19-3576; Rev 0; 5/05 8-/4-Channel, ±VREF Multirange Inputs, Serial 16-Bit ADCs The MAX1302/MAX1303 multirange, low-power, 16-bit, successive-approximation, analog-to-digital converters (ADCs) operate from a single +5V supply and achieve throughput rates up to 115ksps. A separate digital supply allows digital interfacing with 2.7V to 5.25V systems using the SPI™-/QSPI™-/MICROWIRE™-compatible serial interface. Partial power-down mode reduces the supply current to 1.3mA (typ). Full power-down mode reduces the power-supply current to 1µA (typ). The MAX1302 provides eight (single-ended) or four (true differential) analog input channels. The MAX1303 provides four (single-ended) or two (true differential) analog input channels. Each analog input channel is independently software programmable for seven single-ended input ranges (0 to +VREF/2, -VREF/2 to 0, 0 to +VREF, -VREF to 0, ±VREF/4, ±VREF/2, and ±VREF), and three differential input ranges (±VREF/2, ±VREF, ±2 x VREF). An on-chip +4.096V reference offers a small convenient ADC solution. The MAX1302/MAX1303 also accept an external reference voltage between 3.800V and 4.136V. The MAX1302 is available in a 24-pin TSSOP package and the MAX1303 is available in a 20-pin TSSOP package. Each device is specified for operation from -40°C to +85°C. Applications Industrial Control Systems Data-Acquisition Systems Features ♦ Software-Programmable Input Range for Each Channel ♦ Single-Ended Input Ranges 0 to +VREF/2, -VREF/2 to 0, 0 to +VREF, -VREF to 0, ±VREF/4, ±VREF/2, and ±VREF ♦ Differential Input Ranges ±VREF/2, ±VREF, and ±2 x VREF ♦ Eight Single-Ended or Four Differential Analog Inputs (MAX1302) ♦ Four Single-Ended or Two Differential Analog Inputs (MAX1303) ♦ ±6V Overvoltage Tolerant Inputs ♦ Internal or External Reference ♦ 115ksps Maximum Sample Rate ♦ Single +5V Power Supply ♦ 20-/24-Pin TSSOP Package Ordering Information PART TEMP RANGE PINCHANNELS PACKAGE MAX1302AEUG* -40°C to +85°C 24 TSSOP 8 MAX1302BEUG* -40°C to +85°C 24 TSSOP 8 MAX1303AEUP* -40°C to +85°C 20 TSSOP 4 MAX1303BEUP -40°C to +85°C 20 TSSOP 4 *Future product—contact factory for availability. Avionics Pin Configurations Robotics TOP VIEW AVDD1 1 24 AGND1 CH0 2 23 AGND2 CH1 3 22 AVDD2 CH2 4 CH3 5 SPI and QSPI are a trademarks of Motorola, Inc. MICROWIRE is a trademark of National Semiconductor Corp. 21 AGND3 MAX1302 20 REF CH4 6 19 REFCAP CH5 7 18 DVDD CH6 8 17 DVDDO CH7 9 16 DGND CS 10 15 DGNDO DIN 11 14 DOUT SSTRB 12 13 SCLK TSSOP Pin Configurations continued at end of data sheet. ________________________________________________________________ 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 MAX1302/MAX1303 General Description MAX1302/MAX1303 8-/4-Channel, ±VREF Multirange Inputs, Serial 16-Bit ADCs ABSOLUTE MAXIMUM RATINGS AVDD1 to AGND1 ....................................................-0.3V to +6V AVDD2 to AGND2 ....................................................-0.3V to +6V DVDD to DGND ........................................................-0.3V to +6V DVDDO to DGNDO ..................................................-0.3V to +6V DVDD to DVDDO ......................................................-0.3V to +6V DVDD, DVDDO to AVDD1 ........................................-0.3V to +6V AVDD1, DVDD, DVDDO to AVDD2 ..........................-0.3V to +6V DGND, DGNDO, AGND3, AGND2 to AGND1 ......-0.3V to +0.3V CS, SCLK, DIN, DOUT, SSTRB to DGNDO ............................................-0.3V to (DVDDO + 0.3V) CH0–CH7 to AGND1 ...................................................-6V to +6V REF, REFCAP to AGND1.......................-0.3V to (AVDD1 + 0.3V) Continuous Current (any pin) ...........................................±50mA Continuous Power Dissipation (TA = +70°C) 20-Pin TSSOP (derate 11mW/°C above +70°C) ..........879mW 24-Pin TSSOP (derate 12.2mW/°C above +70°C) .......976mW Operating Temperature Range ...........................-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 (AVDD1 = AVDD2 = DVDD = DVDDO = 5V, AGND1 = DGND = DGNDO = AGND2 = AGND3 = 0, fCLK = 3.5MHz (50% duty cycle), external clock mode, VREF = 4.096V (external reference operation), REFCAP = AVDD1, maximum single-ended bipolar input range (±VREF), CDOUT = 50pF, CSSTRB = 50pF, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX MAX130_A ±1.0 ±2 MAX130_B ±1.0 ±4 UNITS DC ACCURACY (Notes 1, 2) Resolution 16 Integral Nonlinearity INL Differential Nonlinearity DNL Transition Noise No missing codes -1 External or internal reference Single-ended inputs Offset Error Differential inputs (Note 3) Bits +2 1 Unipolar Bipolar Unipolar Bipolar LSB LSB LSBRMS 0 ±10 -1.0 ±10 0 ±20 -2.0 ±20 mV Channel-to-Channel Gain Matching Unipolar or bipolar 0.025 %FSR Channel-to-Channel Offset Error Matching Unipolar or bipolar 1.0 mV Unipolar 10 Bipolar 5 Offset Temperature Coefficient Gain Error Gain Temperature Coefficient Unipolar ±0.5 Bipolar ±0.3 Unipolar 1.5 Bipolar 1.0 Negative unipolar full scale to positive unipolar zero-scale Unipolar Endpoint Overlap ppm/°C 0 20 %FSR ppm/°C LSB DYNAMIC SPECIFICATIONS fIN(SINE-WAVE) = 5kHz, VIN = FSR - 0.05dB, fSAMPLE = 130ksps (Notes 1, 2) Differential inputs, FSR = 2 x VREF Signal-to-Noise Plus Distortion SINAD 88 Single-ended inputs, FSR = VREF / 2 85 Single-ended inputs, FSR = VREF / 4 2 90 Single-ended inputs, FSR = VREF 80 82 _______________________________________________________________________________________ dB 8-/4-Channel, ±VREF Multirange Inputs, Serial 16-Bit ADCs (AVDD1 = AVDD2 = DVDD = DVDDO = 5V, AGND1 = DGND = DGNDO = AGND2 = AGND3 = 0, fCLK = 3.5MHz (50% duty cycle), external clock mode, VREF = 4.096V (external reference operation), REFCAP = AVDD1, maximum single-ended bipolar input range (±VREF), CDOUT = 50pF, CSSTRB = 50pF, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER Signal-to-Noise Ratio SYMBOL SNR Total Harmonic Distortion (Up to the 5th Harmonic) THD Spurious-Free Dynamic Range SFDR CONDITIONS MIN TYP Differential inputs, FSR = 2 x VREF 90 Single-ended inputs, FSR = VREF 88 Single-ended inputs, FSR = VREF / 2 85 Single-ended inputs, FSR = VREF / 4 82 92 MAX UNITS dB -98 dB 99 dB Aperture Delay tAD Figure 21 15 ns Aperture Jitter tAJ Figure 21 100 ps 105 dB Channel-to-Channel Isolation CONVERSION RATE External clock mode, Figure 2 Byte-Wide Throughput Rate fSAMPLE 114 External acquisition mode, Figure 3 84 Internal clock mode, Figure 4 106 ksps ANALOG INPUTS (CH0–CH3 MAX1303, CH0–CH7 MAX1302, AGND1) Small-Signal Bandwidth All input ranges, VIN = 100mVP-P (Note 2) 1.5 MHz Full-Power Bandwidth All input ranges, VIN = 4VP-P (Note 2) 700 kHz R[2:1] = 001 -VREF / 4 R[2:1] = 010 -VREF / 2 R[2:1] = 011 Input Voltage Range (Table 6) VCH_ R[2:1] = 100 R[2:1] = 101 +VREF / 4 0 0 +VREF / 2 -VREF / 2 +VREF / 2 -VREF 0 R[2:1] = 110 0 +VREF R[2:1] = 111 -VREF +VREF -4.75 +5.50 True-Differential Analog CommonMode Voltage Range VCMDR DIF/SGL = 1 Common-Mode Rejection Ratio CMRR DIF/SGL = 1, input voltage range = ±VREF / 4 -VREF < VCH_ < +VREF 75 -1500 V V dB Input Current ICH_ +650 µA Input Capacitance CCH_ 5 pF Input Resistance RCH_ 6 kΩ _______________________________________________________________________________________ 3 MAX1302/MAX1303 ELECTRICAL CHARACTERISTICS (continued) MAX1302/MAX1303 8-/4-Channel, ±VREF Multirange Inputs, Serial 16-Bit ADCs ELECTRICAL CHARACTERISTICS (continued) (AVDD1 = AVDD2 = DVDD = DVDDO = 5V, AGND1 = DGND = DGNDO = AGND2 = AGND3 = 0, fCLK = 3.5MHz (50% duty cycle), external clock mode, VREF = 4.096V (external reference operation), REFCAP = AVDD1, maximum single-ended bipolar input range (±VREF), CDOUT = 50pF, CSSTRB = 50pF, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 4.096 4.136 V INTERNAL REFERENCE (Bypass REFCAP with 0.1µF to AGND1 and REF with 1.0µF to AGND1) Reference Output Voltage VREF Reference Temperature Coefficient TCREF Reference Short-Circuit Current IREFSC Reference Load Regulation 4.056 ±30 REF shorted to AGND1 10 REF shorted to AVDD -1 IREF = 0 to 0.5mA 0.1 ppm/°C mA 10 mV EXTERNAL REFERENCE (REFCAP = AVDD) Reference Input Voltage Range REFCAP Buffer Disable Threshold Reference Input Current Reference Input Resistance VREF 