19-2466; Rev 0; 4/02 Low-Power, 14-Bit Analog-to-Digital Converters with Parallel Interface The 14-bit-wide MAX1065 is available in a 28-pin TSSOP package, and the byte-wide MAX1066 is available in a 20-pin TSSOP package. Both devices are available in either the 0°C to +70°C commercial, or the -40°C to +85°C extended temperature range. Features ♦ 14-Bit-Wide (MAX1065) and Byte-Wide (MAX1066) Parallel Interface ♦ High Speed: 165ksps Sample Rate ♦ Accurate: ±1LSB DNL (max), ±1LSB INL (max) ♦ 4.096V, 35ppm/°C Internal Reference ♦ External Reference Range 3.8V to 5.25V ♦ Single 4.75V to 5.25V Analog Supply Voltage ♦ 2.7V to 5.25V Digital Supply Voltage ♦ Low Supply Current 1.8mA (External Reference) 2.7mA (Internal Reference) 0.1mA AutoShutdown Mode (10ksps, External Reference) ♦ Small Footprint 28-Pin TSSOP Package (14-Bit Wide) 20-Pin TSSOP Package (Byte Wide) Ordering Information Applications Temperature Sensor/Monitor Cable/Harness Tester Accelerometer Measurements Digital Signal Processing Industrial Process Control I/O Boards Data-Acquisition Systems Typical Operating Circuit 5V ANALOG 5V DIGITAL 0.1µF 0.1µF DVDD AVDD µP DATA BUS D0–D13 ANALOG INPUT AIN R/C MAX1065 CS PINPACKAGE INL MAX1065ACUI 0°C to 70°C 28 TSSOP ±1 MAX1065BCUI 0°C to 70°C 28 TSSOP ±2 MAX1065CCUI 0°C to 70°C 28 TSSOP ±3 MAX1065AEUI -40°C to +85°C 28 TSSOP ±1 MAX1065BEUI -40°C to +85°C 28 TSSOP ±2 MAX1065CEUI -40°C to +85°C 28 TSSOP ±3 MAX1066ACUP 0°C to 70°C 20 TSSOP ±1 MAX1066BCUP 0°C to 70°C 20 TSSOP ±2 MAX1066CCUP 0°C to 70°C 20 TSSOP ±3 MAX1066AEUP -40°C to +85°C 20 TSSOP ±1 MAX1066BEUP -40°C to +85°C 20 TSSOP ±2 MAX1066CEUP -40°C to +85°C 20 TSSOP ±3 EOC REF RESET TEMP RANGE PART Pin Configurations appear at end of data sheet. REFADJ AGND DGND 0.1µF 1µF AutoShutdown is a registered trademark of Maxim Integrated Products, Inc. ________________________________________________________________ Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. 1 MAX1065/MAX1066 General Description The MAX1065/MAX1066 14-bit, low-power successive approximation analog-to-digital converters (ADCs) feature automatic power-down, a factory-trimmed internal clock, and a high-speed, 14-bit-wide (MAX1065) or byte-wide (MAX1066) parallel interface. The devices operate from a single 4.75V to 5.25V analog supply and a 2.7V to 5.25V digital supply. The MAX1065/MAX1066 use an internal 4.096V reference or an external reference. The MAX1065/MAX1066 consume only 1.8mA at a sampling rate of 165ksps with external reference and 2.7mA with internal reference. AutoShutdown™ reduces supply current to 0.1mA at 10ksps. The MAX1065/MAX1066 are ideal for high-performance, battery-powered, data-acquisition applications. Excellent dynamic performance and low-power consumption in a small package make the MAX1065/ MAX1066 the best choice for circuits with demanding power consumption and space requirements. MAX1065/MAX1066 Low-Power, 14-Bit Analog-to-Digital Converters with Parallel Interface ABSOLUTE MAXIMUM RATINGS AVDD to AGND .........................................................-0.3V to +6V DVDD to DGND.........................................................-0.3V to +6V AGND to DGND.....................................................-0.3V to +0.3V AIN, REF, REFADJ to AGND....................-0.3V to (AVDD + 0.3V) CS, HBEN, R/C, RESET to DGND ............................-0.3V to +6V Digital Output (D13–D0, EOC) to DGND ..................................................-0.3V to (DVDD + 0.3V) Maximum Continuous Current Into Any Pin ........................50mA Continuous Power Dissipation (TA = +70°C) 20-Pin TSSOP (derate 10.9mW/°C above +70°C) .......879mW 28-Pin TSSOP (derate 12.8mW/°C above +70°C) .....1026mW Operating Temperature Ranges MAX106_ _CU_ ...................................................0°C to +70°C MAX106_ _EU_ ................................................-40°C to +85°C Storage Temperature Range .............................