19-2036; Rev 0; 5/01 150ksps, 10-Bit, 2-Channel Single-Ended, and 1-Channel True-Differential ADCs in SOT23 Features ♦ Single-Supply Operation +3V(MAX1087/MAX1089) +5V(MAX1086/MAX1088) ♦ AutoShutdown Between Conversions ♦ Low Power 200µA at 150ksps 130µA at 100ksps 65µA at 50ksps 13µA at 10ksps 1.5µA at 1ksps 0.2µA in Shutdown ♦ True-Differential Track/Hold, 150kHz Sampling Rate ♦ Software-Configurable Unipolar/Bipolar Conversion (MAX1088/MAX1089 only) ♦ SPI, QSPI, MICROWIRE–Compatible Interface for DSPs and Processors ♦ Internal Conversion Clock ♦ 8-Pin SOT23 Package Ordering Information Applications Low Power Data Acquisition Portable Temperature Monitors Flowmeters Touch Screens TEMP. RANGE PINPACKAGE TOP MARK MAX1086EKA-T -40°C to +85°C 8 SOT23 AAEZ MAX1087EKA-T -40°C to +85°C 8 SOT23 AAEV MAX1088EKA-T -40°C to +85°C 8 SOT23 AAFB MAX1089EKA-T -40°C to +85°C 8 SOT23 AAEX PART Pin Configuration TOP VIEW VDD 1 AIN1 (AIN+) 2 AIN2 (AIN-) 3 GND 4 MAX1086 MAX1087 MAX1088 MAX1089 8 SCLK 7 DOUT 6 CNVST 5 REF SOT23-8 AutoShutdown is a trademark of Maxim Integrated Products. SPI and QSPI are trademarks of Motorola Inc. MICROWIRE is a trademark of National Semiconductor Corp. ( ) ARE FOR THE MAX1088/MAX1089 ________________________________________________________________ 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 MAX1086–MAX1089 General Description The MAX1086–MAX1089 are low-cost, micropower, serial output 10-bit analog-to-digital converters (ADCs) available in a tiny 8-pin SOT23. The MAX1086/MAX1088 operate with a single +5V supply. The MAX1087/MAX1089 operate with a single +3V supply. The devices feature a successive-approximation ADC, automatic shutdown, fast wake-up (1.4µs), and a high-speed 3-wire interface. Power consumption is only 0.5mW (VDD = +2.7V) at the maximum sampling rate of 150ksps. Autoshutdown™ (0.1µA) between conversions results in reduced power consumption at slower throughput rates. The MAX1086/MAX1087 provide 2-channel, singleended operation and accept input signals from 0 to VREF. The MAX1088/MAX1089 accept true-differential inputs ranging from 0 to VREF. Data is accessed using an external clock through the 3-wire SPI™, QSPI™, and MICROWIRE™–compatible serial interface. Excellent dynamic performance, low-power, ease of use, and small package size, make these converters ideal for portable battery-powered data acquisition applications, and for other applications that demand low power consumption and minimal space. MAX1086–MAX1089 150ksps, 10-Bit, 2-Channel Single-Ended, and 1-Channel True-Differential ADCs in SOT23 ABSOLUTE MAXIMUM RATINGS VDD to GND .............................................................-0.3V to +6V CNVST, SCLK, DOUT to GND......................-0.3V to (VDD+0.3V) REF, AIN1(AIN+), AIN2(AIN-) to GND..........-0.3V to (VDD+0.3V) Maximum Current Into Any Pin ...........................................50mA Continuous Power Dissipation (TA = +70°C) 8-Pin SOT23(derate 9.70mW/°C above TA = +70°C) ....777mW Operating Temperature Ranges.........................-40°C to +85°C Storage Temperature Range .............................-60°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 (VDD = +2.7V to +3.6V, VREF = +2.5V for MAX1087/MAX1089, or VDD = +4.75V to +5.25V, VREF = +4.096V for MAX1086/MAX1088, 0.1µF capacitor at REF, fSCLK = 8MHz (50% duty cycle), AIN- = GND for MAX1088/MAX1089. TA = TMIN to TMAX, unless otherwise noted. Typical values at TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS ±1.0 LSB ±1.0 LSB LSB DC ACCURACY (Note 1) Resolution 10 Relative Accuracy (Note 2) INL Differential Nonlinearity DNL Bits No missing codes over temperature Offset Error ±0.5 ±1.0 Gain Error (Note 3) ±1.0 ±2.0 Gain Temperature Coefficient Channel-to-Channel Offset ±0.8 ppm/°C ±0.1 LSB Channel-to-Channel Gain Matching ±0.1 LSB ±0.1 mV Input Common-Mode