3.800 4.136 V VRCTH AVDD1 - 0.4 AVDD1 - 0.1 V IREF RREF (Note 4) VREF = +4.096V, external clock mode, external acquisition mode, internal clock mode, or partial power-down mode 90 200 VREF = +4.096V, full power-down mode ±0.1 ±10 External clock mode, external acquisition mode, internal clock mode, or partial power-down mode 20 Full power-down mode µA 45 kΩ 40 MΩ DIGITAL INPUTS (DIN, SCLK, CS) Input High Voltage VIH Input Low Voltage VIL Input Hysteresis 0.7 x DVDDO VHYST Input Leakage Current IIN Input Capacitance CIN V 0.3 x DVDDO V +10 µA 0.2 VIN = 0 to DVDDO -10 V 10 pF DIGITAL OUTPUTS (DOUT, SSTRB) DVDDO = 4.75V, ISINK = 10mA 0.4 DVDDO = 2.7V, ISINK = 5mA 0.4 Output Low Voltage VOL Output High Voltage VOH ISOURCE = 0.5mA DOUT Tri-State Leakage Current IDDO CS = DVDDO DVDDO - 0.4 -10 V V +10 µA POWER REQUIREMENTS (AVDD1 and AGND1, AVDD2 and AGND2, DVDD and DGND, DVDDO and DGNDO) Analog Supply Voltage AVDD1 4.75 5.25 V Digital Supply Voltage DVDD 4.75 5.25 V 4 _______________________________________________________________________________________ 8-/4-Channel, ±VREF Multirange Inputs, Serial 16-Bit ADCs (AVDD1 = AVDD2 = DVDD = DVDDO = 5V, AGND1 = DGND = DGNDO = AGND2 = AGND3 = 0, fCLK = 3.5MHz (50% duty cycle), external clock mode, VREF = 4.096V (external reference operation), REFCAP = AVDD1, maximum single-ended bipolar input range (±VREF), CDOUT = 50pF, CSSTRB = 50pF, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Preamplifier Supply Voltage AVDD2 4.75 5.25 V Digital I/O Supply Voltage DVDDO 2.70 5.25 V AVDD1 Supply Current IAVDD1 External clock mode, Internal reference external acquisition mode, or internal External reference clock mode 3 3.5 mA 2.5 3 DVDD Supply Current IDVDD External clock mode, external acquisition mode, or internal clock mode 0.9 2 mA AVDD2 Supply Current IAVDD2 External clock mode, external acquisition mode, or internal clock mode 17.5 25 mA DVDDO Supply Current IDVDDO External clock mode, external acquisition mode, or internal clock mode 0.2 1 mA Partial power-down mode Total Supply Current Power-Supply Rejection Ratio PSRR 1.3 mA Full power-down mode 2 µA All analog input ranges ±0.5 LSB TIMING CHARACTERISTICS (Figures 15 and 16) SCLK Period tCP SCLK High Pulse Width (Note 5) SCLK Low Pulse Width (Note 5) DIN to SCLK Setup tCH tCL External clock mode 272 62 External acquisition mode 228 62 Internal clock mode 100 83 External clock mode 109 External acquisition mode 92 Internal clock mode 40 External clock mode 109 External acquisition mode 92 Internal clock mode 40 µs ns ns tDS 40 ns DIN to SCLK Hold tDH 0 SCLK Fall to DOUT Valid tDO 40 ns CS Fall to DOUT Enable tDV 40 ns ns _______________________________________________________________________________________ 5 MAX1302/MAX1303 ELECTRICAL CHARACTERISTICS (continued) ELECTRICAL CHARACTERISTICS (continued) (AVDD1 = AVDD2 = DVDD = DVDDO = 5V, AGND1 = DGND = DGNDO = AGND2 = AGND3 = 0, fCLK = 3.5MHz (50% duty cycle), external clock mode, VREF = 4.096V (external reference operation), REFCAP = AVDD1, maximum single-ended bipolar input range (±VREF), CDOUT = 50pF, CSSTRB = 50pF, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL CS Rise to DOUT Disable CONDITIONS MIN TYP MAX tTR CS Fall to SCLK Rise Setup CS High Minimum Pulse Width SCLK Fall to CS Rise Hold UNITS 40 ns tCSS 40 ns tCSPW 40 ns 0 ns tCSH SSTRB Rise to CS Fall Setup 40 ns DOUT Rise/Fall Time CL = 50pF 10 ns SSTRB Rise/Fall Time CL = 50pF 10 ns Parameter tested at AVDD1 = AVDD2 = DVDD = DVDDO = 5V. See definitions in the Parameter Definitions section at the end of the data sheet. Guaranteed by correlation with single-ended measurements. To ensure external reference operation, VREFCAP must exceed (AVDD1 - 0.1V). To ensure internal reference operation, VREFCAP must be below (AVDD1 - 0.4V). Bypassing REFCAP with a 0.1µF or larger capacitor to AGND1 sets VREFCAP ≈ 4.096V. The transition point between internal reference mode and external reference mode lies between the REFCAP buffer disable threshold minimum and maximum values (Figures 17 and 18). Note 5: The SCLK duty cycle can vary between 40% and 60%, as long as the tCL and tCH timing requirements are met. Note 1: Note 2: Note 3: Note 4: Typical Operating Characteristics (AVDD1 = AVDD2 = DVDD = DVDDO = 5V, AGND1 = DGND = DGNDO = AGND2 = AGND3 = 0, fCLK = 3.5MHz (50% duty cycle), external clock mode, VREF = 4.096V (external reference operation), REFCAP = AVDD1, maximum single-ended bipolar input range (±VREF), CDOUT = 50pF, CSSTRB = 50pF; unless otherwise noted.) 2.55 TA = +85°C EXTERNAL CLOCK MODE 23 22 TA = +25°C 2.45 2.40 EXTERNAL CLOCK MODE 0.85 TA = +85°C 21 IAVDD2 (mA) 2.50 0.90 IDVDD (mA) EXTERNAL CLOCK MODE DIGITAL SUPPLY CURRENT vs. DIGITAL SUPPLY VOLTAGE MAX1302/03 toc02 24 MAX1302/03 toc01 2.60 PREAMPLIFIER SUPPLY CURRENT vs. PREAMPLIFIER SUPPLY VOLTAGE 20 19 TA = +25°C TA = +85°C 0.80 TA = +25°C 0.75 TA = -40°C 18 TA = -40°C MAX1302/03 toc03 ANALOG SUPPLY CURRENT vs. ANALOG SUPPLY VOLTAGE IAVDD1 (mA) MAX1302/MAX1303 8-/4-Channel, ±VREF Multirange Inputs, Serial 16-Bit ADCs 17 TA = -40°C 2.35 0.70 16 2.30 15 4.75 4.85 4.95 5.05 AVDD1 (V) 6 5.15 5.25 0.65 4.75 4.85 4.95 5.05 AVDD2 (V) 5.15 5.25 4.75 4.85 4.95 5.05 DVDD (V) _______________________________________________________________________________________ 5.15 5.25 8-/4-Channel, ±VREF Multirange Inputs, Serial 16-Bit ADCs DIGITAL I/O SUPPLY CURRENT vs. DIGITAL I/O SUPPLY VOLTAGE ANALOG SUPPLY CURRENT vs. ANALOG SUPPLY VOLTAGE 0.53 TA = +85°C TA = +85°C 0.20 PARTIAL POWER-DOWN MODE IAVDD1 (mA) IDVDDO (mA) 0.24 MAX1302/03 toc05 EXTERNAL CLOCK MODE 0.26 0.22 0.55 MAX1302/03 toc04 0.28 TA = +25°C 0.18 0.16 0.51 TA = +25°C 0.49 TA = -40°C TA = -40°C 0.14 0.47 0.12 0.10 0.45 4.75 4.85 4.95 5.05 5.15 4.75 4.85 4.95 5.05 5.15 DVDDO (V) AVDD1 (V) PREAMPLIFIER SUPPLY CURRENT vs. PREAMPLIFIER SUPPLY VOLTAGE DIGITAL SUPPLY CURRENT vs. DIGITAL SUPPLY VOLTAGE TA = +85°C PARTIAL POWER-DOWN MODE 0.134 0.16 TA = +25°C 0.14 TA = +85°C 0.132 IDVDD (mA) 0.18 0.136 5.25 MAX1302/03 toc07 PARTIAL POWER-DOWN MODE MAX1302/03 toc06 0.20 IAVDD2 (mA) 5.25 0.130 0.128 0.126 TA = -40°C TA = -40°C 0.124 0.12 TA = +25°C 0.122 0.120 0.10 4.75 4.85 4.95 5.05 AVDD2 (V) 5.15 5.25 4.75 4.85 4.95 5.05 5.15 5.25 DVDD (V) _______________________________________________________________________________________ 7 MAX1302/MAX1303 Typical Operating Characteristics (continued) (AVDD1 = AVDD2 = DVDD = DVDDO = 5V, AGND1 = DGND = DGNDO = AGND2 = AGND3 = 0, fCLK = 3.5MHz (50% duty cycle), external clock mode, VREF = 4.096V (external reference operation), REFCAP = AVDD1, maximum single-ended bipolar input range (±VREF), CDOUT = 50pF, CSSTRB = 50pF; unless otherwise noted.) Typical Operating Characteristics (continued) (AVDD1 = AVDD2 = DVDD = DVDDO = 5V, AGND1 = DGND = DGNDO = AGND2 = AGND3 = 0, fCLK = 3.5MHz (50% duty cycle), external clock mode, VREF = 4.096V (external reference operation), REFCAP = AVDD1, maximum single-ended bipolar input range (±VREF), CDOUT = 50pF, CSSTRB = 50pF; unless otherwise noted.) PREAMPLIFIER SUPPLY CURRENT vs. CONVERSION RATE ANALOG SUPPLY CURRENT vs. CONVERSION RATE MAX1302/03 toc09 EXTERNAL CLOCK MODE 2.5 25 MAX1302/03 toc08 3.0 fCLK = 7.5MHz (NOTE 6) 20 EXTERNAL CLOCK MODE 15 FULL POWER-DOWN MODE, PARTIAL POWER-DOWN MODE IAVDD2 (mA) PARTIAL POWER-DOWN MODE 1.5 1.0 FULL POWER-DOWN MODE 0.5 10 5 0 0 0 50 100 150 200 100 150 DIGITAL SUPPLY CURRENT vs. CONVERSION RATE DIGITAL I/O SUPPLY CURRENT vs. CONVERSION RATE 1.4 fCLK = 7.5MHz (NOTE 6) 0.5 EXTERNAL CLOCK MODE IDVDDO (mA) EXTERNAL CLOCK MODE, PARTIAL POWER-DOWN MODE 1.0 0.8 0.6 200 0.6 MAX1302/03 toc10 fCLK = 7.5MHz (NOTE 6) 1.2 50 CONVERSION RATE (ksps) 1.8 1.6 0 CONVERSION RATE (ksps) MAX1302/03 toc11 IAVDD1 (mA) 2.0 IDVDD (mA) MAX1302/MAX1303 8-/4-Channel, ±VREF Multirange Inputs, Serial 16-Bit ADCs 0.4 0.3 0.2 0.4 FULL POWER-DOWN MODE 0.1 FULL POWER-DOWN MODE, PARTIAL POWER-DOWN MODE 0.2 0 0 0 50 100 150 CONVERSION RATE (ksps) Note 6: 8 200 0 50 100 150 200 CONVERSION RATE (ksps) For partial power-down and full power-down modes, external clock mode was used for a burst of continuous samples. Partial power-down or full power-down