-65°C to +150°C Junction Temperature ......................................................+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 (AVDD = DVDD = 5V, external reference = 4.096V, CREF = 1µF, CREFADJ = 0.1µF, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS DC ACCURACY Resolution Relative Accuracy (Note 1) Differential Nonlinearity N INL DNL 14 ±1 MAX106_B ±2 MAX106_C ±3 No missing codes over temperature ±1 RMS noise, includes quantization noise Transition Noise (Note 2) LSB LSB LSBRMS 0.32 Offset Error Gain Error Bits MAX106_A 0.2 1 mV ±0.002 ±0.02 %FSR Offset Drift 0.6 ppm/°C Gain Drift 0.2 ppm/°C 84 dB DYNAMIC PERFORMANCE (fIN(SINE-WAVE) = 1kHz, VIN = 4.096VP-P, 165ksps) Signal-to-Noise Plus Distortion SINAD 81 Signal-to-Noise Ratio SNR 82 Total Harmonic Distortion THD Spurious-Free Dynamic Range SFDR 84 -99 87 dB -86 dB 102 dB Full-Power Bandwidth -3dB point 4 MHz Full-Linear Bandwidth SINAD > 81dB 20 kHz CONVERSION RATE Sample Rate fSAMPLE 165 ksps Aperture Delay 40 ns Aperture Jitter 100 ps ANALOG INPUT Input Range VAIN Input Capacitance CAIN 2 0 VREF 40 _______________________________________________________________________________________ V pF Low-Power, 14-Bit Analog-to-Digital Converters with Parallel Interface (AVDD = DVDD = 5V, external reference = 4.096V, CREF = 1µF, CREFADJ = 0.1µF, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 4.056 4.096 4.136 V INTERNAL REFERENCE REF Output Voltage VREF REF Output Tempco TCREF ±35 ppm/°C REF Short-Circuit Current IREFSC ±10 mA Capacitive Bypass at REFADJ Capacitive Bypass at REF REFADJ Input Leakage Current CREFADJ 0.1 CREF 1 IREFADJ µF µF 20 µA EXTERNAL REFERENCE REFADJ Buffer Disable Threshold To power-down the internal reference REF Input Voltage Range REF Input Current Internal reference disabled IREF AVDD 0.4 3.8 VREF = 4.096V, fSAMPLE = 165ksps 62 AVDD 0.1 V AVDD V 120 ±0.1 Shutdown mode µA DIGITAL INPUTS/OUTPUTS (CS, R/C, EOC, D0–D13, RESET, HBEN) Input High Voltage 0.7 x DVDD VIH Input Low Voltage 0.3 x DVDD VIL Input Leakage Current Input Hysteresis IIN VIH = 0 or DVDD ±0.1 VHYST Input Capacitance CIN Output High Voltage VOH ISOURCE = 0.5mA, DVDD = 2.7V to 5.25V, AVDD = 5.25V Output Low Voltage VOL ISINK = 1.6mA, DVDD = 2.7V to 5.25V, AVDD = 5.25V Three-State Leakage Current IOZ D0–D13 Three-State Output Capacitance COZ ±1 V µA 0.1 V 15 pF DVDD 0.4 V ±0.1 0.4 V ±10 µA 15 pF POWER REQUIREMENTS Analog Supply Voltage AVDD 4.75 5.25 V Digital Supply Voltage DVDD 2.7 AVDD V Internal reference Analog Supply Current IAVDD External reference 165ksps 2.7 100ksps 2.0 10ksps 1.0 1ksps 1.0 165ksps 1.8 100ksps 1.1 10ksps 0.1 1ksps 0.01 3.2 2.3 mA _______________________________________________________________________________________ 3 MAX1065/MAX1066 ELECTRICAL CHARACTERISTICS (continued) MAX1065/MAX1066 Low-Power, 14-Bit Analog-to-Digital Converters with Parallel Interface ELECTRICAL CHARACTERISTICS (continued) (AVDD = DVDD = 5V, external reference = 4.096V, CREF = 1µF, CREFADJ = 0.1µF, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN 165ksps Digital Supply Current IDVDD D0–D13 = all zeros Full power-down Shutdown Supply Current (Note 3) Power-Supply Rejection Ratio (Note 4) ISHDN PSRR REF and REF buffer enabled (standby mode) TYP MAX 0.5 0.7 100ksps 0.3 10ksps 0.03 1ksps 0.003 UNITS mA IAVDD 0.05 5 mA IDVDD 0.5 5 µA IAVDD 1.0 1.2 mA IDVDD 0.5 5 µA AVDD = 5V, ±5%, full-scale input 68 dB TIMING CHARACTERISTICS (Figures 1 and 2) (AVDD = 4.75V to 5.25V, DVDD = 2.7V to AVDD, external reference = 4.096V, CREF = 1µF, CREFADJ = 0.1µF, CD13–D0, CEOC = 20pF, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL Acquisition Time tACQ Conversion Time tCONV CS Pulse Width High tCSH CS Pulse Width Low tCSL R/C to CS Fall Setup Time tDS R/C to CS Fall Hold Time tDH CS to Output Data Valid tDO HBEN Transition To Output Data Valid (MAX1066 only) tDO1 EOC Fall To CS Fall tDV CS Rise To EOC Rise tEOC Bus Relinquish Time (Note 5) tBR