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19-2442; Rev 1; 10/02
2.7V to 5.5V, Low-Power, 4-/12-Channel 2-Wire Serial 8-Bit ADCs
General Description
The MAX1036-MAX1039 low-power, 8-bit, multichannel, analog-to-digital converters (ADCs) feature internal track/hold (T/H), voltage reference, clock, and an I2C-compatible 2-wire serial interface. These devices operate from a single supply and require only 350A at the maximum sampling rate of 188ksps. AutoShutdownTM powers down the devices between conversions reducing supply current to less than 1A at low throughput rates. The MAX1036/MAX1037 have four analog input channels each, while the MAX1038/MAX1039 have twelve analog input channels. The analog inputs are software configurable for unipolar or bipolar and singleended or pseudo-differential operation. The full-scale analog input range is determined by the internal reference or by an externally applied reference voltage ranging from 1V to V DD . The MAX1037/ MAX1039 feature a 2.048V internal reference and the MAX1036/MAX1038 feature a 4.096V internal reference. The MAX1036/MAX1037 are available in 8-pin SOT23 packages. The MAX1038/MAX1039 are available in 16pin QSOP packages. The MAX1036-MAX1039 are guaranteed over the extended industrial temperature range (-40C to +85C). Refer to MAX1136-MAX1139 for 10-bit devices and to the MAX1236-MAX1239 for 12-bit devices.
Features
o High-Speed I2C-Compatible Serial Interface 400kHz Fast Mode 1.7MHz High-Speed Mode o Single Supply 2.7V to 3.6V (MAX1037/MAX1039) 4.5V to 5.5V (MAX1036/MAX1038) o Internal Reference 2.048V (MAX1037/MAX1039) 4.096V (MAX1036/MAX1038) o External Reference: 1V to VDD o Internal Clock o 4-Channel Single-Ended or 2-Channel PseudoDifferential (MAX1036/MAX1037) o 12-Channel Single-Ended or 6-Channel PseudoDifferential (MAX1038/MAX1039) o Internal FIFO with Channel-Scan Mode o Low Power 350A at 188ksps 110A at 75ksps 8A at 10ksps 1A in Power-Down Mode o Software Configurable Unipolar/Bipolar o Small Packages 8-Pin SOT23 (MAX1036/MAX1037) 16-Pin QSOP (MAX1038/MAX1039)
Pin Configurations and Typical Operating Circuit appear at end of data sheet.
MAX1036-MAX1039
Applications
Hand-Held Portable Applications Medical Instruments Battery-Powered Test Equipment Solar-Powered Remote Systems Received-Signal-Strength Indicators System Supervision
Ordering Information
PART MAX1036EKA-T MAX1037EKA-T MAX1038AEEE MAX1039AEEE TEMP RANGE -40C to +85C -40C to +85C -40C to +85C -40C to +85C PIN-PACKAGE 8 SOT23-8 8 SOT23-8 16 QSOP 16 QSOP TUE (LSB) 2 2 1 1 INPUT CHANNELS 4 4 12 12 INTERNAL REFERENCE (V) 4.096 2.048 4.096 2.048 TOP MARK AAJE AAJG -- --
AutoShutdown is a trademark of Maxim Integrated Products, Inc.
________________________________________________________________ Maxim Integrated Products
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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.
2.7V to 5.5V, Low-Power, 4-/12-Channel 2-Wire Serial 8-Bit ADCs MAX1036-MAX1039
ABSOLUTE MAXIMUM RATINGS
VDD to GND ..............................................................-0.3V to +6V AIN0-AIN11, REF to GND ......................-0.3V to the lower of (VDD + 0.3V) and +6V SDA, SCL to GND.....................................................-0.3V to +6V Maximum Current Into Any Pin .........................................50mA Continuous Power Dissipation (TA = +70C) 8-Pin SOT23 (derate 7.1mW/C above +70C).............567mW 16-Pin QSOP (derate 8.3mW/C above +70C).........666.7mW Operating Temperature Range ...........................-40C to +85C Junction Temperature ......................................................+150C Storage Temperature Range .............................-60C to +150C Lead Temperature (soldering, 10s) .................................+300C
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
(V DD = 2.7V to 3.6V (MAX1037/MAX1039), V DD = 4.5V to 5.5V (MAX1036/MAX1038). External reference, V REF = 2.048V (MAX1037/MAX1039), VREF = 4.096V (MAX1036/MAX1038). External clock, fSCL = 1.7MHz, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25C.)
PARAMETER DC ACCURACY (Note 1) Resolution Relative Accuracy Differential Nonlinearity Offset Error Offset Error Temperature Coefficient Gain Error Gain Temperature Coefficient Total Unadjusted Error Channel-to-Channel Offset Matching Channel-to-Channel Gain Matching Input Common-Mode Rejection Ratio Signal-to-Noise Plus Distortion Total Harmonic Distortion Spurious-Free Dynamic Range Channel-to-Channel Crosstalk Full-Power Bandwidth Full-Linear Bandwidth CONVERSION RATE Conversion Time (Note 5) tCONV Internal clock External clock 4.7 6.1 s CMRR Pseudo-differential input mode TUE MAX1036/MAX1037 MAX1038A/MAX1039A (Note 3) 1 0.5 0.5 0.1 0.5 75 2 1 3 1 INL DNL (Note 2) No missing codes over temperature 8 1 1 1.5 Bits LSB LSB LSB ppm/C LSB ppm/C LSB LSB LSB dB SYMBOL CONDITIONS MIN TYP MAX UNITS
DYNAMIC PERFORMANCE (fIN(sine wave) = 25kHz, VIN = VREF(P-P), fSAMPLE = 188ksps, RIN = 100) SINAD THD SFDR (Note 4) -3dB point SINAD > 49dB Up to the 5th harmonic 49 -69 69 75 2.0 200 dB dB dB dB MHz kHz
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2.7V to 5.5V, Low-Power, 4-/12-Channel 2-Wire Serial 8-Bit ADCs
ELECTRICAL CHARACTERISTICS (continued)
(V DD = 2.7V to 3.6V (MAX1037/MAX1039), V DD = 4.5V to 5.5V (MAX1036/MAX1038). External reference, V REF = 2.048V (MAX1037/MAX1039), VREF = 4.096V (MAX1036/MAX1038). External clock, fSCL = 1.7MHz, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25C.)