modes were entered thereafter. By using this method, the conversion rate was found by averaging the number of conversions over the time starting from the first conversion to the end of the partial power-down or full power-down modes. _______________________________________________________________________________________ 8-/4-Channel, ±VREF Multirange Inputs, Serial 16-Bit ADCs EXTERNAL REFERENCE INPUT CURRENT vs. EXTERNAL REFERENCE INPUT VOLTAGE 0.14 0.04 0.02 0 -0.02 ±VREF/4 BIPOLAR 0.8 0.6 3.85 3.90 3.95 4.00 4.05 -0.4 -0.08 -0.8 ±VREF BIPOLAR -1.0 -40 -15 10 35 60 85 -40 -15 10 35 60 TEMPERATURE (°C) TEMPERATURE (°C) CHANNEL-TO-CHANNEL ISOLATION vs. INPUT FREQUENCY COMMON-MODE REJECTION RATIO vs. FREQUENCY INTEGRAL NONLINEARITY vs. DIGITAL OUTPUT CODE -20 MAX1302toc17 fSAMPLE = 115ksps ±VREF BIPOLAR RANGE -10 85 2.0 MAX1302/03 toc16 0 MAX1302/03 toc15 fSAMPLE = 115ksps ±VREF BIPOLAR RANGE CH0 TO CH2 fSAMPLE = 115ksps ±VREF BIPOLAR RANGE 1.5 1.0 -30 -60 -40 INL (LSB) CMRR (dB) -40 -80 -50 -60 -1.5 -90 -100 10 100 1000 10 100 10,000 1000 0 16,384 32,768 49,152 FREQUENCY (kHz) FREQUENCY (kHz) DIGITAL OUTPUT CODE DIFFERENTIAL NONLINEARITY vs. DIGITAL OUTPUT CODE FFT AT 5kHz SNR, SINAD, ENOB vs. ANALOG INPUT FREQUENCY 0 MAX1302toc18 2.0 fSAMPLE = 115ksps ±VREF BIPOLAR RANGE 1.5 -2.0 1 10,000 fSAMPLE = 115ksps fIN(SINE WAVE) = 5kHz ±VREF BIPOLAR RANGE -20 1.0 90 80 0 -0.5 SNR, SINAD (dB) MAGNITUDE (dB) -40 0.5 -60 -80 70 SNR 60 SINAD 50 40 ENOB 30 -100 -1.0 65,535 MAX1302/03 toc20 100 MAX1302toc19 1 0 -1.0 -80 -120 0.5 -0.5 -70 -100 DNL (LSB) 0 -0.2 EXTERNAL REFERENCE VOLTAGE (V) 0 -20 0.2 -0.6 4.15 4.10 +VREF/4 BIPOLAR RANGE 0.4 -0.06 -0.10 3.80 MAX1302toc14 MAX1302toc13 +VREF/2 BIPOLAR -0.04 0.13 0.12 ISOLATION (dB) ±VREF BIPOLAR RANGE 0.06 1.0 OFFSET ERROR (mV) 0.15 0.08 GAIN DRIFT (%) EXTERNAL REFERENCE CURRENT (mA) ALL MODES OFFSET DRIFT vs. TEMPERATURE 0.10 MAX1302/03 toc12 0.16 GAIN DRIFT vs. TEMPERATURE 20 -120 -1.5 0 -140 -2.0 0 16,384 32,768 49,152 DIGITAL OUTPUT CODE 65,535 fSAMPLE = 115ksps ±VREF BIPOLAR RANGE 10 0 10 20 30 TEMPERATURE (°C) 40 50 1 10 100 1000 FREQUENCY (kHz) _______________________________________________________________________________________ 9 MAX1302/MAX1303 Typical Operating Characteristics (continued) (AVDD1 = AVDD2 = DVDD = DVDDO = 5V, AGND1 = DGND = DGNDO = AGND2 = AGND3 = 0, fCLK = 3.5MHz (50% duty cycle), external clock mode, VREF = 4.096V (external reference operation), REFCAP = AVDD1, maximum single-ended bipolar input range (±VREF), CDOUT = 50pF, CSSTRB = 50pF; unless otherwise noted.) Typical Operating Characteristics (continued) (AVDD1 = AVDD2 = DVDD = DVDDO = 5V, AGND1 = DGND = DGNDO = AGND2 = AGND3 = 0, fCLK = 3.5MHz (50% duty cycle), external clock mode, VREF = 4.096V (external reference operation), REFCAP = AVDD1, maximum single-ended bipolar input range (±VREF), CDOUT = 50pF, CSSTRB = 50pF; unless otherwise noted.) SNR, SINAD, ENOB vs. SAMPLE RATE -SFDR, THD vs. SAMPLE RATE 16 0 SNR, SINAD 80 fIN(SINE WAVE) = 5kHz ±VREF BIPOLAR RANGE -20 14 MAX1302/03 toc22 MAX1302/03 toc21 100 12 40 10 8 20 fIN(SINE WAVE) = 5kHz ±VREF BIPOLAR RANGE 0 0.1 1 10 -80 THD -100 -SFDR 6 -120 1000 100 0.1 1 10 1000 100 SAMPLE RATE (ksps) -SFDR, THD vs. ANALOG INPUT FREQUENCY ANALOG INPUT CURRENT vs. ANALOG INPUT VOLTAGE ANALOG INPUT CURRENT (mA) -40 -60 -80 THD -SFDR MAX1302/03 toc24 1.5 MAX1302/03 toc23 fSAMPLE = 115ksps ±VREF BIPOLAR RANGE -100 -60 SAMPLE RATE (ksps) 0 -20 -40 -SFDR, THD (dB) 60 ENOB (BITS) SNR, SINAD (dB) ENOB -SFDR, THD (dB) 1.0 0.5 0 -0.5 -1.0 -1.5 -120 1 10 100 -6 1000 -4 -2 0 2 4 ANALOG INPUT VOLTAGE (V) FREQUENCY (kHz) SMALL-SIGNAL BANDWIDTH MAX1302/03 toc25 0 -5 ATTENUATION (dB) MAX1302/MAX1303 8-/4-Channel, ±VREF Multirange Inputs, Serial 16-Bit ADCs -10 -15 -20 -25 -30 1 10 100 1000 10,000 FREQUENCY (kHz) 10 ______________________________________________________________________________________ 6 8-/4-Channel, ±VREF Multirange Inputs, Serial 16-Bit ADCs -20 -30 -40 25,000 20,000 15,000 10,000 -50 5000 -60 0 1 10 100 1000 10,000 32,769 32,770 32,771 32,772 32,773 32,774 FREQUENCY (kHz) CODE NOISE HISTOGRAM (CODE CENTER) REFERENCE VOLTAGE vs. TIME MAX11302/03 toc28 MAX1302/03 toc29 65,534 SAMPLES 35,000 30,000 NUMBER OF HITS 65,534 SAMPLES 30,000 NUMBER OF HITS ATTENUATION (dB) -10 40,000 35,000 MAX1302/03 toc26 0 MAX1302/03toc27 NOISE HISTOGRAM (CODE EDGE) FULL-POWER BANDWIDTH 25,000 1V/div 20,000 15,000 10,000 0V 5000 0 32,767 32,768 32,769 32,770 CODE 32,771 32,772 32,773 4ms/div ______________________________________________________________________________________ 11 MAX1302/MAX1303 Typical Operating Characteristics (continued) (AVDD1 = AVDD2 = DVDD = DVDDO = 5V, AGND1 = DGND = DGNDO = AGND2 = AGND3 = 0, fCLK = 3.5MHz (50% duty cycle), external clock mode, VREF = 4.096V (external reference operation), REFCAP = AVDD1, maximum single-ended bipolar input range (±VREF), CDOUT = 50pF, CSSTRB = 50pF; unless otherwise noted.) MAX1302/MAX1303 8-/4-Channel, ±VREF Multirange Inputs, Serial 16-Bit ADCs Pin Description PIN MAX1302 MAX1303 12 NAME FUNCTION Analog Supply Voltage 1. Connect AVDD1 to a +4.75V to +5.25V power-supply voltage. Bypass AVDD1 to AGND1 with a 0.1µF capacitor. 1 2 AVDD1 2 3 CH0 Analog Input Channel 0 3 4 CH1 Analog Input Channel 1 4 5 CH2 Analog Input Channel 2 5 6 CH3 Analog Input Channel 3 6 — CH4 Analog Input Channel 4 7 — CH5 Analog Input Channel 5 8 — CH6 Analog Input Channel 6 9 — CH7 Analog Input Channel 7 10 7 CS Active-Low Chip-Select Input. When CS is low, data is clocked into the device from DIN on the rising edge of SCLK. With CS low, data is clocked out of DOUT on the falling edge of SCLK. When CS is high, activity on SCLK and DIN is ignored and DOUT is high impedance. 11 8 DIN Serial Data Input. When CS is low, data is clocked in on the rising edge of SCLK. When CS is high, transitions on DIN are ignored. 12 9 SSTRB Serial-Strobe Output. When using the internal clock, SSTRB rising edge transitions indicate that data is ready to be read from the device. When operating in external clock mode, SSTRB is always low. SSTRB does not tri-state, regardless of the state of CS, and therefore requires a dedicated I/O line. 13 10 SCLK Serial Clock Input. When CS is low, transitions on SCLK clock data into DIN and out of DOUT. When CS is high, transitions on SCLK are ignored. 14 11 DOUT Serial Data Output. When CS is low, data is clocked out of DOUT with each falling SCLK transition. When CS is high, DOUT is high impedance. 15 12 DGNDO 16 13 DGND Digital Ground. DGND, DGNDO, AGND3, AGND2, and AGND1 must be connected together. 17 14 DVDDO Digital I/O Supply Voltage Input. Connect DVDDO to a +2.7V to +5.25V power-supply voltage. Bypass DVDDO to DGNDO with a 0.1µF capacitor. 18 15 DVDD 19 16 20 17 Digital I/O Ground. DGND, DGNDO, AGND3, AGND2, and AGND1 must be connected together. Digital-Supply Voltage Input. Connect DVDD to a +4.75V to +5.25V power-supply voltage. Bypass DVDD to DGND with a 0.1µF capacitor. Bandgap-Voltage Bypass Node. For external reference operation, connect REFCAP to AVDD. For REFCAP internal reference operation, bypass REFCAP with a 0.01µF capacitor to AGND1 (VREFCAP ≈ 4.096V). REF Reference-Buffer Output/ADC Reference Input. For external reference operation, apply an external reference voltage from 3.800V to 4.136V to REF. For internal reference operation, bypassing REF with a 1µF capacitor to AGND1 sets VREF = 4.096V ±1%. ______________________________________________________________________________________ 8-/4-Channel, ±VREF Multirange Inputs, Serial 16-Bit ADCs PIN MAX1300 MAX1301 NAME FUNCTION 21 18 AGND3 Analog Signal Ground 3. AGND3 is the ADC negative reference potential. Connect AGND3 to AGND1. DGND, DGNDO, AGND3, AGND2, and AGND1 must be connected together. 22 19 AVDD2 Analog Supply Voltage 2. Connect AVDD2 to a +4.75V to +5.25V power-supply voltage. Bypass AVDD2 to AGND2 with a 0.1µF capacitor. 23 20 AGND2 Analog Ground 2. This ground carries approximately five times more current than AGND1. DGND, DGNDO, AGND3, AGND2, and AGND1 must be connected together. 24 1 AGND1 Analog Ground 1. DGND, DGNDO, AGND3, AGND2, and AGND1 must be connected together. 