Because the input impedance at the reference pin is code dependent, load regulation of the reference source is important. 6 In shutdown mode, the MAX5304’s REF input enters a high-impedance state with a typical input leakage current of 0.001µA. The reference input capacitance is also code dependent and typically ranges from 15pF (with an input code of all 0s) to 50pF (at full scale). The MAX873 +2.5V reference is recommended for use with the MAX5304. Output Amplifier The MAX5304’s DAC output is internally buffered by a precision amplifier with a typical slew rate of 0.6V/µs. Access to the output amplifier’s inverting input provides the user greater flexibility in output gain setting/signal conditioning (see the Applications Information section). With a full-scale transition at the MAX5304 output, the typical settling time to ±1/2LSB is 10µs when loaded with 5kΩ in parallel with 100pF (loads less than 2kΩ degrade performance). The amplifier’s output dynamic responses and settling performances are shown in the Typical Operating Characteristics. Shutdown Mode The MAX5304 features a software-programmable shutdown that reduces supply current to a typical value of 4µA. Writing 111X XXXX XXXX XXXX as the input-control word puts the device in shutdown mode (Table 1). _______________________________________________________________________________________ 10-Bit Voltage-Output DAC in 8-Pin µMAX MAX5304 SCLK SK DIN SO CS I/O MAX5304 In shutdown mode, the amplifier’s output and the reference input enter a high-impedance state. The serial interface remains active. Data in the input register is retained in shutdown, allowing the MAX5304 to recall the output state prior to entering shutdown. Exit shutdown mode by either recalling the previous configuration or updating the DAC with new data. When powering up the device or bringing it out of shutdown, allow 20µs for the outputs to stabilize. MICROWIRE PORT Serial-Interface Configurations The MAX5304’s 3-wire serial interface is compatible with MICROWIRE (Figure 2) and SPI/QSPI (Figure 3). The serial-input word consists of three control bits followed by 10+3 data bits (MSB first), as shown in Figure 4. The 3-bit control code determines the MAX5304’s response outlined in Table 1. The MAX5304’s digital inputs are double buffered. Depending on the command issued through the serial interface, the input register can be loaded without affecting the DAC register, the DAC register can be loaded directly, or the DAC register can be updated from the input register (Table 1). Figure 2. Connections for MICROWIRE +5V Serial-Interface Description The MAX5304 requires 16 bits of serial data. Table 1 lists the serial-interface programming commands. For certain commands, the 10+3 data bits are “don’t cares.” Data is sent MSB first and can be sent in two 8bit packets or one 16-bit word (CS must remain low until 16 bits are transferred). The serial data is composed of three control bits (C2, C1, C0), followed by the 10+3 data bits D9...D0, S2, S1, S0 (Figure 4). Set the sub-bits (S2, S1, S0) to zero. The 3-bit control code determines the register to be updated and the configuration when exiting shutdown. Figure 5 shows the serial-interface timing requirements. The chip-select pin (CS) must be low to enable the DAC’s serial interface. When CS is high, the interface control circuitry is disabled. CS must go low at least tCSS before the rising serial-clock (SCLK) edge to properly clock in the first bit. When CS is low, data is clocked into the internal shift register through the serialdata input pin (DIN) on SCLK’s rising edge. The maximum guaranteed clock frequency is 10MHz. Data is latched into the MAX5304 input/DAC register on CS’s rising edge. SS DIN MAX5304 MOSI SCLK SCK CS SPI/QSPI PORT I/O CPOL = 0, CPHA = 0 Figure 3. Connections for SPI/QSPI MSB ..................................................................................LSB 16 Bits of Serial Data Control Bits C2 C1 Data Bits MSB............................LSB Sub-Bits C0 D9 ...............................D0, S2, S1, S0 3 Control Bits 10+3 Data Bits Figure 4. Serial-Data Format _______________________________________________________________________________________ 7 MAX5304 10-Bit Voltage-Output DAC in 8-Pin µMAX Table 1. Serial-Interface Programming Commands 16-BIT16-BIT SERIAL SERIAL WORDWORD C2 C1 FUNCTION C0 D9.......................D0 MSB LSB S2...S0 X 0 0 10 bits of data 000 Load input register; DAC register immediately updated (also exit shutdown). X 0 1 10 bits of data 000 Load input register; DAC register unchanged. X 1 0 XXXXXXXXXX XXX Update DAC register from input register (also exit shutdown; recall previous state). 