PARAMETER SYMBOL CONDITIONS Internal clock, SCAN[1:0] = 01 (MAX1036/MAX1037) Throughput Rate fSAMPLE Internal clock, SCAN[1:0] = 00 CS[3:0] = 1011 (MAX1038/MAX1039) External clock Track/Hold Acquisition Time Internal Clock Frequency Aperture Delay ANALOG INPUT (AIN0-AIN11) Input Voltage Range, Single Ended and Differential (Note 6) Input Multiplexer Leakage Current Input Capacitance INTERNAL REFERENCE (Note 7) Reference Voltage Reference Temperature Coefficient Reference Short-Circuit Current Reference Source Impedance EXTERNAL REFERENCE Reference Input Voltage Range REF Input Current Input High Voltage Input Low Voltage Input Hysteresis Input Current Input Capacitance Output Low Voltage VREF IREF VIH VIL VHYST IIN CIN VOL ISINK = 3mA VIN = 0 to VDD 15 0.4 0.1 x VDD 10 (Note 9) fSAMPLE = 188ksps 0.7 x VDD 0.3 x VDD 1.0 14 VDD 30 V A V V V A pF V (Note 8) 675 VREF TCREF TA = +25C MAX1037/MAX1039 MAX1036/MAX1038 1.925 3.850 2.048 4.096 120 10 2.171 4.342 V ppm/C mA CIN Unipolar Bipolar On/off-leakage current, VAIN_= 0 or VDD, no clock, fSCL = 0 0.01 18 0 VREF VREF / 2 1 V A pF tAD External clock, fast mode External clock, high-speed mode 588 2.25 45 30 MIN TYP MAX 76 77 188 ns MHz ns ksps UNITS
MAX1036-MAX1039
DIGITAL INPUTS/OUTPUTS (SCL, SDA)
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2.7V to 5.5V, Low-Power, 4-/12-Channel 2-Wire Serial 8-Bit ADCs MAX1036-MAX1039
ELECTRICAL CHARACTERISTICS (continued)
(V DD = 2.7V to 3.6V (MAX1037/MAX1039), V DD = 4.5V to 5.5V (MAX1036/MAX1038). External reference, V REF = 2.048V (MAX1037/MAX1039), VREF = 4.096V (MAX1036/MAX1038). External clock, fSCL = 1.7MHz, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25C.)
PARAMETER POWER REQUIREMENTS Supply Voltage (Note 10) VDD MAX1037/MAX1039 MAX1036/MAX1038 fSAMPLE = 188ksps fSAMPLE = 75ksps Supply Current IDD fSAMPLE = 10ksps fSAMPLE = 1ksps Power-down Power-Supply Rejection Ratio Serial Clock Frequency Bus Free Time Between a STOP and a START Condition Hold Time for Start Condition Low Period of the SCL Clock High Period of the SCL Clock Setup Time for a Repeated START Condition (Sr) Data Hold Time Data Setup Time Rise Time of Both SDA and SCL Signals, Receiving Fall Time of SDA Transmitting Setup Time for STOP Condition Capacitive Load for Each Bus Line Pulse Width of Spike Suppressed Serial Clock Frequency Hold Time (Repeated) Start Condition Low Period of the SCL Clock High Period of the SCL Clock PSRR fSCL tBUF tHD, STA tLOW tHIGH tSU, STA tHD, DAT tSU, DAT tR tF tSU, STO CB tSP fSCLH tHD, STA tLOW tHIGH (Note 14) 160 320 120 (Note 13) (Note 13) (Note 12) 1.3 0.6 1.3 0.6 0.6 0 100 20 + 0.1CB 20 + 0.1CB 0.6 400 50 1.7 300 300 150 (Note 11) TIMING CHARACTERISTICS FOR 2-WIRE FAST MODE (Figures 1A and 2) 400 kHz s s s s s ns ns ns ns s pF ns MHz ns ns ns Internal REF, external clock External REF, external clock External REF, external clock External REF, internal clock External REF, external clock External REF, internal clock External REF, external clock External REF, internal clock 2.7 4.5 350 250 110 150 8 10 2 2.5 1 0.25 10 1 LSB/V A 3.6 5.5 650 V SYMBOL CONDITIONS MIN TYP MAX UNITS
TIMING CHARACTERISTICS FOR 2-WIRE HIGH-SPEED MODE (Figures 1B and 2)
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2.7V to 5.5V, Low-Power, 4-/12-Channel 2-Wire Serial 8-Bit ADCs
ELECTRICAL CHARACTERISTICS (continued)
(V DD = 2.7V to 3.6V (MAX1037/MAX1039), V DD = 4.5V to 5.5V (MAX1036/MAX1038). External reference, V REF = 2.048V (MAX1037/MAX1039), VREF = 4.096V (MAX1036/MAX1038). External clock, fSCL = 1.7MHz, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25C.)
PARAMETER Setup Time for a Repeated START Condition (Sr) Data Hold Time Data Setup Time Rise Time of SCL Signal (Current Source Enabled) Rise Time of SCL Signal After Acknowledge Bit Fall Time of SCL Signal Rise Time of SDA Signal Fall Time of SDA Signal Setup Time for STOP Condition Capacitive Load for Each Bus Line Pulse Width of Spike Suppressed SYMBOL tSU, STA tHD, DAT tSU, DAT tRCL tRCL1 tFCL tRDA tFDA tSU, STO CB tSP 0 (Note 13) (Note 13) (Note 13) (Note 13) (Note 13) (Note 12) CONDITIONS MIN 160 0 10 20 20 20 20 20 160 400 10 80 160 80 160 160 150 TYP MAX UNITS ns ns ns ns ns ns ns ns ns pF ns
MAX1036-MAX1039
Note 1: The MAX1036/MAX1038 are tested at VDD = 5V and the MAX1037/MAX1039 are tested at VDD = 3V. All devices are configured for unipolar, single-ended inputs. Note 2: Relative accuracy is the deviation of the analog value at any code from its theoretical value after the full-scale range and offsets have been calibrated. Note 3: Offset nulled. Note 4: Ground ON channel; sine wave applied to all OFF channels. Note 5: Conversion time is defined as the number of clock cycles (8) multiplied by the clock period. Conversion time does not include acquisition time. SCL is the conversion clock in the external clock mode. Note 6: The absolute voltage range for the analog inputs (AIN0-AIN11) is from GND to VDD. Note 7: When AIN_/REF is configured to be an internal reference (SEL[2:1] = 11), decouple AIN_/REF to GND with a 0.01F capacitor. Note 8: The switch connecting the reference buffer to AIN_/REF has a typical on-resistance of 675. Note 9: ADC performance is limited by the converter's noise floor, typically 1.4mVP-P. Note 10: Electrical characteristics are guaranteed from VDD(min) to VDD(max). For operation beyond this range, see the Typical Operating Characteristics. Note 11: Power-supply rejection ratio is measured as:
[VFS (3.3V) - VFS (2.7V)] x V2 REF
, for the MAX1037/MAX1039 where N is the number of bits (8) and VREF = 2.048V. Power-supply rejection ratio is measured as:
3.3V - 2.7V
N
[VFS (5.5V) - VFS (4.5V)] x V2 REF
, for the MAX1036/MAX1038 where N is the number of bits (8) and VREF = 2.048V. Note 12: A master device must provide a data hold time for SDA (referred to VIL of SCL) in order to bridge the undefined region of SCL's falling edge (Figure 1). Note 13: CB = total capacitance of one bus line in pF. tR and tF measured between 0.3VDD and 0.7VDD. Minimum specification is tested at +25C with CB = 400pF. Note 14: fSCLH must meet the minimum clock low time plus the rise/fall times. _______________________________________________________________________________________ 5
5.5V - 4.5V
N
2.7V to 5.5V, Low-Power, 4-/12-Channel 2-Wire Serial 8-Bit ADCs MAX1036-MAX1039
Typical Operating Characteristics
(VDD = 3.3V (MAX1037/MAX1039), VDD = 5V (MAX1036/MAX1038), fSCL = 1.7MHz, external clock (33% duty cycle), fSAMPLE = 188ksps, single ended, unipolar, TA = +25C, unless otherwise noted.)