5.0V 0.1µF 5.0V 5.0V 0.1µF AVDD2 0.1µF AVDD1 DVDD CHO 4–20mA CH1 PLC CH2 ACCELERATION CH3 PRESSURE CH4 TEMPERATURE CH5 WHEATESTONE CH6 WHEATESTONE DVDDO SCLK MAX1302 MC68HCXX µC SCK CS I/O CH7 DIN MOSI REF SSTRB DOUT AGND2 AGND3 I/O MISO VSS REFCAP 0.1µF VDD 0.1µF AGND1 1µF 3.3V DGND DGNDO Figure 1. Typical Application Circuit Detailed Description The MAX1302/MAX1303 multirange, low-power, 16-bit successive-approximation ADCs operate from a single +5V supply and have a separate digital supply allowing digital interface with 2.7V to 5.25V systems. These 16-bit ADCs have internal track-and-hold (T/H) circuitry that supports single-ended and fully differential inputs. For single-ended conversions, the valid analog input voltage range spans from -VREF below ground to +VREF above ground. The maximum allowable differential input voltage spans from -2 x VREF to +2 x VREF. Data can be converted in a variety of software-programmable channel and data-acquisition configurations. Microprocessor (µP) con- trol is made easy through an SPI-/QSPI-/MICROWIREcompatible serial interface. The MAX1302 has eight single-ended analog input channels or four differential channels (see the Block Diagram at the end of the data sheet). The MAX1303 has four single-ended analog input channels or two differential channels. Each analog input channel is independently software programmable for seven single-ended input ranges (0 to +VREF/2, -VREF/2 to 0, 0 to +VREF, -VREF to 0, ±VREF/4, ±VREF/2, and ±VREF) and three differential input ranges (±VREF/2, ±VREF, and ±2 x VREF). Additionally, all analog input channels are fault tolerant to ±6V. A fault condition on an idle channel does not affect the conversion result of other channels. ______________________________________________________________________________________ 13 MAX1302/MAX1303 Pin Description (continued) MAX1302/MAX1303 8-/4-Channel, ±VREF Multirange Inputs, Serial 16-Bit ADCs Power Supplies Track-and-Hold Circuitry To maintain a low-noise environment, the MAX1302 and MAX1303 provide separate power supplies for each section of circuitry. Table 1 shows the four separate power supplies. Achieve optimal performance using separate AVDD1, AVDD2, DVDD, and DVDDO supplies. Alternatively, connect AV DD1 , AV DD2 , and DV DD together as close to the device as possible for a convenient power connection. Connect AGND1, AGND2, AGND3, DGND, and DGNDO together as close to the device as possible. Bypass each supply to the corresponding ground using a 0.1µF capacitor (Table 1). If significant low-frequency noise is present, add a 10µF capacitor in parallel with the 0.1µF bypass capacitor. The MAX1302/MAX1303 feature a switched-capacitor T/H architecture that allows the analog input signal to be stored as charge on sampling capacitors. See Figures 2, 3, and 4 for T/H timing and the sampling instants for each operating mode. The MAX1302/MAX1303 analog input circuitry buffers the input signal from the sampling capacitors, resulting in a constant analog input impedance with varying input voltage (Figure 5). Converter Operation Figure 6 shows the simplified analog input circuit. The analog inputs are ±6V fault tolerant and are protected by back-to-back diodes. The summing junction voltage, VSJ, is a function of the channel’s input common-mode voltage: Analog Input Circuitry Select differential or single-ended conversions using the associated analog input configuration byte (Table 2). The analog input signal source must be capable of driving the ADC’s 6kΩ input resistance (Figure 6). The MAX1302/MAX1303 ADCs feature a fully differential, successive-approximation register (SAR) conversion technique and an on-chip T/H block to convert voltage signals into a 16-bit digital result. Both singleended and differential configurations are supported with programmable unipolar and bipolar signal ranges. R1 R1 VSJ = × VCM × 2.375V + 1 + R1 + R2 R1 + R2 Table 1. MAX1302/MAX1303 Power Supplies and Bypassing POWER SUPPLY/GROUND SUPPLY VOLTAGE RANGE (V) TYPICAL SUPPLY CURRENT (mA) CIRCUIT SECTION BYPASSING DVDDO/DGNDO 2.7 to 5.25 0.2 Digital I/O 0.1µF to DGNDO AVDD2/AGND2 4.75 to 5.25 17.5 Analog Circuitry 0.1µF to AGND2 AVDD1/AGND1 4.75 to 5.25 3.0 Analog Circuitry 0.1µF to AGND1 DVDD/DGND 4.75 to 5.25 0.9 Digital Control Logic and Memory 0.1µF to DGND Table 2. Analog Input Configuration Byte BIT NUMBER 7 START 6 C2 5 C1 4 C0 14 NAME 3 DIF/SGL 2 R2 1 R1 0 R0 DESCRIPTION Start Bit. The first logic 1 after CS goes low defines the beginning of the analog input configuration byte. Channel-Select Bits. SEL[2:0] select the analog input channel to be configured (Tables 4 and 5). Differential or Single-Ended Configuration Bit. DIF/SGL = 0 configures the selected analog input channel for single-ended operation. DIF/SGL = 1 configures the channel for differential operation. In single-ended mode, input voltages are measured between the selected input channel and AGND1, as shown in Table 4. In differential mode, the input voltages are measured between two input channels, as shown in Table 5. Be aware that changing DIF/SGL adjusts the FSR, as shown in Table 6. Input-Range-Select Bits. R[2:0] select the input voltage range, as shown in Table 6 and Figure 7. ______________________________________________________________________________________ 8-/4-Channel, ±VREF Multirange Inputs, Serial 16-Bit ADCs MAX1302/MAX1303 CS 32 31 30 BYTE 3 29 28 27 26 25 24 23 22 BYTE 2 21 20 19 18 17 16 15 14 13 BYTE 1 12 11 9 10 8 7 6 5 4 3 2 1 SCLK BYTE 4 SSTRB DIN S C2 C1 C0 0 0 0 0 fSAMPLE ≈ fSCLK / 32 SAMPLING INSTANT tACQ ANALOG INPUT TRACK AND HOLD* DOUT HOLD TRACK HIGH IMPEDANCE HOLD B15 B14 B13 B12 B11 B10 B9 B8 B7 B6 B5 B4 B3 B2 B1 B0 HIGH IMPEDANCE *TRACK AND HOLD TIMING IS CONTROLLED BY SCLK. Figure 2. External Clock-Mode Conversion (Mode 0) As a result, the analog input impedance is relatively constant over the input voltage as shown in Figure 5. Single-ended conversions are internally referenced to AGND1 (Tables 3 and 4). In differential mode, IN+ and IN- are selected according to Tables 3 and 5. When configuring differential channels, the differential pair follows the analog configuration byte for the positive channel. For example, to configure CH2 and CH3 for a ±VREF differential conversion, set the CH2 analog configuration byte for a differential conversion with the ±VREF range (1010 1100). To initiate a conversion for the CH2 and CH3 differential pair, issue the command 1010 0000. Analog Input Bandwidth The MAX1302/MAX1303 input-tracking circuitry has a 1.5MHz small-signal bandwidth. The 1.5MHz input bandwidth makes it possible to digitize high-speed transient events. Harmonic distortion increases when digitizing signal frequencies above 15kHz as shown in the THD, SFDR vs. Analog Input Frequency plot in the Typical Operating Characteristics. Analog Input Range and Fault Tolerance Figure 7 illustrates the software-selectable singleended analog input voltage range that produces a valid digital output. Each analog input channel can be independently programmed to one of seven single-ended input ranges by setting the R[2:0] control bits with DIF/SGL = 0. ______________________________________________________________________________________ 15 MAX1302/MAX1303 8-/4-Channel, ±VREF Multirange Inputs, Serial 16-Bit ADCs CS SSTRB 32 31 30 BYTE 3 29 28 27 26 25 24 23 0 22 BYTE 2 21 20 19 0 18 0 17 C0 16 C1 15 C2 14 S 13 DIN 12 BYTE 1 11 9 10 8 7 6 5 4 3 2 1 SCLK BYTE 4 0 DOUT HIGH IMPEDANCE B15 B14 B13 B12 B11 B10 B9 B8 B7 B6 B5 B4 B3 B2 B1 B0 fSAMPLE ≈ fSCLK / 32 + fINTCLK / 17 SAMPLING INSTANT tACQ ANALOG INPUT TRACK AND HOLD* HOLD TRACK HOLD 100ns to 400ns 17 16 15 14 3 2 1 INTCLK** fINTCLK ≈ 4.5MHz *TRACK AND HOLD TIMING IS CONTROLLED BY SCLK. **INTCLK IS AN INTERNAL SIGNAL AND IS NOT ACCESSIBLE TO THE USER. Figure 3. External Acquisition-Mode Conversion (Mode 1) Figure 8 illustrates the software-selectable differential analog input voltage range that produces a valid digital output. Each analog input differential pair can be independently programmed to one of three differential input ranges by setting the R[2:0] control bits with DIF/SGL = 1. Regardless of the specified input voltage range and whether the channel is selected, each analog input is ±6V fault tolerant. The analog input fault protection is active whether the device is unpowered or powered. 