CONDITIONS MIN TYP MAX 1.1 4.7 (Note 5) (Note 5) 40 VDVDD = 4.75V to 5.25V 40 VDVDD = 2.7V to 4.74V 60 40 VDVDD = 2.7V to 5.25V 60 µs ns ns 0 VDVDD = 4.75V to 5.25V UNITS ns ns VDVDD = 4.75V to 5.25V 40 VDVDD = 2.7V to 4.74V 80 VDVDD = 4.75V to 5.25V 40 VDVDD = 2.7V to 4.74V 80 ns ns 0 ns VDVDD = 4.75V to 5.25V 40 VDVDD = 2.7V to 4.74V 80 VDVDD = 4.75V to 5.25V 40 VDVDD = 2.7V to 4.74V 80 ns ns Note 1: Relative accuracy is the deviation of the analog value at any code from its theoretical value after offset and gain errors have been removed. Note 2: Offset nulled. Note 3: Maximum specification is limited by automated test equipment. Note 4: Defined as the change in positive full scale caused by a ±5% variation in the nominal supply. Note 5: To ensure best performance, finish reading the data and wait tBR before starting a new acquisition. 4 _______________________________________________________________________________________ Low-Power, 14-Bit Analog-to-Digital Converters with Parallel Interface 0.4 1.0 INL (LSB) 0.2 1.5 0 -0.2 0.5 0 -0.5 -0.4 -1.0 -0.6 1 0.1 0.01 0.001 -1.5 -0.8 -1.0 -2.0 0 4096 8192 12288 16384 0.0001 0 4096 8192 12288 16384 1 10 IAVDD + IDVDD SUPPLY CURRENT vs. TEMPERATURE IAVDD + IDVDD SHUTDOWN CURRENT vs. TEMPERATURE INTERNAL REFERENCE vs. TEMPERATURE 1.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 0 0 20 40 60 -20 0 20 40 60 200 0 -200 -400 0.015 0.010 0.005 0 -0.005 -800 -0.015 0 -0.020 60 80 0 20 40 60 80 SINAD vs. FREQUENCY 100 90 80 70 60 50 40 30 -0.010 -600 -20 TEMPERATURE (°C) SINAD (dB) 400 TEMPERATURE (°C) -40 MAX1065/MAX1066 toc08 600 40 4.076 80 0.020 GAIN ERROR (%FSR) MAX1065/MAX1066 toc07 800 20 4.086 GAIN ERROR vs. TEMPERATURE OFFSET ERROR vs. TEMPERATURE 1000 0 4.096 TEMPERATURE (°C) TEMPERATURE (°C) -20 4.106 4.056 -40 80 4.116 MAX1065/MAX1066 toc09 -20 4.126 4.066 0.5 SAMPLE RATE = 165ksps MAX1065/MAX1066 toc06 MAX1065/MAX1066 toc05 4.0 4.136 INTERNAL REFERENCE (V) 1.5 4.5 SHUTDOWN CURRENT (µA) MAX1065/MAX1066 toc04 2.0 5.0 1000 100 CONVERSION RATE (ksps) 2.5 -40 0.1 OUTPUT CODE 3.0 -40 0.01 OUTPUT CODE 3.5 OFFSET ERROR (µV) 10 MAX1065/MAX1066 toc03 0.6 MAX1065/MAX1066 toc02 0.8 DNL (LSB) 2.0 MAX1065/MAX1066 toc01 1.0 SUPPLY CURRENT (mA) IAVDD + IDVDD SUPPLY CURRENT vs. SAMPLE RATE INL vs. OUTPUT CODE SUPPLY CURRENT (mA) DNL vs. OUTPUT CODE 20 10 SAMPLE RATE = 165ksps 0 -40 -20 0 20 40 TEMPERATURE (°C) 60 80 0.1 1 10 100 FREQUENCY (kHz) _______________________________________________________________________________________ 5 MAX1065/MAX1066 Typical Operating Characteristics (AVDD = DVDD = 5V, external reference = 4.096V, CREF = 1µF, CREFADJ = 0.1µF, TA = +25°C, unless otherwise noted.) Typical Operating Characteristics (continued) (AVDD = DVDD = 5V, external reference = 4.096V, CREF = 1µF, CREFADJ = 0.1µF, TA = +25°C, unless otherwise noted.) SPURIOUS-FREE DYNAMIC RANGE vs. FREQUENCY -30 90 80 SFDR (dB) -40 100 -50 -60 70 60 50 -70 40 -80 30 -90 20 -100 10 0.1 1 -40 -60 -80 -120 SAMPLE RATE = 165ksps 0.1 100 10 SAMPLE RATE = 165ksps -20 -100 0 -110 0 1.0 10 -140 0 100 20 40 60 80 FREQUENCY (kHz) FREQUENCY (kHz) FREQUENCY (kHz) MAX1065/MAX1066 toc12 SAMPLE RATE = 165ksps -20 MAX1065/MAX1066 toc11 -10 FFT AT 1kHz 110 MAX1065/MAX1066 toc10 0 MAGNITUDE (dB) TOTAL HARMONIC DISTORTION vs. FREQUENCY THD (dB) MAX1065/MAX1066 Low-Power, 14-Bit Analog-to-Digital Converters with Parallel Interface Pin Description PIN 6 NAME FUNCTION MAX1065 MAX1066 MAX1065 MAX1066 1 1 D6 D4/D12 Three-State Digital Data Output 2 2 D7 D5/D13 Three-State Digital Data Output. D13 is the MSB. 3 3 D8 D6/0 Three-State Digital Data Output 4 4 D9 D7/0 Three-State Digital Data Output 5 — D10 — Three-State Digital Data Output 6 — D11 — Three-State Digital Data Output 7 — D12 — Three-State Digital Data Output 8 — D13 — Three-State Digital Data Output (MSB) 9 5 R/C Read/Convert Input. Power up and put the MAX1065/MAX1066 in acquisition mode by holding R/C low during the first