Rejection CMR VCM = 0V to VDD; zero scale input LSB DYNAMIC SPECIFICATIONS: (fIN (sine-wave) = 10kHz, VIN = 4.096Vp-p for MAX1086/MAX1088 or VIN = 2.5VPP for MAX1087/MAX1089, 150ksps, fSCLK = 8MHZ, AIN- = GND for MAX1088/MAX1089) Signal to Noise Plus Distortion SINAD 61 dB Total Harmonic Distortion (up to the 5th harmonic) THD -70 dB Spurious-Free Dynamic Range SFDR 70 dB 1 MHz 100 kHz Full-Power Bandwidth -3dB point Full-Linear Bandwidth SINAD>56dB CONVERSION RATE Conversion Time T/H Acquisition Time tCONV 3.7 tACQ 1.4 µs µs Aperture Delay 30 ns Aperture Jitter <50 ps Maximum Serial Clock Frequency Duty Cycle 2 fSCLK 8 30 _______________________________________________________________________________________ MHz 70 % 150ksps, 10-Bit, 2-Channel Single-Ended, and 1-Channel True-Differential ADCs in SOT23 (VDD = +2.7V to +3.6V, VREF = +2.5V for MAX1087/MAX1089, or VDD = +4.75V to +5.25V, VREF = +4.096V for MAX1086/MAX1088, 0.1µF capacitor at REF, fSCLK = 8MHz (50% duty cycle), AIN- = GND for MAX1088/MAX1089. TA = TMIN to TMAX, unless otherwise noted. Typical values at TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS ANALOG INPUT Unipolar Input Voltage Range (Note 4) Bipolar Input Leakage Current 0 VREF -VREF /2 VREF/2 ±0.01 Channel not selected or conversion stopped Input Capacitance ±1 34 V µA pF EXTERNAL REFERENCE INPUT Input Voltage Range VREF Input Current IREF VDD +50mV 1.0 VREF = +2.5V at 150ksps 16 VREF = +4.096V at 150ksps 26 45 ±0.01 ±1 Acquisition/Between conversions V 30 µA DIGITAL INPUTS/OUTPUT (SCLK, CNVST, DOUT) Input Low Voltage VIL Input High Voltage VIH Input Leakage Current CIN Output Low Voltage VOL Three-State Leakage Current Three-State Output Capacitance VOH ±0.1 15 ISINK = 2mA ISINK = 4mA IL CNVST = GND COUT CNVST = GND µA pF 0.4 V 0.8 V VDD -0.5 ISOURCE = 1.5mA V V IL Input Capacitance Output High Voltage 0.8 VDD -1 V ±10 15 µA pF POWER REQUIREMENTS Positive Supply Voltage VDD MAX1086/MAX1088 4.75 5.0 5.25 MAX1087/MAX1089 2.7 3.0 3.6 fSAMPLE =150ksps 245 350 fSAMPLE =100ksps 150 fSAMPLE =10ksps 15 fSAMPLE =1ksps 2 VDD = +3V Positive Supply Current IDD VDD = +5V Positive Supply Rejection PSR fSAMPLE =150ksps 320 fSAMPLE =100ksps 215 fSAMPLE =10ksps 22 fSAMPLE =1ksps 2.5 400 Shutdown 0.2 5 VDD = 5V ±5%; full-scale input ±0.1 1.0 VDD = +2.7V to +3.6V; full-scale input ±0.1 ±1.2 V µA mV _______________________________________________________________________________________ 3 MAX1086–MAX1089 ELECTRICAL CHARACTERISTICS (continued) MAX1086–MAX1089 150ksps, 10-Bit, 2-Channel Single-Ended, and 1-Channel True-Differential ADCs in SOT23 TIMING CHARACTERISTICS (Figures 1 and 2) (VDD = +2.7V to +3.6V, VREF = +2.5V for MAX1087/MAX1089, or VDD = +4.75V to +5.25V, VREF = +4.096V for MAX1086/MAX1088, 0.1µF capacitor at REF, fSCLK = 8MHz (50% duty cycle); AIN- = GND for MAX1088/MAX1089. TA = TMIN to TMAX, unless otherwise noted. Typical values at TA = +25°C.) PARAMETERS SYMBOL CONDITIONS MIN SCLK Pulse Width High tCH 38 SCLK Pulse Width Low tCL 38 TYP MAX UNITS ns ns SCLK Fall to DOUT Transition tDOT CLOAD = 30pF 60 SCLK Rise to DOUT Disable tDOD CLOAD = 30pF 500 ns CNVST Rise to DOUT Enable tDOE CLOAD = 30pF 80 ns CNVST Fall to MSB Valid tDOV CLOAD = 30pF 3.7 µs CNVST Pulse Width tCSW 100 30 ns ns Note 1: Unipolar input. Note 2: 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 3: Offset nulled. Note 4: The absolute input range for the analog inputs is from GND to VDD. ••• CNVST tCH tCL SCLK ••• tDOE DOUT tDOT HIGH-Z VDD 6kΩ DOUT DOUT 6kΩ CL GND a) HIGH -Z TO VOH, VOL TO VOH, AND VOH TO HIGH -Z tDOD HIGH-Z ••• Figure 1. Detailed Serial-Interface Timing Sequence CL GND a) HIGH -Z TO VOL, VOH TO VOL, AND VOL TO HIGH -Z Figure 2. Load Circuits for Enable/Disable Times 4 tCSW _______________________________________________________________________________________ 150ksps, 10-Bit, 