16 Any voltage beyond FSR, but within the ±6V fault-tolerant range, applied to an analog input results in a fullscale output voltage for that channel. Clamping diodes with breakdown thresholds in excess of 6V protect the MAX1302/MAX1303 analog inputs during ESD and other transient events (Figure 6). The clamping diodes do not conduct during normal device operation, nor do they limit the current during such transients. When operating in an environment with the potential for high-energy voltage and/or current transients, protect the MAX1302/MAX1303 externally. ______________________________________________________________________________________ 8-/4-Channel, ±VREF Multirange Inputs, Serial 16-Bit ADCs MAX1302/MAX1303 CS SSTRB 24 23 0 22 BYTE 2 21 0 20 0 19 C0 18 C1 17 C2 16 S 15 DIN 14 BYTE 1 13 12 11 9 10 8 7 6 5 4 3 2 1 SCLK BYTE 3 0 DOUT B15 HIGH IMPEDANCE B14 B13 B12 B11 B10 B9 B8 B7 B6 B5 B4 B3 B2 B1 B0 fSAMPLE ≈ fSCLK / 24 + fINTCLK / 28 SAMPLING INSTANT tACQ ANALOG INPUT TRACK AND HOLD* TRACK HOLD HOLD 100ns to 400ns 28 27 26 25 14 13 12 11 10 3 2 1 INTCLK** fINTCLK ≈ 4.5MHz *TRACK AND HOLD TIMING IS CONTROLLED BY INTCLK, AND IS NOT ACCESSIBLE TO THE USER. **INTCLK IS AN INTERNAL SIGNAL AND IS NOT ACCESSIBLE TO THE USER. Figure 4. Internal Clock-Mode Conversion (Mode 2) MAX1302 MAX1303 ANALOG INPUT CURRENT (mA) 1.5 *RSOURCE 1.0 IN_+ ANALOG SIGNAL SOURCE 0.5 R2 R1 VSJ 0 R2 -0.5 *RSOURCE -1.0 ANALOG SIGNAL SOURCE -1.5 -6 -4 -2 0 2 4 IN_+ R1 VSJ 6 ANALOG INPUT VOLTAGE (V) *MINIMIZE RSOURCE TO AVOID GAIN ERROR AND DISTORTION. Figure 5. Analog Input Current vs. Input Voltage Figure 6. Simplified Analog Input Circuit ______________________________________________________________________________________ 17 MAX1302/MAX1303 8-/4-Channel, ±VREF Multirange Inputs, Serial 16-Bit ADCs Table 3. Input Data Word Formats DATA BIT OPERATION D7 (START) D6 D5 D4 D3 D2 D1 D0 Conversion-Start Byte (Tables 4 and 5) 1 C2 C1 C0 0 0 0 0 Analog-Input Configuration Byte (Table 2) 1 C2 C1 C0 DIF/SGL R2 R1 R0 Mode-Control Byte (Table 7) 1 M2 M1 M0 1 0 0 0 CH6 CH7 Table 4. Channel Selection in Single-Ended Mode (DIF/SGL = 0) CHANNEL-SELECT BIT CHANNEL C2 C1 C0 CH0 0 0 0 + 0 0 1 0 1 0 0 1 1 1 0 0 1 0 1 1 1 0 1 1 1 CH1 CH2 CH3 CH4 CH5 AGND1 - + + + + + + + - CH6 CH7 AGND1 + - Table 5. Channel Selection in True-Differential Mode (DIF/SGL = 1) CHANNEL-SELECT BIT CHANNEL C2 C1 C0 CH0 CH1 CH2 CH3 0 0 0 + + - 0 0 1 0 1 0 0 1 1 1 0 0 + 1 0 1 RESERVED 1 1 0 1 1 1 RESERVED - RESERVED Differential Common-Mode Range 18 CH5 RESERVED The MAX1302/MAX1303 differential common-mode range (VCMDR) must remain within -4.75V to +5.5V to obtain valid conversion results. The differential common-mode range is defined as: VCMDR = CH4 (CH _ +) + (CH _ −) 2 In addition to the common-mode input voltage limitations, each individual analog input must be limited to ±6V with respect to AGND1. The range-select bits R[2:0] in the analog input configuration bytes determine the full-scale range for the corresponding channel (Tables 2 and 6). Figures 9, 10, and 11 show the valid analog input voltage ranges for the MAX1302/MAX1303 when operating with FSR = VREF/2, FSR = VREF, and FSR = 2 x VREF, respectively. ______________________________________________________________________________________ 8-/4-Channel, ±VREF Multirange Inputs, Serial 16-Bit ADCs +3/4 VREF +3/2 VREF FSR = VREF +2 x VREF INPUT RANGE SELECTION BITS, R[2:0] EACH INPUT IS FAULT TOLERANT TO ±6V. 111 110 101 100 011 111 110 101 100 -2 x VREF 011 -VREF 010 -VREF -3/2 VREF 010 FSR = 4 x VREF -VREF/2 -3/4 VREF 001 FSR = VREF 0 FSR = 2 x VREF +VREF/2 001 -VREF/2 (CH_+) - (CH_-) (V) FSR = 2 x VREF FSR = VREF / 2 +VREF FSR = VREF -VREF/4 FSR = VREF 0 FSR = VREF / 2 +VREF/4 FSR = VREF / 2 (CH_) - AGND1 (V) +VREF/2 MAX1302/MAX1303 +VREF INPUT RANGE SELECTION BITS, R[2:0] EACH INPUT IS FAULT TOLERANT TO ±6V. Figure 7. Single-Ended Input Voltage Ranges Figure 8. Differential Input Voltage Ranges The shaded area contains the valid common-mode voltage ranges that support the entire FSR. Chip Select (CS) CS enables communication with the MAX1302/MAX1303. When CS is low, data is clocked into the device from DIN on the rising edge of SCLK and data is clocked out of DOUT on the falling edge of SCLK. When CS is high, activity on SCLK and DIN is ignored and DOUT is high impedance allowing DOUT to be shared with other peripherals. SSTRB is never high impedance and therefore cannot be shared with other peripherals. Digital Interface The MAX1302/MAX1303 feature a serial interface that is compatible with SPI/QSPI and MICROWIRE devices. DIN, DOUT, SCLK, CS, and SSTRB facilitate bidirectional communication between the MAX1302/MAX1303 and the master at SCLK rates up to 10MHz (internal clock mode, mode 2), 3.67MHz (external clock mode, mode 0), or 4.39MHz (external acquisition mode, mode 1). The master, typically a microcontroller, should use the CPOL = 0, CPHA = 0, SPI transfer format, as shown in the timing diagrams of Figures 2, 3, and 4. The digital interface is used to: • Select single-ended or true-differential input channel configurations • Select the unipolar or bipolar input range Serial Strobe Output (SSTRB) As shown in Figures 3 and 4, the SSTRB transitions high to indicate that the ADC has completed a conversion and results are ready to be read by the master. SSTRB remains low in the external clock mode (Figure 2) and consequently may be left unconnected. SSTRB is driven high or low regardless of the state of CS, therefore SSTRB cannot be shared with other peripherals. • Select the mode of operation: External clock (mode 0) External acquisition (mode 1) Internal clock (mode 2) Reset (mode 4) Partial power-down (mode 6) Full power-down (mode 7) • Initiate conversions and read results ______________________________________________________________________________________ 19 MAX1302/MAX1303 8-/4-Channel, ±VREF Multirange Inputs, Serial 16-Bit ADCs Table 6. Range-Select Bits DIF/SGL R2 R1 R0 0 0 0 0 No Range Change* MODE TRANSFER FUNCTION 0 0 0 1 Single-Ended Bipolar -VREF/4 to +VREF/4 Full-Scale Range (FSR) = VREF / 2 Figure 12 0 0 1 0 Single-Ended Unipolar -VREF/2 to 0 FSR = VREF / 2 Figure 13 0 0 1 1 Single-Ended Unipolar 0 to +VREF/2 FSR = VREF / 2 Figure 14 0 1 0 0 Single-Ended Bipolar -VREF/2 to +VREF/2 FSR = VREF Figure 12 0 1 0 1 Single-Ended Unipolar -VREF to 0 FSR = VREF Figure 13 0 1 1 0 Single-Ended Unipolar 0 to +VREF FSR = VREF Figure 14 Figure 12 — 0 1 1 1 DEFAULT SETTING Single-Ended Bipolar -VREF to +VREF FSR = 2 x VREF 1 0 0 0 No Range Change** 1 0 0 1 Differential Bipolar -VREF/2 to +VREF/2 FSR = VREF 1 0 1 0 Reserved — 1 0 1 1 Reserved — 1 1 0 0 Differential Bipolar -VREF to +VREF FSR = 2 x VREF 1 1 0 1 Reserved — 1 1 1 0 Reserved — 1 1 1 1 Differential Bipolar -2 x VREF to +2 x VREF FSR = 4 x VREF — Figure 12 Figure 12 Figure 12 *Conversion-Start Byte (see Table 3). **Mode-Control Byte (see Table 3). 20 ______________________________________________________________________________________ 6 4 4 COMMON-MODE VOLTAGE (V) 6 2 0 -2 -4 2 0 -2 -4 VREF = 4.096V VREF = 4.096V -6 -6 -8 -6 -4 -2 0 2 4 6 8 -8 -6 -4 INPUT VOLTAGE (V) Figure 9. Common-Mode Voltage vs. Input Voltage (FSR = VREF) 0 2 4 6 8 Figure 10. Common-Mode Voltage vs. Input Voltage (FSR = 2 x VREF) Output Data Format Output data is clocked out of DOUT in offset binary format on the falling edge of SCLK, MSB first (B15). For output binary codes, see the Transfer Function section and Figures 12, 13, and 14. 