SUPPLY CURRENT vs. VOLTAGE
MAX1036 toc01
SUPPLY CURRENT vs. TEMPERATURE
MAX1036 toc02
SHUTDOWN SUPPLY CURRENT vs. SUPPLY VOLTAGE
SDA = SCL = VDD 4
MAX1036 toc03
450 400 350 IDD (A) A) INTERNAL 4.096VREF B) INTERNAL 2.048VREF C) EXTERNAL 4.096VREF D) EXTERNAL 2.048VREF
450 400 INTERNAL 4.096VREF 350 IDD (A) 300 250 INTERNAL 2.048VREF EXTERNAL 4.096VREF
5
A B
300 C 250 D 200 150 2.5 3.0 3.5 4.0 VDD (V) 4.5 5.0 5.5
IDD (A) 60 85
3
2
200 150 -40
EXTERNAL 2.048VREF
1
0 -15 10 35 2.5 3.0 3.5 4.0 VDD (V) 4.5 5.0 5.5 TEMPERATURE (C)
SHUTDOWN SUPPLY CURRENT vs. TEMPERATURE
MAX1036 toc04
AVERAGE SUPPLY CURRENT vs. CONVERSION RATE (INTERNAL CLOCK)
MAX1036 toc05
AVERAGE SUPPLY CURRENT VS. CONVERSION RATE (EXTERNAL CLOCK)
450 400 AVERAGE IDD (A) 350 300 250 200 150 100 EXTERNAL CLOCK MODE fSCL = 1.7MHz 0 50 100 150 200 C A) INTERNAL REF ALWAYS ON B) INTERNAL REF AUTOSHUTDOWN C) EXTERNAL REF A B
MAX1036 toc06
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SDA = SCL = VDD
350 300 AVERAGE IDD (A) 250 B 200 C 150 100 50 INTERNAL CLOCK MODE fSCL = 1.7MHz 0 10 20 30 40 50 A) INTERNAL REF ALWAYS ON B) INTERNAL REF AUTOSHUTDOWN C) EXTERNAL REF A
500
4
IDD (A)
3
2 VDD = 5V 1 VDD = 3.3V 0 -40 -15 10 35 60 85 TEMPERATURE (C)
50 0 60
0 CONVERSION RATE (ksps)
CONVERSION RATE (ksps)
NORMALIZED 4.096V REFERENCE VOLTAGE vs. SUPPLY VOLTAGE
1.0075 1.0050 VREF NORMALIZED VREF NORMALIZED 1.0025 1.0000 0.9975 0.9950 0.9925 0.9900 4.00 4.25 4.50 4.75 VDD (V) 5.00 5.25 5.50
MAX1036 toc7
INTERNAL 4.096V REFERENCE VOLTAGE vs. TEMPERATURE
MAX1036 toc08
INTERNAL 2.048V REFERENCE VOLTAGE vs. SUPPLY VOLTAGE
1.0075 1.0050
VREF NORMALIZED
MAX1036 toc09
1.0100
1.020 1.015 1.010 1.005 1.000 0.995 0.990 0.985 0.980 -40 -15 10 35 60
1.0100
1.0025 1.0000 0.9975 0.9950 0.9925 0.9900
85
2.5
3.0
3.5
4.0 VDD (V)
4.5
5.0
5.5
TEMPERATURE (C)
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2.7V to 5.5V, Low-Power, 4-/12-Channel 2-Wire Serial 8-Bit ADCs MAX1036-MAX1039
Typical Operating Characteristics (continued)
(VDD = 3.3V (MAX1037/MAX1039), VDD = 5V (MAX1036/MAX1038), fSCL = 1.7MHz, external clock (33% duty cycle), fSAMPLE = 188ksps, single ended, unipolar, TA = +25C, unless otherwise noted.)
INTERNAL 2.048V REFERENCE VOLTAGE vs. TEMPERATURE
MAX1036 toc10
DIFFERENTIAL NONLINEARITY vs. DIGITAL CODE
MAX1036 toc11
INTEGRAL NONLINEARITY vs. DIGITAL CODE
0.4 0.3 0.2 INL (LSB) 0.1 0 -0.1 -0.2 -0.3 -0.4 -0.5
MAX1036 toc12
1.020 1.015 1.010
VREF NORMALIZED
0.5 0.4 0.3 0.2 DNL (LSB) 0.1 0 -0.1 -0.2
0.5
1.005 1.000 0.995 0.990 0.985 0.980 -40 -15 10 35 60 85 TEMPERATURE (C)
-0.3 -0.4 -0.5 0 50 100 150 200 250 300 DIGITAL OUTPUT CODE
0
50
100
150
200
250
300
DIGITAL OUTPUT CODE
FFT PLOT
MAX1036 toc13
OFFSET ERROR vs. SUPPLY VOLTAGE
0.9 0.8 OFFSET ERROR (LSB) 0.7 0.6 0.5 0.4 0.3 0.2 0.1 VREF = 2.048V
MAX1036 toc14
0 -20 AMPLITUDE (dBc) -40 -60 -80 -100 -120 0 20k 40k
1.0
fSAMPLE = 188ksps fIN = 25kHz
0 60k 80k 100k 2.5 3.0 3.5 4.0 VDD (V) 4.5 5.0 5.5 FREQUENCY (Hz)
OFFSET ERROR vs. TEMPERATURE
MAX1036 toc15
GAIN ERROR vs. SUPPLY VOLTAGE
-0.01 -0.02 GAIN ERROR (LSB) -0.03 -0.04 -0.05 -0.06 -0.07 -0.08 -0.09 -0.1 VREF = 2.048V
MAX1036 toc16
1.0 0.9 0.8 OFFSET ERROR (LSB) 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 -40 -15 10 35 60 VDD = 3.3V VREF = 2.048V
0
85
2.5
3.0
3.5
4.0 VDD (V)
4.5
5.0
5.5
TEMPERATURE (C)
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2.7V to 5.5V, Low-Power, 4-/12-Channel 2-Wire Serial 8-Bit ADCs MAX1036-MAX1039
Pin Description
PIN MAX1036/ MAX1037 1, 2, 3 -- -- 4 -- 5 6 7 8 MAX1038/ MAX1039 8, 7, 6 5, 4, 3, 2, 1 16, 15, 14 -- 13 9 10 11 12 NAME AIN0-AIN2 AIN3-AIN7 AIN8-AIN10 AIN3/REF AIN11/REF SCL SDA GND VDD Analog Input 3/Reference Input or Output. Selected in the setup register. Analog Input 11/Reference Input or Output. Selected in the setup register. Clock Input Data Input/Output Ground Positive Supply. Bypass to GND with a 0.1F capacitor. Analog Inputs FUNCTION
Detailed Description
The MAX1036-MAX1039 ADCs use successiveapproximation conversion techniques and input T/H circuitry to capture and convert an analog signal to a serial 8-bit digital output. The MAX1036/MAX1037 are 4-channel ADCs, and the MAX1038/MAX1039 are 12channel ADCs. These devices feature a high-speed 2wire serial interface supporting data rates up to 1.7MHz. Figure 3 shows the simplified functional diagram for the MAX1038/MAX1039.