2-Channel Single-Ended, and 1-Channel True-Differential ADCs in SOT23 INTEGRAL NONLINEARITY vs. OUTPUT CODE 0.6 1.0 0.6 0.4 0.2 0.2 0.2 -0.2 DNL (LSB) 0.4 0 0 -0.2 0 -0.2 -0.4 -0.4 -0.4 -0.6 -0.6 -0.6 -0.8 -0.8 -0.8 -1.0 200 400 600 800 1000 -1.0 0 1200 200 400 600 800 1000 1200 0 200 400 600 800 OUTPUT CODE OUTPUT CODE DIFFERENTIAL NONLINEARITY vs. OUTPUT CODE SUPPLY CURRENT vs. SAMPLING RATE SUPPLY CURRENT vs. SAMPLING RATE SUPPLY CURRENT (µA) 0.6 1000 0.4 0.2 0 -0.2 -0.4 MAX1087/MAX1089 1000 100 SUPPLY CURRENT (µA) MAX1086/MAX1088 0.8 MAX1086-9 toc05 1.0 10 1 -0.6 1000 1200 MAX1086-9 toc06 OUTPUT CODE MAX1086-9 toc04 0 MAX1087/MAX1089 0.8 0.4 -1.0 MAX1086/MAX1088 100 10 1 -0.8 0.1 0.001 -1.0 200 400 600 800 1000 1200 OUTPUT CODE 10 1.0 0.1 0.001 1000 1.0 SAMPLING RATE (ksps) SUPPLY CURRENT vs. SUPPLY VOLTAGE 10 1000 SAMPLING RATE (ksps) SHUTDOWN CURRENT vs. SUPPLY VOLTAGE 330 280 230 0.50 MAX1086-9 toc08 380 0.45 SHUTDOWN CURRENT (nA) MAX1086-9 toc07 0 SUPPLY CURRENT ( µA) DNL (LSB) MAX1086/MAX1088 0.8 INL (LSB) INL (LSB) 0.6 1.0 MAX1086-9 toc03 MAX1087/MAX1089 0.8 MAX1086-9 toc01 1.0 DIFFERENTIAL NONLINEARITY vs. OUTPUT CODE MAX1086-9 toc02 INTEGRAL NONLINEARITY vs. OUTPUT CODE 0.40 0.35 0.30 0.25 0.20 0.15 0.10 0.05 0 180 2.7 3.2 3.7 4.2 VDD (V) 4.7 5.2 2.7 3.2 3.7 4.2 4.7 5.2 VDD (V) _______________________________________________________________________________________ 5 MAX1086–MAX1089 Typical Operating Characteristics (VDD = +3.0V, VREF = +2.5V for MAX1087/MAX1089 or VDD = +5.0V, VREF = +4.096V for MAX1086/MAX1088, 0.1µF capacitor at REF, fSCLK = 8MHz, (50% Duty Cycle), AIN- = GND for MAX1088/1089, TA = +25°C, unless otherwise noted.) Typical Operating Characteristics (continued) (VDD = 3.0V, VREF = 2.5V for MAX1087/MAX1089 or VDD = 5.0V, VREF = +4.096V for MAX1086MAX1088, 0.1µF capacitor at REF, fSCLK = 8MHz, (50% Duty Cycle), AIN- = GND for MAX1088/89, TA = +25°C, unless otherwise noted.) SHUTDOWN CURRENT vs. TEMPERATURE 280 230 0.80 0.60 OFFSET ERROR (LSB) SHUTDOWN CURRENT (nA) 250 330 1.00 MAX1086-9 toc10 300 MAX1086-9 toc09 380 OFFSET ERROR vs. TEMPERATURE 200 150 100 MAX1086-9 toc11 SUPPLY CURRENT vs. TEMPERATURE SUPPLY CURRENT (µA) 0.40 0.20 0.00 -0.20 -0.40 0.60 50 -0.80 0 180 -40 -20 0 20 40 60 -1.00 -40 80 -20 0 20 40 60 80 -40 0 20 GAIN ERROR vs. TEMPERATURE 0.8 0.6 0.8 0.6 GAIN ERROR (LSB) 0.4 0.2 0 -0.2 MAX1086-9 toc13 1.0 MAX1086-9 toc12 1.0 0.4 0.2 0 -0.2 -0.4 -0.4 -0.6 -0.6 -0.8 -0.8 -1.0 -1.0 2.7 3.2 3.7 4.2 4.7 -40 5.2 -20 0 20 40 60 80 TEMPERATURE (°C) VDD (V) GAIN ERROR vs. SUPPLY VOLTAGE FFT PLOT (SINAD) 0.8 0.6 MAX1086-9 toc15 20.00 MAX1086-9 toc14 1.0 0.00 -20.00 AMPLITUDE (dB) 0.4 0.2 0 -0.2 -40.00 -60.00 -80.00 -0.4 -100.00 -0.6 -120.00 -0.8 -1.0 -140.00 2.7 3.2 3.7 4.2 VDD (V) 6 40 TEMPERATURE (°C) OFFSET ERROR vs. SUPPLY VOLTAGE OFFSET ERROR (LSB) -20 TEMPERATURE (°C) TEMPERATURE (°C) GAIN ERROR (LSB) MAX1086–MAX1089 150ksps, 10-Bit, 2-Channel Single-Ended, and 1-Channel True-Differential ADCs in SOT23 4.7 5.2 0 15 30 45 60 FREQUENCY (kHz) _______________________________________________________________________________________ 60 80 150ksps, 10-Bit, 2-Channel Single-Ended, and 1-Channel True-Differential ADCs in SOT23 NAME PIN MAX1086 MAX1087 MAX1088 MAX1089 1 VDD VDD Positive Supply Voltage. +2.7V to +3.6V (MAX1087/MAX1089); +4.75V to +5.25V (MAX1086/MAX1088). Bypass with a 0.1µF capacitor to GND. 2 AIN1 AIN+ Analog Input Channel 1 (MAX1086/MAX1087) or Positive Analog Input (MAX1088/MAX1089) 3 AIN2 AIN- Analog Input Channel 2 (MAX1086/MAX1087) or Negative Analog Input (MAX1088/MAX1089) 4 GND GND Ground 5 REF REF External Reference Voltage Input. Sets the analog voltage range. Bypass with a 0.1µF capacitor to GND. 6 CNVST CNVST Conversion Start. A rising edge powers-up the IC and places it in track mode. At the falling edge of CNVST, the device enters hold mode and begins conversion. CNVST also selects the input channel (MAX1086/MAX1087) or input polarity (MAX1088/MAX1089). 