6 COMMON-MODE VOLTAGE (V) -2 INPUT VOLTAGE (V) 4 2 Configuring Analog Inputs Each analog input has two configurable parameters: 0 -2 -4 VREF = 4.096V -6 -8 -6 -4 -2 0 2 4 6 8 INPUT VOLTAGE (V) Figure 11. Common-Mode Voltage vs. Input Voltage (FSR = 4 x VREF) Start Bit Communication with the MAX1302/MAX1303 is accomplished using the three input data word formats shown in Table 3. Each input data word begins with a start bit. The start bit is defined as the first high bit clocked into DIN with CS low when any of the following are true: • Data conversion is not in process and all data from the previous conversion has clocked out of DOUT. • The device is configured for operation in external clock mode (mode 0) and previous conversion-result bits B15–B3 have clocked out of DOUT. • The device is configured for operation in external acquisition mode (mode 1) and previous conversionresult bits B15–B7 have clocked out of DOUT. • The device is configured for operation in internal clock mode, (mode 2) and previous conversionresult bits B15–B4 have clocked out of DOUT. • Single-ended or true-differential input • Input voltage range These parameters are configured using the analog input configuration byte as shown in Table 2. Each analog input has a dedicated register to store its input configuration information. The timing diagram of Figure 15 shows how to write to the analog input configuration registers. Figure 16 shows DOUT and SSTRB timing. Transfer Function An ADC’s transfer function defines the relationship between the analog input voltage and the digital output code. Figures 12, 13, and 14 show the MAX1302/ MAX1303 transfer functions. The transfer function is determined by the following characteristics: • Analog input voltage range • Single-ended or differential configuration • Reference voltage The axes of an ADC transfer function are typically in least significant bits (LSBs). For the MAX1302/MAX1303, an LSB is calculated using the following equation: 1 LSB = FSR × VREF 2N × 4.096V where N is the number of bits (N = 16) and FSR is the full-scale range (see Figures 7 and 8). ______________________________________________________________________________________ 21 MAX1302/MAX1303 COMMON-MODE VOLTAGE (V) 8-/4-Channel, ±VREF Multirange Inputs, Serial 16-Bit ADCs MAX1302/MAX1303 8-/4-Channel, ±VREF Multirange Inputs, Serial 16-Bit ADCs FSR FSR FFFF FFFE FFFD 8001 8000 7FFF 8001 FSR BINARY OUTPUT CODE (LSB [hex]) FFFE FFFD FSR BINARY OUTPUT CODE (LSB [hex]) FFFF 8000 7FFF 0003 0003 0002 0002 1 LSB = FSR x VREF 65,536 x 4.096V 0001 1 LSB = 0001 FSR x VREF 65,536 x 4.096V 0000 0000 -32,768 -32,766 -1 0 +1 0 +32,765 +32,767 1 2 3 32,768 65,533 65,535 INPUT VOLTAGE (LSB [DECIMAL]) (AGND1) AGND1 (DIF/SGL = 0) 0V (DIF/SGL = 1) Figure 13. Ideal Unipolar Transfer Function, Single-Ended Input, -FSR to 0 INPUT VOLTAGE (LSB [DECIMAL]) Figure 12. Ideal Bipolar Transfer Function, Single-Ended or Differential Input FSR FFFF FFFE 8001 FSR BINARY OUTPUT CODE (LSB [hex]) FFFD 8000 Selecting the Conversion Method The conversion method is selected using the mode-control byte (see the Mode Control section), and the conversion is initiated using a conversion start command (Table 3, and Figures 2, 3, and 4).The MAX1302/MAX1303 convert analog signals to digital data using one of three methods: • External Clock Mode, Mode 0 (Figure 2) • Highest maximum throughput (see the Electrical Characteristics table) 7FFF 0003 0002 1 LSB = 0001 FSR x VREF 65,536 x 4.096V 0000 0 1 2 3 32,768 • • Lowest maximum throughput (see the Electrical Characteristics table) 65,533 65,535 INPUT VOLTAGE (LSB [DECIMAL]) (AGND1) Figure 14. Ideal Unipolar Transfer Function, Single-Ended Input, 0 to +FSR Mode Control The MAX1302/MAX1303 contain one byte-wide modecontrol register. The timing diagram of Figure 15 shows how to use the mode-control byte, and the mode-control byte format is shown in Table 7. The mode-control byte is used to select the conversion method and to control the power modes of the MAX1302/MAX1303. 22 • User controls the sample instant • CS remains low during the conversion • User supplies SCLK throughout the ADC conversion and reads data at DOUT External Acquisition Mode, Mode 1 (Figure 3) • • User controls the sample instant • User supplies two bytes of SCLK, then drives CS high to relieve processor load while the ADC converts • After SSTRB transitions high, the user supplies two bytes of SCLK and reads data at DOUT Internal Clock Mode, Mode 2 (Figure 4) • High maximum throughput (see the Electrical Characteristics table) • The internal clock controls the sampling instant ______________________________________________________________________________________ 8-/4-Channel, ±VREF Multirange Inputs, Serial 16-Bit ADCs CS tCL tCH tCSH 1 SCLK 8 tCP tDS DIN START SEL2 SEL1 SEL0 1 8 tDH DIF/SGL R2 R1 R0 START M2 ANALOG INPUT CONFIGURATION BYTE tDV DOUT M1 M0 1 0 0 0 MODE CONTROL BYTE tTR HIGH IMPEDANCE HIGH IMPEDANCE HIGH IMPEDANCE Figure 15. Analog Input Configuration Byte and Mode-Control Byte Timing SSTRB tSSCS CS tCSS SCLK tDO DOUT HIGH IMPEDANCE MSB NOTE: SSTRB AND CS REMAIN LOW IN EXTERNAL CLOCK MODE (MODE 0). External Clock Mode (Mode 0) The MAX1302/MAX1303’s fastest maximum throughput rate is achieved operating in external clock mode. SCLK controls both the acquisition and conversion of the analog signal, facilitating precise control over when the analog signal is captured. The analog input sampling instant is at the falling edge of the 14th SCLK (Figure 2). Since SCLK drives the conversion in external clock mode, the SCLK frequency should remain constant while the conversion is clocked. The minimum SCLK frequency prevents droop in the internal sampling capacitor voltages during conversion. SSTRB remains low in the external clock mode, and as a result may be left unconnected if the MAX1302/ MAX1303 will always be used in the external clock mode. Figure 16. DOUT and SSTRB Timing • User supplies one byte of SCLK, then drives CS high to relieve processor load while the ADC converts • After SSTRB transitions high, the user supplies two bytes of SCLK and reads data at DOUT Table 7. Mode-Control Byte BIT NUMBER BIT NAME DESCRIPTION 7 START 6 M2 5 M1 4 M0 3 1 Bit 3 must be a logic 1 for the mode-control byte. 2 0 Bit 2 must be a logic 0 for the mode-control byte. 1 0 Bit 1 must be a logic 0 for the mode-control byte. 0 0 Bit 0 must be a logic 0 for the mode-control byte. Start Bit. The first logic 1 after CS goes low defines the beginning of the mode-control byte. Mode-Control Bits. M[2:0] select the mode of operation as shown in Table 8. ______________________________________________________________________________________ 23 MAX1302/MAX1303 tCSPW tCSS MAX1302/MAX1303 8-/4-Channel, ±VREF Multirange Inputs, Serial 16-Bit ADCs Table 8. Mode-Control Bits M[2:0] M2 M1 M0 0 0 0 External Clock (DEFAULT) MODE 0 0 1 External Acquisition 0 1 0 Internal Clock 0 1 1 Reserved 1 0 0 Reset 1 0 1 Reserved 1 1 0 Partial Power-Down 1 1 1 Full Power-Down External Acquisition Mode (Mode 1) The slowest maximum throughput rate is achieved with the external acquisition method. SCLK controls the acquisition of the analog signal in external acquisition mode, facilitating precise control over when the analog signal is captured. The internal clock controls the conversion of the analog input voltage. The analog input sampling instant is at the falling edge of the 16th SCLK (Figure 3). For the external acquisition mode, CS must remain low for the first 15 clock cycles and then rise on or after the falling edge of the 16th SCLK cycle as shown in Figure 3. For optimal performance, idle DIN and SCLK during the conversion. With careful board layout, transitions at DIN and SCLK during the conversion have a minimal impact on the conversion result. After the conversion is complete, SSTRB asserts high and CS can be brought low to read the conversion result. SSTRB returns low on the rising SCLK edge of the subsequent start bit. Internal Clock Mode (Mode 2) In internal clock mode, the internal clock controls both acquisition and conversion of the analog signal. The internal clock starts approximately 100ns to 400ns after the falling edge of the eighth SCLK and has a rate of about 4.5MHz. The analog input sampling instant occurs at the falling edge of the 11th internal clock signal (Figure 4). For the internal clock mode, CS must remain low for the first seven SCLK cycles and then rise on or after the falling edge of the eighth SCLK cycle. After the conversion is complete, SSTRB asserts high and CS can be brought low to read