Power Supply
The MAX1036-MAX1039 operate from a single supply and consume 350A at sampling rates up to 188ksps. The MAX1037/MAX1039 feature a 2.048V internal reference and the MAX1036/MAX1038 feature a 4.096V internal reference. All devices can be configured for use with an external reference from 1V to VDD.
Analog Input and Track/Hold
The MAX1036-MAX1039 analog input architecture contains an analog input multiplexer (MUX), a T/H capacitor, T/H switches, a comparator, and a switched capacitor digital-to-analog converter (DAC) (Figure 4). In single-ended mode, the analog input multiplexer connects CT/H to the analog input selected by CS[3:0] (see the Configuration/Setup Bytes (Write Cycle) section). The charge on CT/H is referenced to GND when converted. In pseudo-differential mode, the analog input multiplexer connects C T/H to the `+' analog input selected by CS[3:0]. The charge on CT/H is referenced to the `-' analog input when converted.
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The MAX1036-MAX1039 input configuration is pseudodifferential in that only the signal at the `+' analog input is sampled with the T/H circuitry. The `-' analog input signal must remain stable within 0.5LSB (0.1LSB for best results) with respect to GND during a conversion. To accomplish this, connect a 0.1F capacitor from `-' analog input to GND. See the Single-Ended/PseudoDifferential Input section. During the acquisition interval, the T/H switches are in the track position and CT/H charges to the analog input signal. At the end of the acquisition interval, the T/H switches move to the hold position retaining the charge on CT/H as a sample of the input signal. During the conversion interval, the switched capacitive DAC adjusts to restore the comparator input voltage to zero within the limits of 8-bit resolution. This action requires eight conversion clock cycles and is equivalent to transferring a charge of 18pF (VIN+ - VIN-) from CT/H to the binary weighted capacitive DAC forming a digital representation of the analog input signal. Sufficiently low source impedance is required to ensure an accurate sample. A source impedance below 1.5k does not significantly degrade sampling accuracy. To minimize sampling errors with higher source impedances, connect a 100pF capacitor from the analog input to GND. This input capacitor forms an RC filter with the source impedance limiting the analog input bandwidth. For larger source impedances, use a buffer amplifier to maintain analog input signal integrity. When operating in internal clock mode, the T/H circuitry enters its tracking mode on the ninth falling clock edge
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2.7V to 5.5V, Low-Power, 4-/12-Channel 2-Wire Serial 8-Bit ADCs MAX1036-MAX1039
A. F/S-MODE I2C SERIAL INTERFACE TIMING tR tF t
SDA
tSU.DAT tLOW
tHD.DAT tSU.STA
tHD.STA tSU.STO
tBUF
SCL
tHD.STA tR S B. HS-MODE I2C SERIAL INTERFACE TIMING
tHIGH tF Sr A P S
tRDA
tFDA
SDA
tSU.DAT tLOW
tHD.DAT tSU.STA
tHD.STA
tBUF tSU.STO
SCL
tHD.STA tRCL S
tHIGH tFCL Sr A tRCL1 S
HS-MODE
F/S-MODE
Figure 1. I2C Serial Interface Timing
of the address byte (see the Slave Address section). The T/H circuitry enters hold mode two internal clock cycles later. A conversion or series of conversions are then internally clocked (eight clock cycles per conversion) and the MAX1036-MAX1039 hold SCL low. When operating in external clock mode, the T/H circuitry enters track mode on the seventh falling edge of a valid slave address byte. Hold mode is then entered on the falling edge of the eighth clock cycle. The conversion is performed during the next eight clock cycles. The time required for the T/H circuitry to acquire an input signal is a function of input capacitance. If the analog input source impedance is high, the acquisition time lengthens and more time must be allowed between conversions. The acquisition time (tACQ) is the minimum time needed for the signal to be acquired. It is calculated by: tACQ 6.25 (RSOURCE + RIN) CIN where RSOURCE is the analog input source impedance, RIN = 2.5k, and CIN = 18pF. tACQ is 1/fSCL for external
VDD IOL = 3mA
SDA
VOUT 400pF
IOH = 0mA
Figure 2. Load Circuit
clock mode. For internal clock mode, the acquisition time is two internal clock cycles. To select RSOURCE, allow 625ns for tACQ in internal clock mode to account for clock frequency variations.
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2.7V to 5.5V, Low-Power, 4-/12-Channel 2-Wire Serial 8-Bit ADCs MAX1036-MAX1039
SDA SCL INPUT SHIFT REGISTER VDD SETUP REGISTER GND CONFIGURATION REGISTER CONTROL LOGIC INTERNAL OSCILLATOR
AIN0 AIN1 AIN2 AIN3 AIN4 AIN5 AIN6 AIN7 AIN8 AIN9 AIN10 AIN11/REF
T/H
8-BIT ADC
OUTPUT SHIFT REGISTER AND 12-BYTE RAM
ANALOG INPUT MUX
REF
REFERENCE 4.096V (MAX1038) 2.048V (MAX1039)
MAX1038 MAX1039
Figure 3. MAX1038/MAX1039 Simplified Functional Diagram
ANALOG INPUT MUX CT/H AIN0
REF
TRACK
AIN1
HOLD
CAPACITIVE DAC
TRACK
AIN3/REF
GND
DIFFERENTIAL
SINGLE ENDED
AIN2
HOLD
MAX1036 MAX1037
Figure 4. Equivalent Input Circuit
Analog Input Bandwidth
The MAX1036-MAX1039 feature input tracking circuitry with a 2MHz small signal-bandwidth. The 2MHz input bandwidth makes it possible to digitize high-speed 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.