1 1 1 XXXXXXXXXX XXX Shutdown 0 1 1 XXXXXXXXXX XXX No operation (NOP) X = Don’t care CS COMMAND EXECUTED SCLK 1 DIN 8 C1 C2 C0 D9 D8 D7 D6 D5 9 D4 16 D3 D2 D1 D0 S2 S1 S0 Figure 5. Serial-Interface Timing Diagram tCSW CS tCSO tCSS tCL tCH tCP tCSH tCS1 SCLK tDS tDH DIN Figure 6. Detailed Serial-Interface Timing Diagram 8 _______________________________________________________________________________________ 10-Bit Voltage-Output DAC in 8-Pin µMAX MAX5304 DIN SCLK CS1 CS2 TO OTHER SERIAL DEVICES CS3 CS CS CS MAX5304 MAX5304 MAX5304 SCLK SCLK SCLK DIN DIN DIN Figure 7. Multiple MAX5304s Sharing Common DIN and SCLK Lines Figure 7 shows a method of connecting several MAX5304s. In this configuration, the clock and the data bus are common to all devices, and separate chipselect lines are used for each IC. Applications Information Table 2. Unipolar Output Codes MSB DAC CONTENTS LSB 11 1111 1111 (000) 1023 +VREF 1024 10 0000 0001 (000) 513 +VREF 1024 10 0000 0000 (000) 512 + VREF +VREF = 2 1024 01 1111 1111 (000) 511 +VREF 1024 00 0000 0001 (000) 1 +VREF 1024 00 0000 0000 (000) 0V Unipolar Output For a unipolar output, the output voltage and the reference input have the same polarity. Figure 8 shows the MAX5304 unipolar output circuit, which is also the typical operating circuit. Table 2 lists the unipolar output codes. Figure 9 illustrates a Rail-to-Rail® output configuration. This circuit shows the MAX5304 with the output amplifier configured for a closed-loop gain of +2V/V to provide a 0 to 5V full-scale range when a 2.5V reference is used. Bipolar Output The MAX5304 output can be configured for bipolar operation using Figure 10’s circuit according to the following equation: VOUT = VREF [(2NB / 1024) - 1] where NB is the numeric value of the DAC’s binary input code. Table 3 shows digital codes (offset binary) and corresponding output voltages for Figure 10’s circuit. Rail-to-Rail is a registered trademark of Nippon Motorola, Ltd. ANALOG OUTPUT Note: ( ) are for sub-bits. Using an AC Reference In applications where the reference has AC signal components, the MAX5304 has multiplying capability within the reference input range specifications. Figure 11 shows a technique for applying a sine-wave signal to the reference input where the AC signal is offset before being applied to REF. The reference voltage must never be more negative than GND. _______________________________________________________________________________________ 9 MAX5304 10-Bit Voltage-Output DAC in 8-Pin µMAX Table 3. Bipolar Output Codes MSB DAC CONTENTS LSB 11 1111 1111 ANALOG OUTPUT 511 +VREF 512 (000) 1 +VREF 512 10 0000 0001 (000) 10 0000 0000 (000) 01 1111 1111 (000) 1 -VREF 512 00 0000 0001 (000) 511 -VREF 512 00 0000 0000 (000) 0V The MAX5304’s total harmonic distortion plus noise (THD+N) is typically less than -77dB (full-scale code), given a 1Vp-p signal swing and input frequencies up to 25kHz. The typical -3dB frequency is 650kHz, as shown in the Typical Operating Characteristics graphs. Digitally Programmable Current Source Figure 12’s circuit places an NPN transistor (2N3904 or similar) within the op amp feedback loop to implement a digitally programmable, unidirectional current source. The output current is calculated with the following equation: IOUT = (VREF / R)(NB / 1024) where NB is the numeric value of the DAC’s binary input code, and R is the sense resistor shown in Figure 12. 512 -VREF = - VREF 512 Note: ( ) are for sub-bits. +5V +5V REF REF VDD VDD FB MAX5304 10k FB MAX5304 10k DAC OUT GND Figure 8. Unipolar Output Circuit 10 DAC OUT GND Figure 9. Unipolar Rail-to-Rail Output Circuit ______________________________________________________________________________________ 10-Bit Voltage-Output DAC in 8-Pin µMAX MAX5304 +5V R1 R2 REF +5V 26k AC REFERENCE INPUT +5V VDD MAX495 500mVp-p V+ FB 10k VDD REF VOUT DAC OUT DAC V- OUT MAX5304 GND MAX5304 GND R1 = R2 = 10kΩ ±0.1% Figure 10. Bipolar Output Circuit Figure 11. AC Reference Input Circuit Power-Supply Considerations +5V REF VDD VL MAX5304 IOUT DAC OUT 2N3904 FB GND R Figure 12. Digitally Programmable Current Source On power-up, the input and DAC registers are cleared (set to zero code). For rated MAX5304 performance, REF must be at least 1.4V below VDD. Bypass VDD with a 4.7µF capacitor in parallel with a 0.1µF capacitor to GND. Use short lead lengths, and place the bypass capacitors as close to the supply pins as possible. Grounding and Layout Considerations Digital or AC transient signals on GND can create noise at the analog output. Connect GND to the highest-quality ground available. Good PC board ground layout minimizes crosstalk between the DAC output, reference input, and digital input. Reduce crosstalk by keeping analog lines away from digital lines. Wire-wrapped boards are not recommended. ___________________Chip Information TRANSISTOR COUNT: 3053 SUBSTRATE CONNECTED TO AGND ______________________________________________________________________________________ 11 10-Bit Voltage-Output DAC in 8-Pin µMAX 8LUMAXD.EPS MAX5304 Package Information 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. 12 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 © 1999 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.