7 DOUT DOUT Serial Data Output. DOUT transitions the falling edge of SCLK. DOUT goes low at the start of a conversion and presents the MSB at the completion of a conversion. DOUT goes highimpedance once data has been fully clocked out. 8 SCLK SCLK Serial Clock Input. Clocks out data at DOUT MSB first. FUNCTION Detailed Description The MAX1086–MAX1089 analog-to-digital converters (ADCs) use a successive-approximation conversion (SAR) technique and an on-chip track-and-hold (T/H) structure to convert an analog signal into a 10-bit digital result. MAX1086–MAX1089 CNVST SCLK OSCILLATOR INPUT SHIFT REGISTER CONTROL AIN1 (AIN+) AIN2 (AIN-) T/H 10-BIT SAR ADC REF ( ) ARE FOR MAX1088/MAX1089 Figure 3. Simplified Functional Diagram DOUT The serial interface provides easy interfacing to microprocessors (µPs). Figure 3 shows the simplified internal structure for the MAX1086/MAX1087 (2–channels, single-ended) and the MAX1088/MAX1089 (1–channel, true-differential). True-Differential Analog Input Track/Hold The equivalent circuit of Figure 4 shows the MAX1086–MAX1089’s input architecture which is composed of a T/H, input multiplexer, comparator, and switched-capacitor DAC. The T/H enters its tracking mode on the rising edge of CNVST. The positive input capacitor is connected to AIN1 or AIN2 (MAX1086/ MAX1087) or AIN+ (MAX1088/MAX1089). The negative input capacitor is connected to GND (MAX1086/ MAX1087) or AIN- (MAX1088/MAX1089). The T/H enters its hold mode on the falling edge of CNVST and the difference between the sampled positive and negative input voltages is converted. The time required for the T/H to acquire an input signal is determined by how quickly its input capacitance is charged. If the input signal’s source impedance is high, the acquisition time lengthens, and CNVST must be held high for a longer period of time. The acquisition time, tACQ, is the maximum time needed for the signal to be acquired, plus the power-up time. It is calculated by the following equation: tACQ = 7 x (RS + RIN) x 24pF + tPWR _______________________________________________________________________________________ 7 MAX1086–MAX1089 Pin Description MAX1086–MAX1089 150ksps, 10-Bit, 2-Channel Single-Ended, and 1-Channel True-Differential ADCs in SOT23 REF GND AIN2 AIN1(AIN+) DOUT after 3.7µs. Data can then be clocked out using SCLK. If all 12 bits of data are not clocked out before CNVST is driven high, AIN2 will be selected for the next conversion. DAC CIN+ COMPARATOR + HOLD CINRIN- GND(AIN-) RIN+ HOLD *( ) APPLIES TO MAX1088/1089 VDD/2 HOLD TRACK Figure 4. Equivalent Input Circuit where RIN = 1.5kΩ, RS is the source impedance of the input signal, and tPWR = 1µs is the power-up time of the device. Note: tACQ is never less than 1.4µs and any source impedance below 300Ω does not significantly affect the ADC‘s AC performance. A high impedance source can be accommodated either by lengthening tACQ or by placing a 1µF capacitor between the positive and negative analog inputs. Selecting AIN1 or AIN2 (MAX1086/MAX1087) Select between the MAX1086/MAX1087’s two positive input channels using the CNVST pin. If AIN1 is desired (Figure 5a), drive CNVST high to power-up the ADC and place the T/H in track mode with AIN1 connected to the positive input capacitor. Hold CNVST high for tACQ to fully acquire the signal. Drive CNVST low to place the T/H in hold mode. The ADC will then perform a conversion and shutdown automatically. The MSB is available at DOUT after 3.7µs. Data can then be clocked out using SCLK. Be sure to clock out all 12 bits of data (the 10-bit result plus two sub-bits) before driving CNVST high for the next conversion. If all 12 bits of data are not clocked out before CNVST is driven high, AIN2 will