Analog Input Range and Protection
Internal protection diodes clamp the analog input to VDD and GND. These diodes allow the analog inputs to swing from (GND - 0.3V) to (VDD + 0.3V) without causing damage to the device. For accurate conversions, the inputs must not go more than 50mV below GND or above VDD. If the analog input exceeds VDD by more than 50mV, the input current should be limited to 2mA.
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2.7V to 5.5V, Low-Power, 4-/12-Channel 2-Wire Serial 8-Bit ADCs MAX1036-MAX1039
Table 1. Setup Byte Format
BIT 7 (MSB) REG BIT 7 6 5 4 3 2 1 0 BIT 6 SEL2 NAME REG SEL2 SEL1 SEL0 CLK BIP/UNI RST X 1 = External clock, 0 = Internal clock. Defaulted to zero at power-up. 1 = Bipolar, 0 = Unipolar. Defaulted to zero at power-up (see the Unipolar/Bipolar section). 1 = No action, 0 = Resets the configuration register to default. Setup register remains unchanged. Don't care, can be set to 1 or 0. Three bits select the reference voltage and the state of AIN_/REF (Table 6). Default to 000 at power-up. BIT 5 SEL1 BIT 4 SEL0 BIT 3 CLK BIT 2 BIP/UNI BIT 1 RST BIT 0 (LSB) X
DESCRIPTION Register bit. 1 = Setup Byte, 0 = Configuration Byte (Table 2).
Single-Ended/Pseudo-Differential Input
The SGL/DIF bit of the configuration byte configures the MAX1036-MAX1039 analog input circuitry for singleended or pseudo-differential inputs (Table 2). In singleended mode (SGL/DIF = 1), the digital conversion results are the difference between the analog input selected by CS[3:0] and GND (Table 3). In pseudo-differential mode (SGL/DIF = 0), the digital conversion results are the difference between the `+' and the `-' analog inputs selected by CS[3:0] (Table 4). The `-' analog input signal must remain stable within 0.5LSB (0.1LSB for best results) with respect to GND during a conversion.
Digital Interface
The MAX1036-MAX1039 feature a 2-wire interface consisting of a serial data line (SDA) and a serial clock line (SCL). SDA and SCL facilitate bidirectional communication between the MAX1036-MAX1039 and the master at rates up to 1.7MHz. The MAX1036-MAX1039 are slaves that transmit and receive data. The master (typically a microcontroller) initiates data transfer on the bus and generates SCL to permit that transfer. SDA and SCL must be pulled high. This is typically done with pullup resistors (500 or greater) (see Typical Operating Circuit). Series resistors (RS) are optional. They protect the input architecture of the MAX1036-MAX1039 from high-voltage spikes on the bus lines and minimize crosstalk and undershoot of the bus signals. Bit Transfer One data bit is transferred during each SCL clock cycle. Nine clock cycles are required to transfer the data in or out of the MAX1036-MAX1039. The data on SDA must remain stable during the high period of the SCL clock pulse. Changes in SDA while SCL is high are control signals (see the START and STOP Conditions section). Both SDA and SCL idle high when the bus is not busy. START and STOP Conditions The master initiates a transmission with a START condition (S), a high-to-low transition on SDA with SCL high. The master terminates a transmission with a STOP condition (P), a low-to-high transition on SDA, while
11
Unipolar/Bipolar
When operating in pseudo-differential mode, the BIP/ UNI bit of the setup byte (Table 1) selects unipolar or bipolar operation. Unipolar mode sets the differential analog input range from zero to VREF. A negative differential analog input in unipolar mode causes the digital output code to be zero. Selecting bipolar mode sets the differential input range to VREF/2, with respect to the negative input. The digital output code is binary in unipolar mode and two's complement binary in bipolar mode (see the Transfer Functions section). In single-ended mode, the MAX1036-MAX1039 always operate in unipolar mode regardless of the BIP/UNI setting, and the analog inputs are internally referenced to GND with a full-scale input range from zero to VREF.
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2.7V to 5.5V, Low-Power, 4-/12-Channel 2-Wire Serial 8-Bit ADCs MAX1036-MAX1039
SCL is high (Figure 5). A repeated START condition (Sr) can be used in place of a STOP condition to leave the bus active and in its current timing mode (see the HSMode section). Acknowledge Bits Successful data transfers are acknowledged with an acknowledge bit (A) or a not-acknowledge bit (A). Both the master and the MAX1036-MAX1039 (slave) generate acknowledge bits. To generate an "acknowledge," the receiving device must pull SDA low before the rising edge of the acknowledge related clock pulse (ninth pulse) and keep it low during the high period of the clock pulse (Figure 6). To generate a "not acknowledge," the receiver allows SDA to be pulled high before the rising edge of the acknowledge related clock pulse and leaves it high during the high period of the clock pulse. Monitoring the acknowledge bits allows for detection of unsuccessful data transfers. An unsuccessful data transfer happens if a receiving device is busy or if a system fault has occurred. In the event of an unsuccessful data transfer, the bus master should reattempt communication at a later time. Slave Address A bus master initiates communication with a slave device by issuing a START condition followed by a slave address. When idle, the MAX1036-MAX1039 continuously wait for a START condition followed by their slave address. When the MAX1036-MAX1039 recognize their slave address, they are ready to accept or send data. The slave address has been factory programmed and is always 1100100 for the MAX1036/ MAX1037, and 1100101 for MAX1038/ MAX1039 (Figure 7). The least significant bit (LSB) of the address byte (R/W) determines whether the master is writing to or reading from the MAX1036-MAX1039 (R/W = zero selects a write condition. R/W = 1 selects a read condition). After receiving the address, the MAX1036- MAX1039 (slave) issue an acknowledge by pulling SDA low for one clock cycle. Bus Timing At power-up, the MAX1036-MAX1039 bus timing defaults to fast mode (F/S-mode) allowing conversion rates up to 44ksps. The MAX1036-MAX1039 must operate in high-speed mode (HS-mode) to achieve conversion rates up to 188ksps. Figure 1 shows the bus timing for the MAX1036-MAX1039's 2-wire interface. HS-Mode At power-up, the MAX1036-MAX1039 bus timing is set for F/S-mode. The master selects HS-mode by addressing all devices on the bus with the HS-mode master
12
S Sr P
SDA
SCL
Figure 5. START and STOP Conditions
S