falling edge of CS. During the second falling edge of CS the level on R/C determines whether the reference and reference buffer power down or remain on after conversion. Set R/C high during the second falling edge of CS to power down the reference and buffer, or set R/C low to leave the reference and buffer powered up. Set R/C high during the third falling edge of CS to put valid data on the bus. 10 6 EOC End Of Conversion. EOC drives low when conversion is complete. Analog Supply Input. Bypass with a 0.1µF capacitor to AGND. 11 7 AVDD 12 8 AGND 13 9 AIN 14 10 AGND Analog Ground. Primary analog ground (star ground). Analog Input Analog Ground. Connect Pin 14 to Pin 12 (MAX1065). Connect Pin 10 to Pin 8 (MAX1066). _______________________________________________________________________________________ Low-Power, 14-Bit Analog-to-Digital Converters with Parallel Interface PIN NAME MAX1066 15 11 REFADJ Reference Buffer Output. Bypass REFADJ with a 0.1µF capacitor to AGND for internal reference mode. Connect REFADJ to AVDD to select external reference mode. 16 12 REF Reference Input/Output. Bypass REF with a 1µF capacitor to AGND for internal reference mode. External reference input when in external reference mode. 17 — RESET Reset Input. Logic high resets the device. HBEN High Byte-Enable Input. Used to multiplex the 14-bit conversion result. 1: Most significant byte available on the data bus. 0: Least significant byte available on the data bus. — MAX1065 FUNCTION MAX1065 13 MAX1066 Convert Start. The first falling edge of CS powers up the device and enables acquire mode when R/C is low. The second falling edge of CS starts conversion. The third falling edge of CS loads the result onto the bus when R/C is high. 18 14 CS 19 15 DGND Digital Ground 20 16 DVDD Digital Supply Voltage. Bypass with a 0.1µF capacitor to DGND. 21 17 N.C. D0/D8 No Connection. Do Not Connect (MAX1065). Three-State Digital Data Output (MAX1066). 22 18 N.C. D1/D9 No Connection. Do Not Connect (MAX1065). Three-State Digital Data Output (MAX1066). 23 19 D0 D2/D10 Three-State Digital Data Output 24 20 D1 D3/D11 Three-State Digital Data Output 25 — D2 — Three-State Digital Data Output 26 — D3 — Three-State Digital Data Output 27 — D4 — Three-State Digital Data Output 28 — D5 — Three-State Digital Data Output Functional Diagram REFADJ HBEN* AVDD AGND DVDD DGND 5kΩ REFERENCE OUTPUT REGISTERS 14 OR 8* 14 OR 8* D0–D13 OR D0/D8–D5/D13* REF AIN CAPACITIVE DAC AGND RESET** CLOCK CS SUCCESSIVEAPPROXIMATION REGISTER AND CONTROL LOGIC MAX1065 MAX1066 EOC R/C *BYTE WIDE (MAX1066 ONLY) **16-BIT WIDE (MAX1065 ONLY) _______________________________________________________________________________________ 7 MAX1065/MAX1066 Pin Description (continued) MAX1065/MAX1066 Low-Power, 14-Bit Analog-to-Digital Converters with Parallel Interface Detailed Description Converter Operation The MAX1065/MAX1066 use a successive-approximation (SAR) conversion technique with an inherent track-andhold (T/H) stage to convert an analog input into a 14-bit digital output. Parallel outputs provide a high-speed interface to most microprocessors (µPs). The Functional Diagram shows a simplified internal architecture of the MAX1065/MAX1066. Figure 3 shows a typical application circuit for the MAX1066. DVDD 1mA D0–D13 D0–D13 CLOAD = 20pF CLOAD = 20pF 1mA DGND DGND Analog Input The equivalent input circuit is shown in Figure 4. A switched capacitor digital-to-analog converter (DAC) provides an inherent track-and-hold function. The single-ended input is connected between AIN and AGND. Input Bandwidth The ADC’s input-tracking circuitry has a 4MHz smallsignal bandwidth, so it is possible to digitize highspeed transient events and measure periodic signals with bandwidths exceeding the ADC’s sampling rate by using undersampling techniques. To avoid aliasing of unwanted high-frequency signals into the frequency band of interest, use antialias filtering. Internal protection