the conversion result. SSTRB returns low on the rising SCLK edge of the subsequent start bit. 24 Reset (Mode 4) As shown in Table 8, set M[2:0] = 100 to reset the MAX1302/MAX1303 to its default conditions. The default conditions are full power operation with each channel configured for ±VREF, bipolar, single-ended conversions using external clock mode (mode 0). Partial Power-Down Mode (Mode 6) As shown in Table 8, when M[2:0] = 110, the device enters partial power-down mode. In partial powerdown, all analog portions of the device are powered down except for the reference voltage generator and bias supplies. To exit partial power-down, change the mode by issuing one of the following mode-control bytes (see the Mode Control section): • External-clock-mode control byte • External-acquisition-mode control byte • Internal-clock-mode control byte • Reset byte • Full power-down-mode control byte This prevents the MAX1302/MAX1303 from inadvertently exiting partial power-down mode because of a CS glitch in a noisy digital environment. Full Power-Down Mode (Mode 7) When M[2:0] = 111, the device enters full power-down mode and the total supply current falls to 1µA (typ). In full power-down, all analog portions of the device are powered down. When using the internal reference, upon exiting full power-down mode, allow 10ms for the internal reference voltage to stabilize prior to initiating a conversion. To exit full power-down, change the mode by issuing one of the following mode-control bytes (see the Mode Control section): • External-clock-mode control byte ______________________________________________________________________________________ 8-/4-Channel, ±VREF Multirange Inputs, Serial 16-Bit ADCs REF. When using the internal reference, bypass REFCAP with a 0.1µF or greater capacitor to AGND1 and bypass REF with a 1.0µF or greater capacitor to AGND1. • Partial power-down-mode control byte This prevents the MAX1302/MAX1303 from inadvertently exiting full power-down mode because of a CS glitch in a noisy digital environment. External Reference For external reference operation, disable the internal reference and reference buffer by connecting REFCAP to AV DD1 . With AV DD1 connected to REFCAP, REF becomes a high-impedance input and accepts an external reference voltage. The MAX1302/MAX1303 external reference current varies depending on the applied reference voltage and the operating mode (see the External Reference Input Current vs. External Reference Input Voltage in the Typical Operating Characteristics). Power-On Reset The MAX1302/MAX1303 power up in normal operation configured for external clock mode with all circuitry active (Tables 7 and 8). Each analog input channel (CH0–CH7) is set for single-ended conversions with a ±VREF bipolar input range (Table 6). Allow the power supplies to stabilize after power-up. Do not initiate any conversions until the power supplies have stabilized. Additionally, allow 10ms for the internal reference to stabilize when CREF = 1.0µF and CRECAP = 0.1µF. Larger reference capacitors require longer stabilization times. Internal or External Reference The MAX1302/MAX1303 operate with either an internal or external reference. The reference voltage impacts the ADC’s FSR (Figures 12, 13, and 14). An external reference is recommended if more accuracy is required than the internal reference provides, and/or multiple converters require the same reference voltage. Internal Reference The MAX1302/MAX1303 contain an internal 4.096V bandgap reference. This bandgap reference is connected to REFCAP through a nominal 5kΩ resistor (Figure 17). The voltage at REFCAP is buffered creating 4.096V at 4.096V SAR ADC REF REF 1.0µF 1x REFCAP MAX1302 MAX1303 Applications Information Noise Reduction Additional samples can be taken and averaged (oversampling) to remove the effect of transition noise on conversion results. The square root of the number of samples determines the improvement in performance. For example, with 2/3 LSB RMS (4 LSBP-P) transition noise, 16 (42 = 16) samples must be taken to reduce the noise to 1 LSBP-P. Interface with 4–20mA Signals Figure 19 illustrates a simple interface between the MAX1302/MAX1303 and a 4–20mA signal. 4–20mA signaling can be used as a binary switch (4mA represents a logic-low signal, 20mA represents a logic-high signal), or for precision communication where currents between 4mA and 20mA represent intermediate analog data. For binary switch applications, connect the 4–20mA signal to the MAX1302/MAX1303 with a resistor to ground. For example, a 200Ω resistor converts the 4–20mA signal to a 0.8V to 4V signal. Adjust the resistor value so the parallel combination of the resistor and the MAX1302/MAX1303 source impedance is 200Ω. In this application, select the single-ended 0 to VREF range (R[2:0] = 011, Table 6). For applications that require precision measurements of continuous analog currents between 4mA and 20mA, use a buffer to prevent the MAX1302/MAX1303 input from diverting current from the 4–20mA signal. 0.1µF 5kΩ VRCTH 4.096V BANDGAP REFERENCE AGND1 Figure 17. Internal Reference Operation ______________________________________________________________________________________ 25 MAX1302/MAX1303 • External-acquisition-mode control byte • Internal-clock-mode control byte • Reset byte MAX1302/MAX1303 8-/4-Channel, ±VREF Multirange Inputs, Serial 16-Bit ADCs V+ 1.0µF IN 4.096V SAR ADC REF REF OUT 1.0µF MAX6341 AVDD1 1x REFCAP MAX1302 MAX1303 GND 5kΩ VRCTH 4.096V BANDGAP REFERENCE AGND1 Figure 18. External Reference Operation Bridge Application Layout, Grounding, and Bypassing The MAX1302/MAX1303 convert 1kHz signals more accurately than a similar sigma-delta converter that might be considered in bridge applications. The input impedance of the MAX1302, in combination with the current-limiting resistors, can affect the gain of the MAX1302. In many applications this error is acceptable, but for applications that cannot tolerate this error, the MAX1302 inputs can be buffered (Figure 20). Connect the bridge to a low-offset differential amplifier and then the true differential inputs of the MAX1302/MAX1303. Larger excitation voltages take advantage of more of the ±VREF/2 differential input voltage range. Select an input voltage range that matches the amplifier output. Be aware of the amplifier offset and offset-drift errors when selecting an appropriate amplifier. Careful PC board layout is essential for best system performance. Boards should have separate analog and digital ground planes and ensure that digital and analog signals are separated from each other. Do not run analog and digital (especially clock) lines parallel to one another, or digital lines underneath the device package. Figure 1 shows the recommended system ground connections. Establish an analog ground point at AGND1 and a digital ground point at DGND. Connect all analog grounds to the star analog ground. Connect the digital grounds to the star digital ground. Connect the digital ground plane to the analog ground plane at one point. For lowest noise operation, make the ground return to the star ground’s power-supply low impedance and as short as possible. Dynamically Adjusting the Input Range High-frequency noise in the AV DD1 power supply degrades the ADC’s high-speed comparator performance. Bypass AVDD1 to AGND1 with a 0.1µF ceramic surface-mount capacitor. Make bypass capacitor connections as short as possible. Software control of each channel’s analog input range and the unipolar endpoint overlap specification make it possible for the user to change the input range for a channel dynamically and improve performance in some applications. Changing the input range results in a small LSB step-size over a wider output voltage range. For example, by switching between a -VREF/2 to 0V range and a 0 to VREF/2 range, an LSB is: (VREF / 2) × VREF 65, 536 × 4.096 but the input voltage range effectively spans from -VREF/2 to +VREF/2 (FSR = +VREF). 