NOT ACKNOWLEDGE
SDA ACKNOWLEDGE SCL 1 2 8 9
Figure 6. Acknowledge Bits
code 0000 1XXX (X = Don't care). After successfully receiving the HS-mode master code, the MAX1036- MAX1039 issues a not acknowledge, allowing SDA to be pulled high for one clock cycle (Figure 8). After the not acknowledge, the MAX1036-MAX1039 are in HS-mode. The master must then send a repeated START followed by a slave address to initiate HS-mode communication. If the master generates a STOP condition, the MAX1036-MAX1039 return to F/S-mode. Configuration/Setup Bytes (Write Cycle) Write cycles begin with the master issuing a START condition followed by 7 address bits (Figure 7) and 1 write bit (R/W = zero). If the address byte is successfully received, the MAX1036-MAX1039 (slave) issue an acknowledge. The master then writes to the slave. The slave recognizes the received byte as the setup byte (Table 1) if the most significant bit (MSB) is 1. If the MSB is zero, the slave recognizes that byte as the configuration byte (Table 2). The master can write either 1 or 2 bytes to the slave in any order (setup byte then configuration byte; configuration byte then setup byte; setup byte only; configuration byte only; Figure 9). If the slave receives bytes successfully, it issues an acknowledge. The master ends the write cycle by issuing a STOP condition or a repeated START condition. When operating in HS-mode, a STOP condition returns the bus to F/S-mode (see the HS-Mode section). Data Byte (Read Cycle) A read cycle must be initiated to obtain conversion results. Read cycles begin with the bus master issuing
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2.7V to 5.5V, Low-Power, 4-/12-Channel 2-Wire Serial 8-Bit ADCs MAX1036-MAX1039
DEVICE MAX1036/MAX1037 MAX1038/MAX1039 SLAVE ADDRESS 1100100 1100101
SLAVE ADDRESS S 1 1 0 0 1 0 0 R/W A
SDA
SCL
1
2
3
4
5
6
7
8
9
Figure 7. MAX1036/MAX1037 Slave Address Byte
HS-MODE MASTER CODE S 0 0 0 0 1 X X X A Sr
SDA
SCL
F/S-MODE
HS-MODE
Figure 8. F/S-Mode to HS-Mode Transfer
a START condition followed by 7 address bits and a read bit (R/W = 1). If the address byte is successfully received, the MAX1036-MAX1039 (slave) issue an acknowledge. The master then reads from the slave. After the master has received the results, it can issue an acknowledge if it wants to continue reading or a not acknowledge if it no longer wishes to read. If the MAX1036-MAX1039 receive a not acknowledge, they release SDA allowing the master to generate a STOP or repeated START. See the Clock Mode and Scan Mode sections for detailed information on how data is obtained and converted.
Clock Mode The clock mode determines the conversion clock, the acquisition time, and the conversion time. The clock mode also affects the scan mode. The state of the setup byte's CLK bit determines the clock mode (Table 1). At power-up, the MAX1036-MAX1039 default to internal clock mode (CLK = zero). Internal Clock When configured for internal clock mode (CLK = zero), the MAX1036-MAX1039 use their internal oscillator as the conversion clock. In internal clock mode, the MAX1036-MAX1039 begin tracking analog input on the ninth falling clock edge of a valid slave address byte. Two internal clock cycles later, the analog signal is acquired and the conversion begins. While tracking and converting the analog input signal, the MAX1036-MAX1039 hold SCL low (clock stretching). After the conversion completes, the results are stored
13
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2.7V to 5.5V, Low-Power, 4-/12-Channel 2-Wire Serial 8-Bit ADCs MAX1036-MAX1039
MASTER TO SLAVE SLAVE TO MASTER A. 1-BYTE WRITE CYCLE 1 S 7 SLAVE ADDRESS 11 8 1 1 NUMBER OF BITS
SETUP OR WA A P OR Sr CONFIGURATION BYTE
MSB DETERMINES WHETHER SETUP OR CONFIGURATION BYTE B. 2-BYTE WRITE CYCLE 1 S 7 SLAVE ADDRESS 11 8 1 A 8 1 1 NUMBER OF BITS
SETUP OR WA CONFIGURATION BYTE
SETUP OR A P OR Sr CONFIGURATION BYTE
MSB DETERMINES WHETHER SETUP OR CONFIGURATION BYTE
Figure 9. Write Cycle
in random access memory (RAM). If the scan mode is set for multiple conversions, they all happen in succession with each additional result being stored in RAM. The MAX1036/MAX1037 contain 8 bytes of RAM, and the MAX1038/MAX1039 contain 12 bytes of RAM. Once all conversions are complete, the MAX1036-MAX1039 release SCL, allowing it to be pulled high. The master can now clock the results out of the output shift register at a clock rate of up to 1.7MHz. SCL is stretched for a maximum acquisition and conversion time of 7.6s per channel (Figure 10). The device RAM contains all of the conversion results when the MAX1036-MAX1039 release SCL. The converted results are read back in a first-in-first-out (FIFO) sequence. If AIN_/REF is set to be a reference input or output (SEL1 = 1, Table 6), AIN_/REF is excluded from a multichannel scan. RAM contents can be read continuously. If reading continues past the last result stored in RAM, the pointer wraps around and points to the first result. Note that only the current conversion results are read from memory. The device must be addressed with a read command to obtain new conversion results. The internal clock mode's clock stretching quiets the SCL bus signal, reducing the system noise during conversion. Using the internal clock also frees the master (typically a microcontroller) from the burden of running the conversion clock.
External Clock When configured for external clock mode (CLK = 1), the MAX1036-MAX1039 use SCL as the conversion clock. In external clock mode, the MAX1036-MAX1039 begin tracking the analog input on the seventh falling clock edge of a valid slave address byte. One SCL clock cycle later, the analog signal is acquired and the conversion begins. Unlike internal clock mode, converted data is available immediately after the slave-address acknowledge bit. The device continuously converts input channels dictated by the scan mode until given a not acknowledge. There is no need to readdress the device with a read command to obtain new conversion results (Figure 11). The conversion must complete in 9ms or droop on the T/H capacitor degrades conversion results. Use internal clock mode if the SCL clock period exceeds 1ms. The MAX1036-MAX1039 must operate in external clock mode for conversion rates up to 188ksps. Scan Mode SCAN0 and SCAN1 of the configuration byte set the scan mode configuration. Table 5 shows the scanning configurations. If AIN_/REF is set to be a reference input or output (SEL1 = 1, Table 6), AIN_/REF is excluded from a multichannel scan.