be selected for the next conversion. If AIN2 is desired (Figure 5b), drive CNVST high for at least 30ns. Next, drive it low for at least 30ns, and then high again. This will power-up the ADC and place the T/H in track mode with AIN2 connected to the positive input capacitor. Now hold CNVST high for tACQ to fully acquire the signal. Drive CNVST low to place the T/H in hold mode. The ADC will then perform a conversion and shutdown automatically. The MSB is available at 8 Selecting Unipolar or Bipolar Conversions (MAX1088/MAX1089) Initiate true-differential conversions with the MAX1088/MAX1089’s unipolar and bipolar modes, using the CNVST pin. AIN+ and AIN- are sampled at the falling edge of CNVST. In unipolar mode, AIN+ can exceed AIN- by up to V REF . The output format is straight binary. In bipolar mode, either input can exceed the other by up to VREF/2. The output format is two’s complement. Note: In both modes, AIN+ and AIN- must not exceed VDD by more than 50mV or be lower than GND by more than 50mV. If unipolar mode is desired (Figure 5a), drive CNVST high to power-up the ADC and place the T/H in track mode with AIN+ and AIN- connected to the input capacitors. Hold CNVST high for tACQ to fully acquire the signal. Drive CNVST low to place the T/H in hold mode. The ADC will then perform a conversion and shutdown automatically. The MSB is available at DOUT after 3.7µs. Data can then be clocked out using SCLK. Be sure to clock out all 12 bits (the 10-bit result plus two sub-bits) of data before driving CNVST high for the next conversion. If all 12 bits of data are not clocked out before CNVST is driven high, bipolar mode will be selected for the next conversion. If bipolar mode is desired (Figure 5b), drive CNVST high for at least 30ns. Next, drive it low for at least 30ns and then high again. This will place the T/H in track mode with AIN+ and AIN- connected to the input capacitors. Now hold CNVST high for t ACQ to fully acquire the signal. Drive CNVST low to place the T/H in hold mode. The ADC will then perform a conversion and shutdown automatically. The MSB is available at DOUT after 3.7µs. Data can then be clocked out using SCLK. If all 12 bits of data are not clocked out before CNVST is driven high, bipolar mode will be selected for the next conversion. Input Bandwidth The ADCs input tracking circuitry has a 1MHz 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 high frequency signals being aliased into the frequency band of interest, anti-alias filtering is recommended. _______________________________________________________________________________________ 150ksps, 10-Bit, 2-Channel Single-Ended, and 1-Channel True-Differential ADCs in SOT23 MAX1086–MAX1089 tCONV tACQ CNVST 1 SCLK B9 MSB DOUT HIGH-Z 4 B8 B7 B6 8 B5 B4 B3 B2 12 B1 B0 LSB S1 S0 HIGH-Z SAMPLING INSTANT Figure 5a. Single Conversion AIN1 vs. GND (MAX1086/MAX1087), unipolar mode AIN+ vs. AIN- (MAX1088/MAX1089) tCONV tACQ CNVST SCLK DOUT HIGH-Z 1 B9 MSB 4 B8 B7 B6 8 B5 B4 B3 B2 12 B1 B0 LSB S1 S0 HIGH-Z SAMPLING INSTANT Figure 5b. Single Conversion AIN2 vs. GND (MAX1086/MAX1087), bipolar mode AIN+ vs. AIN- (MAX1088/MAX1089) Analog Input Protection Internal Clock Internal protection diodes which clamp the analog input to VDD and GND allow the analog input pins to swing from GND - 0.3V to VDD + 0.3V without damage. Both inputs must not exceed VDD by more than 50mV or be lower than GND by more than 50mV for accurate conversions. If an off-channel analog input voltage exceeds the supplies, limit the input current to 2mA. The MAX1086–MAX1089 operate from an internal oscillator, which is accurate within 10% of the 4MHz specified clock rate. This results in a worse case conversion time of 3.7µs. The internal clock releases the system microprocessor from running the SAR conversion clock and allows the conversion results to be