26 Parameter Definitions Integral Nonlinearity (INL) INL is the deviation of the values on an actual transfer function from a straight line. This straight line is 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 MAX1302/MAX1303 INL is measured using the endpoint method. ______________________________________________________________________________________ 8-/4-Channel, ±VREF Multirange Inputs, Serial 16-Bit ADCs MAX1302/MAX1303 4–20mA INPUT CH0 µC 200Ω MAX1302 4–20mA INPUT CH8 200Ω Figure 19. 4–20mA Application LOW-OFFSET DIFFERENTIAL AMPLIFIER CH0 µP CH1 MAX1302 MAX1303 REF BRIDGE Figure 20. Bridge Application Differential Nonlinearity (DNL) Channel-to-Channel Isolation DNL is the difference between an actual step width and the ideal value of 1 LSB. A DNL error specification of greater than -1 LSB guarantees no missing codes and a monotonic transfer function. Channel-to-channel isolation indicates how well each analog input is isolated from the others. The channel-tochannel isolation for these devices is measured by applying a near full-scale magnitude 5kHz sine wave to the selected analog input channel while applying an equal magnitude sine wave of a different frequency to all unselected channels. An FFT of the selected channel output is used to determine the ratio of the magnitudes of the signal applied to the unselected channels and the 5kHz signal applied to the selected analog input channel. This ratio is reported, in dB, as channelto-channel isolation. Transition Noise Transition noise is the amount of noise that appears at a code transition on the ADC transfer function. Conversions performed with the analog input right at the code transition can result in code flickering in the LSBs. ______________________________________________________________________________________ 27 MAX1302/MAX1303 8-/4-Channel, ±VREF Multirange Inputs, Serial 16-Bit ADCs Unipolar Offset Error -FSR to 0V When a zero-scale analog input voltage is applied to the converter inputs, the digital output is all ones (0xFFFF). Ideally, the transition from 0xFFFF to 0xFFFE occurs at AGND1 - 0.5 LSB. Unipolar offset error is the amount of deviation between the measured zero-scale transition point and the ideal zero-scale transition point, with all untested channels grounded. 0V to +FSR When a zero-scale analog input voltage is applied to the converter inputs, the digital output is all zeros (0x0000). Ideally, the transition from 0x0000 to 0x0001 occurs at AGND1 + 0.5 LSB. Unipolar offset error is the amount of deviation between the measured zero-scale transition point and the ideal zero-scale transition point, with all untested channels grounded. Bipolar Offset Error When a zero-scale analog input voltage is applied to the converter inputs, the digital output is a one followed by all zeros (0x8000). Ideally, the transition from 0x7FFF to 0x8000 occurs at (2N-1 - 0.5) LSB. Bipolar offset error is the amount of deviation between the measured midscale transition point and the ideal midscale transition point, with untested channels grounded. Gain Error When a positive full-scale voltage is applied to the converter inputs, the digital output is all ones (0xFFFF). The transition from 0xFFFE to 0xFFFF occurs at 1.5 LSB below full scale. Gain error is the amount of deviation between the measured full-scale transition point and the ideal full-scale transition point with the offset error removed and all untested channels grounded. Unipolar Endpoint Overlap Unipolar endpoint overlap is the change in offset when switching between complementary input voltage ranges. For example, the difference between the voltage that results in a 0xFFFF output in the -VREF/2 to 0V input voltage range and the voltage that results in a 0x0000 output in the 0 to +VREF/2 input voltage range is the unipolar endpoint overlap. The unipolar endpoint overlap is positive for the MAX1302/MAX1303, preventing loss of signal or a dead zone when switching between adjacent analog input voltage ranges. Small-Signal Bandwidth A 100mVP-P sine wave is applied to the ADC, and the input frequency is then swept up to the point where the amplitude of the digitized conversion result has decreased by -3dB. 28 Full-Power Bandwidth A 95% of full-scale sine wave is applied to the ADC, and the input frequency is then swept up to the point where the amplitude of the digitized conversion result has decreased by -3dB. Common-Mode Rejection Ratio (CMRR) CMRR is the ability of a device to reject a signal that is “common” to or applied to both input terminals. The common-mode signal can be either an AC or a DC signal or a combination of the two. CMR is expressed in decibels. Common-mode rejection ratio is the ratio of the differential signal gain to the common-mode signal gain. CMRR applies only to differential operation. Power-Supply Rejection Ratio (PSRR) PSRR is the ratio of the output-voltage shift to the power-supply-voltage shift for a fixed input voltage. For the MAX1302/MAX1303, AVDD1 can vary from 4.75V to 5.25V. PSRR is expressed in decibels and is calculated using the following equation: 5.25V − 4.75V PSRR[dB] = 20 × log VOUT (5.25V) − VOUT (4.75V) For the MAX1302/MAX1303, PSRR is tested in bipolar operation with the analog inputs grounded. Aperture Jitter Aperture jitter, tAJ, is the statistical distribution of the variation in the sampling instant (Figure 21). Aperture Delay Aperture delay, tAD, is the time from the falling edge of SCLK to the sampling instant (Figure 21). Signal-to-Noise Ratio (SNR) SNR is computed by taking the ratio of the RMS signal to the RMS noise. RMS noise includes all spectral components to the Nyquist frequency excluding the fundamental, the first five harmonics, and the DC offset. Signal-to-Noise Plus Distortion (SINAD) SINAD is computed by taking the ratio of the RMS signal to the RMS noise plus distortion. RMS noise plus distortion includes all spectral components to the Nyquist frequency excluding the fundamental and the DC offset. SignalRMS SINAD(dB) = 20 × log NoiseRMS ______________________________________________________________________________________ 8-/4-Channel, ±VREF Multirange Inputs, Serial 16-Bit ADCs SINAD − 1.76 ENOB = 6.02 SCLK (MODE 0) 13 14 SCLK (MODE 1) 15 16 INTCLK (MODE 2) 10 11 MAX1302/MAX1303 Effective Number of Bits (ENOB) ENOB indicates the global accuracy of an ADC at a specific input frequency and sampling rate. With an input range equal to the ADC’s full-scale range, calculate the ENOB as follows: 15 12 Total Harmonic Distortion (THD) For the MAX1302/MAX1303, THD is the ratio of the RMS sum of the input signal’s first four harmonic components to the fundamental itself. This is expressed as: V2 2 + V3 2 + V4 2 + V5 2 THD = 20 × log V1 tAJ tAD SAMPLE INSTANT ANALOG INPUT TRACK AND HOLD TRACK HOLD Figure 21. Aperture Diagram where V1 is the fundamental amplitude, and V2 through V5 are the amplitudes of the 2nd- through 5th-order harmonic components. Spurious-Free Dynamic Range (SFDR) SFDR is the ratio of RMS amplitude of the fundamental (maximum signal component) to the RMS value of the next-largest spectral component. ______________________________________________________________________________________ 29 8-/4-Channel, ±VREF Multirange Inputs, Serial 16-Bit ADCs MAX1302/MAX1303 Block Diagram SERIAL I/O CONTROL LOGIC AND REGISTERS CH0 CH1 CH2 CH3 CH4 CH5 CH6 CH7 AGND1 AVDD2 CLOCK ANALOG INPUT MUX AND MULTIRANGE CIRCUITRY PGA IN SAR ADC OUT DVDD FIFO DGND AVDD1 AGND3 REF AGND2 4.096V BANDGAP REFERENCE 5kΩ 1x MAX1302 REFCAP REF Pin Configurations (continued) TOP VIEW AGND1 1 20 AGND2 AVDD1 2 19 AVDD2 CH0 3 18 AGND3 CH1 4 17 REF MAX1303 16 REFCAP CH3 6 15 DVDD CS 7 14 DVDDO DIN 8 13 DGND SSTRB 9 12 DGNDO SCLK 10 11 DOUT TSSOP 30 AVDD2 AGND2 Chip Information TRANSISTOR COUNT: 28,210 PROCESS: BiCMOS CH2 5 DVDDO CS DIN SSTRB DOUT SCLK DGNDO ______________________________________________________________________________________ 8-/4-Channel, ±VREF Multirange Inputs, Serial 16-Bit ADCs TSSOP4.40mm.EPS PACKAGE OUTLINE, TSSOP 4.40mm BODY 21-0066 G 1 1 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 ____________________ 31 © 2005 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products, Inc. MAX1302/MAX1303 Package Information (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information go to www.maxim-ic.com/packages.)