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2.7V to 5.5V, Low-Power, 4-/12-Channel 2-Wire Serial 8-Bit ADCs MAX1036-MAX1039
Table 2. Configuration Byte Format
BIT 7 (MSB) REG BIT 7 6 5 4 3 2 1 0 BIT 6 SCAN1 NAME REG SCAN1 SCAN0 CS3 CS2 CS1 CS0 SGL/DIF 1 = single-ended, 0 = pseudo-differential (Tables 3, 4). Default to 1 at power-up (see the SingleEnded/Pseudo-Differential Input section). Channel select bits. Four bits select which analog input channels are to be used for conversion (Tables 3, 4). Default to 0000 at power-up. For MAX1036/MAX1037, CS3 and CS2 are internally set to 0. BIT 5 SCAN0 BIT 4 CS3 BIT 3 CS2 BIT 2 CS1 BIT 1 CS0 BIT 0 (LSB) SGL/DIF
DESCRIPTION Register bit. 1 = Setup Byte (Table 1), 0 = Configuration Byte. Scan select bits. Two bits select the scanning configuration (Table 5). Default to 00 at power-up.
Applications Information
Power-On Reset
The configuration and setup registers (Tables 1 and 2) default to a single-ended, unipolar, single-channel conversion on AIN0 using the internal clock with VDD as the reference and AIN_/REF configured as an analog input. The RAM contents are unknown after power-up. Automatic Shutdown SEL[2:0] of the setup byte (Tables 1 and 6) controls the state of the reference and AIN_/REF. If automatic shutdown is selected (SEL[2:0] = 100), shutdown occurs between conversions when the MAX1036-MAX1039 are idle. When operating in external clock mode, a STOP condition must be issued to place the devices in idle mode and benefit from automatic shutdown. A STOP condition is not necessary in internal clock mode to benefit from automatic shutdown because power-down occurs once all contents are written to memory (Figure 10). All analog circuitry is inactive in shutdown and supply current is less than 1A. The digital conversion results are maintained in RAM during shutdown and are available for access through the serial interface at any time prior to a STOP or repeated START condition. When idle, the MAX1036-MAX1039 wait for a START condition followed by their slave address (see the Slave Address section). Upon reading a valid address byte, the MAX1036-MAX1039 power up. The analog circuits do not require any wakeup time from shutdown, whether using external or internal reference.
Automatic shutdown results in dramatic power savings, particularly at slow conversion rates. For example, at a conversion rate of 10ksps, the average supply current for the MAX1036 is 8A and drops to 2A at 1ksps. At 0.1ksps the average supply current is just 1A (see Average Supply Current vs. Conversion Rate in the Typical Operating Characteristics section).
Reference Voltage
SEL[2:0] of the setup byte (Table 1) controls the reference and the AIN_/REF configuration (Table 6). When AIN_/REF is configured to be a reference input or reference output (SEL1 = 1), conversions on AIN_/REF appear as if AIN_/REF is connected to GND (see Note 2 of Tables 3 and 4). Internal Reference The internal reference is 4.096V for the MAX1036/ MAX1038 and 2.048V for the MAX1037/MAX1039. SEL1 of the setup byte controls whether AIN_/REF is used for an analog input or a reference (Table 6). When AIN_/REF is configured to be an internal reference output (SEL[2:1] = 11), decouple AIN_/REF to GND with a 0.01F capacitor. Due to the decoupling capacitor and the 675 reference source impedance, allow 80s for the reference to stabilize during initial power-up. Once powered up, the reference always remains on until reconfigured. The reference should not be used to supply current for external circuitry.
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15
2.7V to 5.5V, Low-Power, 4-/12-Channel 2-Wire Serial 8-Bit ADCs MAX1036-MAX1039
MASTER TO SLAVE SLAVE TO MASTER A. SINGLE CONVERSION WITH INTERNAL CLOCK 1 7 11 CLOCK STRETCH 8 RESULT 1 1 NUMBER OF BITS
S SLAVE ADDRESS R A
A P or Sr
tACQ
tCONV
B. SCAN MODE CONVERSIONS WITH INTERNAL CLOCK 1 7 1 1 CLOCK STRETCH CLOCK STRETCH 8 1 8 1 8 1 1 NUMBER OF BITS
S SLAVE ADDRESS R A tACQ1
RESULT 1 A RESULT 2 A
RESULT N A P OR Sr
tCONV1 NOTE: tACQ + tCONV 7.6s PER CHANNEL.
tACQ2 tCONV2
tACQN tCONVN
Figure 10. Internal Clock Mode Read Cycles
MASTER TO SLAVE SLAVE TO MASTER
A. SINGLE CONVERSION WITH EXTERNAL CLOCK 1 S 7 SLAVE ADDRESS 11 RA 8 RESULT 1 A 1 P OR Sr NUMBER OF BITS
tACQ
tCONV
B. SCAN MODE CONVERSIONS WITH EXTERNAL CLOCK 1 S 7 SLAVE ADDRESS tACQ1 tCONV1 11 RA 8 RESULT 1 1 A 8 RESULT 2 tACQ2 tCONV2 1 A 8 RESULT N tACQN tCONVN 1 1 NUMBER OF BITS
A P OR Sr
Figure 11. External Clock Mode Read Cycles
16
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2.7V to 5.5V, Low-Power, 4-/12-Channel 2-Wire Serial 8-Bit ADCs
Table 3. Channel Selection in Single-Ended Mode (SGL / DIF = 1)
CS31 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 CS21 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 CS1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 CS0 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 RESERVED RESERVED RESERVED RESERVED AIN0 + + + + + + + + + + + + AIN1 AIN2 AIN32 AIN4 AIN5 AIN6 AIN7 AIN8 AIN9 AIN10 AIN112 GND -
MAX1036-MAX1039
Note 1: For MAX1036/MAX1037, CS3 and CS2 are internally set to zero. Note 2: When SEL1 = 1, a single-ended read of AIN3/REF (MAX1036/MAX1037) or AIN11/REF (MAX1038/MAX1039) returns GND.
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17
2.7V to 5.5V, Low-Power, 4-/12-Channel 2-Wire Serial 8-Bit ADCs MAX1036-MAX1039
Table 4. Channel Selection in Pseudo-Differential Mode (SGL / DIF = 0)
CS31 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 CS21 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 CS1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 CS0 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 RESERVED RESERVED RESERVED RESERVED AIN0 + AIN1 + + + + + + + + + + + AIN2 AIN32 AIN4 AIN5 AIN6 AIN7 AIN8 AIN9 AIN10 AIN112
Note 1: For MAX1036/MAX1037, CS3 and CS2 are internally set to zero. Note 2: When SEL1 =1, a pseudo-differential read between AIN2 and AIN3/REF (MAX1036/MAX1037) or AIN10 and AIN11/REF (MAX1038/MAX1039) returns the difference between GND and AIN2 or AIN10, respectively. For example, a differential read of 1011 returns the negative difference between AIN10 and GND. Note 3: When scanning multiple channels (SCAN0 = 0), CS0 = 0 causes the even-numbered channel-select bits to be scanned, while CS0 = 1 causes the odd-numbered channel-select bits to be scanned. For example, if the MAX1038/MAX1039 SCAN[1:0] = 00 and CS[3:0] = 1010, a differential read returns AIN0-AIN1, AIN2-AIN3, AIN4-AIN5, AIN6-AIN7, AIN8-AIN9, and AIN10-AIN11. If the MAX1038/MAX1039 SCAN[1:0] = 00 and CS[3:0] = 1011, a differential read returns AIN1-AIN0, AIN3-AIN2, AIN5-AIN4, AIN7-AIN6, AIN9-8, and AIN11-AIN10.