diodes, which clamp the analog input to AVDD and/or AGND, allow the input to swing from AGND - 0.3V to AVDD + 0.3V, without damaging the device. If the analog input exceeds 300mV beyond the supplies, limit the input current to 10mA. Track and Hold (T/H) a) HIGH-Z TO VOH, VOL TO VOH, AND VOH TO HIGH-Z b) HIGH-Z TO VOL, VOH TO VOL, AND VOL TO HIGH-Z Figure 1. Load Circuits for D0–D13 Enable Time, CS to D0–D13 Delay Time and Bus Relinquish Time tCSL In track mode, the analog signal is acquired on the internal hold capacitor. In hold mode, the T/H switches open and the capacitive DAC samples the analog input. tCSH CS tACQ REF POWERDOWN BIT R/C tDH tDS tDV tEOC EOC HI–Z tCONV D0–D13 tBR tDO HI-Z DATA VALID HBEN* tDO1 D7/D13–D0/D8* HIGH/LOW BYTE VALID tBR HIGH/LOW BYTE VALID *HBEN AND BYTE-WIDE DATA BUS AVAILABLE ON MAX1066 ONLY. Figure 2. MAX1065/MAX1066 Timing Diagram 8 _______________________________________________________________________________________ Low-Power, 14-Bit Analog-to-Digital Converters with Parallel Interface where R IN = 800Ω, R S = the input signal’s source impedance, and t ACQ is never less than 1.1µs. A source impedance less than 1kΩ does not significantly affect the ADC’s performance. To improve the input-signal bandwidth under AC conditions, drive AIN with a wideband buffer (>4MHz) that can drive the ADC’s input capacitance and settle quickly. Power-Down Modes Select standby mode or shutdown mode with the R/C bit during the second falling edge of CS (see Selecting Standby or Shutdown Mode section). The MAX1065/ MAX1066 automatically enter either standby mode, reference and buffer on, or shutdown, reference and buffer off, after each conversion depending on the status of R/C during the second falling edge of CS. 5V ANALOG 5V DIGITAL 0.1µF 0.1µF DVDD D0–D7 OR D8–D13 AVDD ANALOG INPUT AIN R/C MAX1066 CS EOC REF HIGH BYTE REFADJ HBEN LOW BYTE µP DATA BUS AGND DGND 0.1µF 1µF Internal Clock The MAX1065/MAX1066 generate an internal conversion clock. This frees the microprocessor from the burden of running the SAR conversion clock. Total conversion time after entering hold mode (second falling edge of CS) to end-of-conversion (EOC) falling is 4.7µs (max). Applications Information Starting a Conversion CS and R/C control acquisition and conversion in the MAX1065/MAX1066 (Figure 2). The first falling edge of CS powers up the device and puts it into acquisition mode if R/C is low. The convert start is ignored if R/C is high. When powering up from shutdown, the MAX1065/ MAX1066 needs at least 10ms (CREFADJ = 0.1µF, CREF = 1µF) for the internal reference to wake up and settle before starting the conversion. The ADC may wake up from shutdown to an unknown state. Put the ADC in a known state by completing one “dummy” conversion. The MAX1065/ MAX1066 will be in a known state, ready for actual data acquisition, after the completion of the dummy conversion. A dummy conversion consists of one full conversion cycle. The MAX1065 provides an alternative reset function to reset the device (see RESET section). Selecting Standby or Shutdown Mode The MAX1065/MAX1066 have a selectable standby or low-power shutdown mode. In standby mode, the ADC’s internal reference and reference buffer do not power down between conversions, eliminating the need to wait for the reference to power up before performing the next conversion. Shutdown mode powers down the reference and reference buffer after completing a conversion. Supply current is greatly reduced when in shutdown mode. The reference and reference buffer require a minimum of 10ms (CREFADJ = 0.1µF, CREF = 1µF) to power up and settle from shutdown. The state of R/C at the second falling edge of CS selects which power-down mode the MAX1065/ MAX1066 enters upon conversion completion. Holding R/C low causes the MAX1065/MAX1066 to enter standby mode. The reference and buffer are left on after the conversion completes. R/C high causes the MAX1065/MAX1066 