read back at the processor’s convenience, at any clock rate from 0 to 8MHz. _______________________________________________________________________________________ 9 MAX1086–MAX1089 150ksps, 10-Bit, 2-Channel Single-Ended, and 1-Channel True-Differential ADCs in SOT23 Output Data Format Figures 5a and 5b illustrate the conversion timing for the MAX1086–MAX1089. The 10-bit conversion result is output in MSB first format, followed by two sub-bits (S1 and S0). Data on DOUT transitions on the falling edge of SCLK. All 12-bits must be clocked out before CNVST transitions again. For the MAX1088/MAX1089, data is straight binary for unipolar mode and two’s complement for bipolar mode. For the MAX1086/MAX1087, data is always straight binary. Applications Information Automatic Shutdown Mode With CNVST low, the MAX1086–MAX1089 defaults to an AutoShutdown state (<0.2µA) after power-up and between conversions. After detecting a rising edge on CNVST, the part powers up, sets DOUT low and enters track mode. After detecting a falling-edge on CNVST, the device enters hold mode and begins the conversion. A maximum of 3.7µs later, the device completes conversion, enters shutdown and MSB is available at DOUT. External Reference An external reference is required for the MAX1086– MAX1089. Use a 0.1µF bypass capacitor for best performance. The reference input structure allows a voltage range of +1V to VDD + 50mV. Transfer Function Figure 6 shows the unipolar transfer function for the MAX1086–MAX1089. Figure 7 shows the bipolar transfer function for the MAX1088/MAX1089. Code transitions occur halfway between successive-integer LSB values. Connection to Standard Interfaces The MAX1086–MAX1089 feature a serial interface that is fully compatible with SPI, QSPI, and MICROWIRE. If a serial interface is available, establish the CPU’s serial interface as a master, so that the CPU generates the serial clock for the ADCs. Select a clock frequency up to 8MHz. How to Perform a Conversion 1) Use a general purpose I/O line on the CPU to hold CNVST low between conversions. 2) Drive CNVST high to acquire AIN1(MAX1086/ MAX1087) or unipolar mode (MAX1088/MAX1089). To acquire AIN2(MAX1086/MAX1087) or bipolar mode (MAX1088/MAX1089), drive CNVST low and high again. 3) 4) Hold CNVST high for 1.4µs. Drive CNVST low and wait approximately 3.7µs for conversion to complete. After 3.7µs, the MSB is available at DOUT. Activate SCLK for a minimum of 12 rising clock edges. DOUT transitions on SCLK’s falling edge 5) OUTPUT CODE MAX1088/MAX1089 OUTPUT CODE FULL-SCALE TRANSITION 11 . . . 111 MAX1086– MAX1089 011 . . . 111 FS = VREF 2 011 . . . 110 ZS = 0 11 . . . 110 11 . . . 101 000 . . . 010 000 . . . 001 000 . . . 000 FS = VREF ZS = GND V 1LSB = REF 1024 00 . . . 011 -VREF 2 V 1LSB = REF 1024 -FS = 111 . . . 111 111 . . . 110 111 . . . 101 00 . . . 010 100 . . . 001 00 . . . 001 100 . . . 000 00 . . . 000 0 1 2 3 INPUT VOLTAGE (LSB) Figure 6. Unipolar Transfer Function 10 FS FS - 3/2LSB 0 - FS INPUT VOLTAGE (LSB) *VCOM ≤ VREF / 2 *VIN = (AIN+) - (AIN-) Figure 7. Bipolar Transfer Function ______________________________________________________________________________________ +FS - 1LSB 150ksps, 10-Bit, 2-Channel Single-Ended, and 1-Channel True-Differential ADCs in SOT23 SCLK’s rising edge. The first 10 bits are the data and the next two bits are sub-bits (S1, S0). DOUT then goes high impedance (Figure 9b). SPI and MICROWIRE Interface PIC16 and SSP Module and PIC17 Interface When using SPI interface (Figure 8a) or MICROWIRE (Figure 8a and 8b), set CPOL = CPHA = 0. Two 8-bit readings are necessary to obtain the entire 10-bit result from the ADC. DOUT data transitions on the serial clock’s falling edge and is clocked into the µP on SCLK’s rising edge. The first 8-bit data stream contains the first 8-bits of DOUT starting with the MSB. The second 