18
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2.7V to 5.5V, Low-Power, 4-/12-Channel 2-Wire Serial 8-Bit ADCs MAX1036-MAX1039
Table 5. Scanning Configuration
SCAN1 0 0 SCAN0 0 1 SCANNING CONFIGURATION Scans up from AIN0 to the input selected by CS3-CS0 (default setting). Converts the input selected by CS3-CS0 eight times.* Scans up from AIN2 to the input selected by CS1 and CS0. When CS1 and CS0 are set for AIN0-AIN2, the scanning stops at AIN2 (MAX1036/MAX1037). 1 0 Scans up from AIN6 to the input selected by CS3-CS0. When CS3-CS0 is set for AIN0-AIN6 scanning stops at AIN6 (MAX1038/MAX1039). 1 1 Converts the channel selected by CS3-CS0.*
*When operating in external clock mode, there is no difference between SCAN[1:0] = 01 and SCAN[1:0] = 11 and converting continues until a not acknowledge occurs.
Table 6. Reference Voltage and AIN_/REF Format
SEL2 0 0 1 1 1 SEL1 0 1 0 0 1 SEL0 X X 0 1 X REFERENCE VOLTAGE VDD External reference Internal reference Internal reference Internal reference AIN_/REF Analog input Reference input Analog input Analog input Reference output INTERNAL REFERENCE STATE Always Off Always Off Auto Shutdown Always On Always On
X = Don't care.
External Reference The external reference can range from 1.0V to VDD. For maximum conversion accuracy, the reference must be able to deliver up to 30A and have an output impedance of 1k or less. If the reference has a higher output impedance or is noisy, bypass it to GND as close to AIN_/REF as possible with a 0.1F capacitor.
Transfer Functions
Output data coding for the MAX1036-MAX1039 is binary in unipolar mode and two's complement binary in bipolar mode with 1LSB = (VREF/2N) where N is the number of bits (8). Code transitions occur halfway between successive-integer LSB values. Figures 12 and 13 show the input/output (I/O) transfer functions for unipolar and bipolar operations, respectively.
necting 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) could influence the proper operation of the ADC's fast comparator. Bypass V DD to the star ground with a 0.1F capacitor located as close as possible to the MAX1036-MAX1039 power-supply pin. Minimize capacitor lead length for best supply-noise rejection, and add an attenuation resistor (5) if the power supply is extremely noisy.
Definitions
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 INL is measured using the endpoint method.
Layout, Grounding, and Bypassing
For best performance, use PC boards. Wire-wrap configurations are not recommended since the layout should ensure proper separation of analog 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 star point (Figure 14) con-
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19
2.7V to 5.5V, Low-Power, 4-/12-Channel 2-Wire Serial 8-Bit ADCs MAX1036-MAX1039
OUTPUT CODE REF 1...111 1...110 1...101 1...100 1LSB = VREF 256 OUTPUT CODE (TWO'S COMPLEMENT) REF 0...111 0...110 0...101 0...100 1LSB = VREF 256
0...001 0...000 1...111
0...011 0...010 0...001 0...000
0 1 2 3 252 253 254 255 256
1...011 1...010 1...001 1...000
-128 -127 -126 -125 -1 0 +1 +124 +125 +126 +127 +128
INPUT VOLTAGE (LSB)
'-' INPUT INPUT VOLTAGE (LSB)
Figure 12. Unipolar Transfer Function
Figure 13. Bipolar Transfer Function
Differential Nonlinearity
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.
VLOGIC = 3V/5V GND
SUPPLIES 3V/5V
Aperture Jitter
Aperture jitter (tAJ) is the sample-to-sample variation in the time between the samples.
R* = 5 0.1F
Aperture Delay
Aperture delay (t AD ) is the time between the rising edge of the sampling clock and the instant when an actual sample is taken.
VDD
GND
3V/5V
DGND
MAX1036 MAX1037 MAX1038 MAX1039
*OPTIONAL
DIGITAL CIRCUITRY
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 analogto-digital noise is caused by quantization error only and results directly from the ADC's resolution (N bits): SNR = (6.02 N + 1.76)dB
Figure 14. Power-Supply and Grounding Connections
20
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2.7V to 5.5V, Low-Power, 4-/12-Channel 2-Wire Serial 8-Bit ADCs
In reality, there are other noise sources besides quantization noise, including thermal noise, reference noise, clock jitter, etc. Therefore, 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.
Total Harmonic Distortion
Total harmonic distortion (THD) is the ratio of the RMS sum of the input signal's first five harmonics to the fundamental itself. This is expressed as: 2 2 2 2 THD = 20 x 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.
MAX1036-MAX1039
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)
Effective Number of Bits
Effective number of bits (ENOB) indicates the global accuracy of an ADC at a specific input frequency and sampling rate. An ideal ADC's error consists of quantization noise only. With an input range equal to the ADC's full-scale range, calculate the ENOB as follows: ENOB = (SINAD - 1.76) / 6.02
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
MAX1036/MAX1037 TRANSISTOR COUNT: 6283 MAX1038/MAX1039 TRANSISTOR COUNT: 7257 PROCESS: BiCMOS
Pin Configurations
TOP VIEW
Typical Operating Circuit
5V
AIN0 1 AIN1 2 AIN2 3
8 7
VDD GND SDA SCL ANALOG INPUTS AIN0 AIN1 AIN2 AIN3/REF
VDD MAX1036 MAX1037 MAX1038 MAX1039 GND 5V 5V RP *RS SDA SCL *RS
MAX1036 MAX1037
6 5
AIN3/REF 4
SOT23
AIN7 1 AIN6 2 AIN5 3 AIN4 4 AIN3 5 AIN2 6 AIN1 7 AIN0 8
16 AIN8 15 AIN9 14 AIN10 C SDA SCL
RP
MAX1038 MAX1039
13 AIN11/REF 12 VDD 11 GND 10 SDA 9 SCL *OPTIONAL
QSOP
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21
2.7V to 5.5V, Low-Power, 4-/12-Channel 2-Wire Serial 8-Bit ADCs MAX1036-MAX1039
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.)
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.
22 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 2002 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.
QSOP.EPS
SOT23, 8L.EPS

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