to enter shutdown mode and shut down the reference and buffer after conversion (Figures 5 and 6). When using an external reference, set the REF powerdown bit high for lowest current operation. Figure 3. Typical Application Circuit for MAX1066 _______________________________________________________________________________________ 9 MAX1065/MAX1066 During the acquisition, the analog input (AIN) charges capacitor CDAC. The acquisition ends on the second falling edge of CS. At this instant, the T/H switches open. The retained charge on C DAC represents a sample of the input. In hold mode, the capacitive DAC adjusts during the remainder of the conversion time to restore node ZERO to zero within the limits of 14-bit resolution. At the end of the conversion, force CS low to put valid data on the bus. The time required for the T/H to acquire an input signal is a function of how quickly its input capacitance is charged. If the input signal’s source impedance is high, the acquisition time lengthens and more time must be allowed between conversions. The acquisition time (tACQ) is the maximum time the device takes to acquire the signal. Use the following formula to calculate acquisition time: tACQ = 11(RS + RIN) x 35pF MAX1065/MAX1066 Low-Power, 14-Bit Analog-to-Digital Converters with Parallel Interface Internal and External Reference REF TRACK Internal Reference The internal reference of the MAX1065/MAX1066 is internally buffered to provide 4.096V (typ) output at REF. Bypass REF to AGND and REFADJ to AGND with 1µF and 0.1µF respectively. Fine adjustments can be made to the internal reference voltage by sinking or sourcing current at REFADJ. The input impedance at REFADJ is nominally 5kΩ. The internal reference voltage is adjustable to ±1.5% with the circuit of Figure 7. CAPACITIVE DAC AIN ZERO CSWITCH 3pF HOLD CDAC = 32pF RIN 800Ω HOLD TRACK AGND AUTO-ZERO RAIL Figure 4. Equivalent Input Circuit Standby Mode While in standby mode, the supply current is reduced to less than 1mA (typ). The next falling edge of CS with R/C low causes the MAX1065/MAX1066 to exit standby mode and begin acquisition. The reference and reference buffer remain active to allow quick turn-on time. Standby mode allows significant power savings while running at the maximum sample rate. Shutdown Mode In shutdown mode, the reference and reference buffer are shut down between conversions. Shutdown mode reduces supply current to 0.5µA (typ) immediately after the conversion. The falling edge of CS with R/C low causes the reference and buffer to wake up and enter acquisition mode. To achieve 14-bit accuracy, allow 10ms (CREFADJ = 0.1µF, CREF = 1µF) for the internal reference to wake up. Increase wakeup time proportionally when using larger values of CREFADJ and CREF. ACQUISITION CONVERSION External Reference An external reference can be placed at either the input (REFADJ) or the output (REF) of the MAX1065/ MAX1066’s internal buffer amplifier. When connecting an external reference to REFADJ, the input impedance is typically 5kΩ. Using the buffered REFADJ input makes buffering the external reference unnecessary; however, the internal buffer output must be bypassed at REF with a 1µF capacitor. Connect REFADJ to AVDD to disable the internal buffer. Directly drive REF using an external reference. During conversion, the external reference must be able to drive 100µA of DC load current and have an output impedance of 10Ω or less. REFADJ’s impedance is typically 5kΩ. The DC input impedance of REF is 40kΩ minimum. For optimal performance, buffer the reference through an op amp and bypass REF with a 1µF capacitor. Consider the MAX1065/MAX1066’s equivalent input noise (80µVRMS) when choosing a reference. DATA OUT ACQUISITION CS REF POWERDOWN BIT CS R/C R/C EOC EOC REF AND BUFFER REF AND BUFFER Figure 5. Selecting Standby Mode 10 CONVERSION REF POWERDOWN BIT Figure 6. Selecting Shutdown Mode ______________________________________________________________________________________ DATA OUT Low-Power, 14-Bit Analog-to-Digital Converters with Parallel Interface 68kΩ 100kΩ 11...110 11...101 REFADJ 150kΩ FULL-SCALE TRANSITION 11...111 MAX1065 MAX1066 0.22µF FS = VREF VREF 16384 1LSB = 00...011 00...010 00...001 Figure 7. MAX1065/MAX1066 Reference Adjust Circuit 00...000 0 Reading the Conversion Result EOC is provided to flag the microprocessor when a conversion is complete. The falling edge of EOC signals that the data is valid and ready to be output to the bus. D0–D13 are the parallel outputs of the MAX1065/ MAX1066. These three-state outputs allow for direct connection to a microcontroller I/O bus. The outputs remain high-impedance during acquisition and conversion. Data is loaded onto the bus with the third falling edge of CS with R/C high after tDOns. Bringing CS high forces the output bus back to high-impedance. The MAX1065/MAX1066 then waits for the next falling edge of CS to start the next conversion cycle (Figure 2). The MAX1065 loads the conversion result onto a 14-bitwide data bus while the MAX1066 has a byte-wide output format. HBEN toggles the output between the most/least significant byte. The least significant byte is loaded onto the output bus when HBEN is low and the most significant byte is on the bus when HBEN is high (Figure 2). 1 2 3 FS INPUT VOLTAGE (LSB) FS - 3/2LSB Figure 8. MAX1065/MAX1066 Transfer Function the required output voltage change before the beginning of the acquisition time. At the beginning of acquisition, the internal sampling capacitor array connects to AIN (the amplifier output) causing some output disturbance. Ensure that the sampled voltage has settled to within the required limits before the end of the acquisition time. If the frequency of interest is low, AIN can be bypassed with a large enough capacitor to charge the internal sampling capacitor with very little ripple. However, for AC use, AIN must be driven by a wideband buffer (at least 10MHz), which must be stable with the ADC’s capacitive load (in parallel with any AIN bypass capacitor used) and also settle quickly. An example of this circuit using the MAX4434 is given in Figure 9. RESET Toggle RESET with CS high. The next falling edge of CS will begin acquisition. This reset is an alternative to the dummy conversion explained in the Starting a Conversion section. MAX1065/ MAX1066 Transfer Function Figure 8 shows the MAX1065/MAX1066 output transfer function. The output is coded in standard binary. Input Buffer Most applications require an input buffer amplifier to achieve 14-bit accuracy. If the input signal is multiplexed, the input channel should be switched immediately after acquisition, rather than near the end of or after a conversion. This allows more time for the input buffer amplifier to respond to a large step-change in input signal. The input amplifier must have a high enough slew rate to complete ANALOG INPUT 10Ω MAX4434 AIN 40pF Figure 9. MAX1065/MAX1066 Fast Settling Input Buffer ______________________________________________________________________________________ 11 MAX1065/MAX1066 OUTPUT CODE 5V MAX1065/MAX1066 Low-Power, 14-Bit Analog-to-Digital Converters with Parallel Interface Layout, Grounding, and Bypassing For best performance, use printed circuit boards. Do not run analog and digital lines parallel to each other, and do not lay out digital signal paths underneath the ADC package. Use separate analog and digital ground planes with only one point connecting the two ground systems (analog and digital) as close to the device as possible. Route digital signals far away from sensitive analog and reference inputs. If digital lines must cross analog lines, do so at right angles to minimize coupling digital noise onto the analog lines. If the analog and digital sections share the same supply, then isolate the digital and analog supply by connecting them with a low-value (10Ω) resistor or ferrite bead. The ADC is