8-bit data stream contains the remaining two result bits (B1, B0) and two trailing sub-bits (S1, S0). DOUT then goes high impedance. QSPI Interface Using the high-speed QSPI interface (Figure 9a) with CPOL = 0 and CPHA = 0, the MAX1086–MAX1089 support a maximum fSCLK of 8MHz. One 8- to16-bit reading is necessary to obtain the entire 10-bit result from the ADC. DOUT data transitions on the serial clock’s falling edge and is clocked into the µP on The MAX1086–MAX1089 are compatible with a PIC16/PIC17 microcontroller (µC), using the synchronous serial port (SSP) module To establish SPI communication, connect the controller as shown in Figure 10a and configure the PIC16/PIC17 as system master. This is done by initializing its synchronous serial port control register (SSPCON) and synchronous serial port status register (SSPSTAT) to the bit patterns shown in Tables 1 and 2. In SPI mode, the PIC16/PIC17 µCs allow eight bits of data to be synchronously transmitted and received simultaneously. Two consecutive 8-bit readings (Figure 10b) are necessary to obtain the entire 10-bit result from the ADC. DOUT data transitions on the serial clock’s falling edge and is clocked into the µC on SCLK’s rising edge. The first 8-bit data stream contains I/O CNVST I/O CNVST SCK SCLK SK SCLK MISO DOUT SI DOUT VDD MICROWIRE SPI MAX1086– MAX1089 SS MAX1086– MAX1089 Figure 8a. SPI Connections Figure 8b. MICROWIRE Connections Table 1. Detailed SSPCON Register Content CONTROL BIT MAX1086–MAX1089 SETTINGS SYNCHRONOUS SERIAL PORT CONTROL REGISTER (SSPCON) WCOL Bit 7 X Write Collision Detection Bit SSPOV Bit 6 X Receive Overflow Detect Bit SSPEN Bit 5 1 Synchronous Serial Port Enable Bit. 0: Disables serial port and configures these pins as I/O port pins. 1: Enables serial port and configures SCK, SDO and SCI pins as serial port pins. CKP Bit 4 0 Clock Polarity Select Bit. CKP = 0 for SPI master mode selection. SSPM3 Bit 3 0 SSPM2 Bit 2 0 SSPM1 Bit 1 0 SSPM0 Bit 0 1 Synchronous Serial Port Mode Select Bit. Sets SPI master mode and selects fCLK = fOSC / 16. X = Don’t care ______________________________________________________________________________________ 11 MAX1086–MAX1089 and is available in MSB-first format. Observe the SCLK to DOUT valid timing characteristic. Clock data into the µP on SCLK’s rising-edge. MAX1086–MAX1089 150ksps, 10-Bit, 2-Channel Single-Ended, and 1-Channel True-Differential ADCs in SOT23 CNVST 1ST BYTE READ 1 2ND BYTE READ 4 12 8 16 SCLK B9 MSB DOUT B8 B7 B6 B5 B4 B3 B2 B1 B0 LSB S1 S0 HIGH-Z SAMPLING INSTANT Figure 8c. SPI/MICROWIRE Interface Timing Sequence (CPOL = CPHA = 0) the first eight data bits starting with the MSB. The second 8-bit data stream contains the remaining bits, D1 through D0, and the two sub-bits S1 and S0. Layout, Grounding, and Bypassing For best performance, use printed circuit (PC) boards. Wire-wrap configurations are not recommended since the layout should ensure proper separation of analog CS CNVST SCK SCLK MISO DOUT VDD QSPI MAX1086– MAX1089 SS and digital traces. 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 PC board ground sections with only one starpoint (Figure 11), connecting the two ground systems (analog and digital). For lowest-noise operation, ensure the ground return to the star ground’s power supply is low impedance and as short as possible. Route digital signals far away from sensitive analog and reference inputs. High-frequency noise in the power supply (VDD) may degrade the performance of the ADC’s fast comparator. Bypass VDD to the star ground with a 0.1µF capacitor, located as close as possible to the MAX1086–MAX1089s power supply pin. Minimize capacitor lead length for best supply-noise rejection. Add an attenuation resistor (5Ω) if the power supply is extremely noisy. Figure 9a. QSPI Connections Table 2. Detailed SSPSTAT Register Content CONTROL BIT MAX1086–MAX1089 SETTINGS SYNCHRONOUS SERIAL STATUS REGISTER (SSPSTAT) SMP Bit 7 0 SPI Data Input Sample Phase. Input data is sampled at the middle of the data output time. CKE Bit 6 1 SPI Clock Edge Select Bit. Data will be transmitted on the rising edge of the serial clock. D/A Bit 5 X Data Address Bit P Bit 4 X Stop Bit S Bit 3 X Start Bit R/W Bit 2 X Read/Write Bit Information UA Bit 1 X Update Address BF Bit 0 X Buffer Full Status Bit X = Don’t care 12 ______________________________________________________________________________________ 150ksps, 10-Bit, 2-Channel Single-Ended, and 1-Channel True-Differential ADCs in SOT23 1 4 16 12 8 SCLK B9 MSB DOUT B8 B7 B6 B4 B5 B3 B2 B1 B0 LSB S1 HIGH-Z S0 SAMPLING INSTANT Figure 9b. QSPI Interface Timing Sequence (CPOL = CPHA = 0) Definitions VDD VDD SCLK SCK DOUT SDI CNVST I/O 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 endpoints of the transfer function, once offset and gain errors have been nullified. The static linearity parameters for the MAX1086–MAX1089 are measured using the endpoint method. PIC16/PIC17 MAX1086– MAX1089 Differential Nonlinearity GND Differential nonlinearity (DNL) is the difference between an actual step-width and the ideal value of 1LSB. A DNL error specification of less than 1LSB guarantees no missing codes and a monotonic transfer function. GND Figure 10a. SPI Interface Connection for a PIC16/PIC17 Controller CNVST 1ST BYTE READ 1 2ND BYTE READ 4 8 12 16 SCLK DOUT B9 MSB B8 B7 B6 B5 B4 B3 B2 B1 B0 LSB S1 S0 HIGH-Z SAMPLING INSTANT Figure 10b. SPI Interface Timing with PIC16/PIC17 in Master Mode (CKE = 1, CKP = 0, SMP = 0, SSPM3 - SSPM0 = 0001) ______________________________________________________________________________________ 13 MAX1086–MAX1089 CNVST MAX1086–MAX1089 150ksps, 10-Bit, 2-Channel Single-Ended, and 1-Channel True-Differential ADCs in SOT23 Signal-to-Noise Plus Distortion Signal-to-noise plus distortion (SINAD) is the ratio of the fundamental input frequency’s RMS amplitude to RMS equivalent of all other ADC output signals. SINAD (dB) = 20 ✕ log (SignalRMS / NoiseRMS) SUPPLIES +3V OR +5V 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: R* = 5Ω 0.1µF VDD Effective Number of Bits VLOGIC = +5V/+3V GND GND ENOB = (SINAD - 1.76) / 6.02 +5V/+3V DGND Total Harmonic Distortion MAX1086– MAX1089 DIGITAL CIRCUITRY *OPTIONAL Figure 11. Power-Supply and Grounding Connections Aperture Definitions Aperture jitter (tAJ) is the sample-to-sample variation in the time between the samples. Aperture delay (tAD) is the time between the rising edge of the sampling clock and the instant when an 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 full-scale analog input (RMS value) to the RMS quantization error (residual error). The ideal, theoretical minimum analog-todigital noise is caused by quantization error only and results directly from the ADC’s resolution (N-bits): SNR = (6.02 ✕ N + 1.76)dB 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 THD = 20 × log V2 + V3 + V4 + V5 / V1 where V1 is the fundamental amplitude, and V2 through V5 are the amplitudes of the 2nd- through 5th-order harmonics. Spurious-Free Dynamic Range Spurious-free dynamic range (SFDR) is the ratio of RMS amplitude of the fundamental (maximum signal component) to the RMS value of the next largest distortion component. Chip Information TRANSISTOR COUNT: 6922 PROCESS: BiCMOS 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. 14 ______________________________________________________________________________________ 150ksps, 10-Bit, 2-Channel Single-Ended, and 1-Channel True-Differential ADCs in SOT23 SOT23, 8L.EPS 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. Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 15 © 2001 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products. MAX1086–MAX1089 Package Information