sensitive to high-frequency noise on the AVDD supply. Bypass AVDD to AGND with a 0.1µF capacitor in parallel with a 1µF to 10µF low-ESR capacitor and the smallest capacitor closest to the device. Keep capacitor leads short to minimize stray inductance. Definitions In reality, there are other noise sources besides quantization noise: thermal noise, reference noise, clock jitter, etc. SNR is computed by taking the ratio of the RMS signal to the RMS noise, which includes all spectral components minus the fundamental, the first five harmonics, and the DC offset. Signal-to-Noise Plus Distortion Signal-to-noise plus distortion (SINAD) is the ratio of the fundamental input frequency’s RMS amplitude to the RMS equivalent of all the other ADC output signals. SignalRMS SINAD(dB) = 20 × log (Noise + Distortion)RMS Effective Number of Bits Effective number of bits (ENOB) indicates the global accuracy of an ADC at a specific input frequency and sampling rate. An ideal ADC’s error consists of quantization noise only. With an input range equal to the fullscale range of the ADC, calculate the effective number of bits as follows: Integral Nonlinearity Integral nonlinearity (INL) is the deviation of the values on an actual transfer function from a straight line. This straight line can be either a best-straight-line fit or a line drawn between the end points of the transfer function, once offset and gain errors have been nullified. The static linearity parameters for the MAX1065/MAX1066 are measured using the end-point method. Differential Nonlinearity Differential nonlinearity (DNL) is the difference between an actual step width and the ideal value of 1LSB. A DNL error specification of 1LSB guarantees no missing codes and a monotonic transfer function. Aperture Jitter and Delay Aperture jitter is the sample-to-sample variation in the time between samples. Aperture delay is the time between the rising edge of the sampling clock and the instant when the actual sample is taken. Signal-to-Noise Ratio For a waveform perfectly reconstructed from digital samples, signal-to-noise ratio (SNR) is the ratio of the full-scale analog input (RMS value) to the RMS quantization error (residual error). The ideal, theoretical minimum analog-to-digital noise is caused by quantization noise error only and results directly from the ADC’s resolution (N-bits): ENOB = SINAD − 1.76 6.02 Total Harmonic Distortion Total harmonic distortion (THD) is the ratio of the RMS sum of the first five harmonics of the input signal to the fundamental itself. This is expressed as: 2 2 2 2 V2 + V3 + V4 + V5 THD = 20 × log V1 where V1 is the fundamental amplitude and V2 through V5 are the 2nd- through 5th-order harmonics. Spurious-Free Dynamic Range Spurious-free dynamic range (SFDR) is the ratio of the RMS amplitude of the fundamental (maximum signal component) to the RMS value of the next largest frequency component. Chip Information TRANSISTOR COUNT: 15,140 PROCESS: BiCMOS SNR = (6.02 x N + 1.76)dB where N = 14 bits. 12 ______________________________________________________________________________________ Low-Power, 14-Bit Analog-to-Digital Converters with Parallel Interface TOP VIEW D6 1 28 D5 D4/D12 1 20 D3/D11 D7 2 27 D4 D5/D13 2 19 D2/D10 D8 3 26 D3 D6/0 3 D9 4 25 D2 D7/0 4 D10 5 24 D1 R/C 5 23 D0 EOC 6 22 N.C. AVDD 7 14 CS 21 N.C. AGND 8 13 HBEN D11 6 MAX1065 D12 7 D13 8 R/C 9 20 DVDD AIN 9 EOC 10 19 DGND AGND 10 AVDD 11 18 CS AGND 12 17 RESET AIN 13 18 D1/D9 17 D0/D8 MAX1066 16 DVDD 15 DGND 12 REF 11 REFADJ TSSOP 16 REF 15 REFADJ AGND 14 TSSOP ______________________________________________________________________________________ 13 MAX1065/MAX1066 Pin Configurations Low-Power, 14-Bit Analog-to-Digital Converters with Parallel Interface TSSOP,NO PADS.EPS MAX1065/MAX1066 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. 14 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 © 2002 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.