Maxim MAX1037 2.7v to 5.5v, low-power, 4-/12-channel 2-wire serial 8-bit adc Datasheet

19-2442; Rev 1; 10/02
2.7V to 5.5V, Low-Power, 4-/12-Channel
2-Wire Serial 8-Bit ADCs
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 350µA at
the maximum sampling rate of 188ksps. AutoShutdown™ powers down the devices between conversions reducing supply current to less than 1µA 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
(-40°C to +85°C). Refer to MAX1136–MAX1139 for 10-bit
devices and to the MAX1236–MAX1239 for 12-bit
devices.
Applications
Hand-Held Portable Applications
Medical Instruments
Battery-Powered Test Equipment
Solar-Powered Remote Systems
Received-Signal-Strength Indicators
System Supervision
Features
♦ High-Speed I2C-Compatible Serial Interface
400kHz Fast Mode
1.7MHz High-Speed Mode
♦ Single Supply
2.7V to 3.6V (MAX1037/MAX1039)
4.5V to 5.5V (MAX1036/MAX1038)
♦ Internal Reference
2.048V (MAX1037/MAX1039)
4.096V (MAX1036/MAX1038)
♦ External Reference: 1V to VDD
♦ Internal Clock
♦ 4-Channel Single-Ended or 2-Channel PseudoDifferential (MAX1036/MAX1037)
♦ 12-Channel Single-Ended or 6-Channel PseudoDifferential (MAX1038/MAX1039)
♦ Internal FIFO with Channel-Scan Mode
♦ Low Power
350µA at 188ksps
110µA at 75ksps
8µA at 10ksps
1µA in Power-Down Mode
♦ Software Configurable Unipolar/Bipolar
♦ Small Packages
8-Pin SOT23 (MAX1036/MAX1037)
16-Pin QSOP (MAX1038/MAX1039)
Pin Configurations and Typical Operating Circuit appear
at end of data sheet.
Ordering Information
PART
TUE
(LSB)
INPUT
CHANNELS
INTERNAL
REFERENCE (V)
8 SOT23-8
±2
4
4.096
AAJE
8 SOT23-8
±2
4
2.048
AAJG
-40°C to +85°C
16 QSOP
±1
12
4.096
—
-40°C to +85°C
16 QSOP
±1
12
2.048
—
TEMP RANGE
PIN-PACKAGE
MAX1036EKA-T
-40°C to +85°C
MAX1037EKA-T
-40°C to +85°C
MAX1038AEEE
MAX1039AEEE
TOP
MARK
AutoShutdown is a trademark of Maxim Integrated Products, Inc.
________________________________________________________________ Maxim Integrated Products
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
1
MAX1036–MAX1039
General Description
MAX1036–MAX1039
2.7V to 5.5V, Low-Power, 4-/12-Channel
2-Wire Serial 8-Bit ADCs
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 = +70°C)
8-Pin SOT23 (derate 7.1mW/°C above +70°C).............567mW
16-Pin QSOP (derate 8.3mW/°C above +70°C).........666.7mW
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-60°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(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 = +25°C.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
DC ACCURACY (Note 1)
Resolution
8
Bits
Relative Accuracy
INL
(Note 2)
±1
LSB
Differential Nonlinearity
DNL
No missing codes over temperature
±1
LSB
±1.5
LSB
Offset Error
Offset Error Temperature
Coefficient
3
Gain Error
±1
(Note 3)
±1
Gain Temperature Coefficient
Total Unadjusted Error
ppm/°C
TUE
LSB
ppm/°C
MAX1036/MAX1037
±0.5
±2
MAX1038A/MAX1039A
±0.5
±1
LSB
Channel-to-Channel Offset
Matching
±0.1
LSB
Channel-to-Channel Gain
Matching
±0.5
LSB
75
dB
Input Common-Mode Rejection
Ratio
CMRR
Pseudo-differential input mode
DYNAMIC PERFORMANCE (fIN(sine wave) = 25kHz, VIN = VREF(P-P), fSAMPLE = 188ksps, RIN = 100Ω)
Signal-to-Noise Plus Distortion
SINAD
Total Harmonic Distortion
THD
Spurious-Free Dynamic Range
SFDR
Up to the 5th harmonic
49
dB
-69
dB
69
dB
Channel-to-Channel Crosstalk
(Note 4)
75
dB
Full-Power Bandwidth
-3dB point
2.0
MHz
Full-Linear Bandwidth
SINAD > 49dB
200
kHz
CONVERSION RATE
Conversion Time (Note 5)
2
tCONV
Internal clock
External clock
6.1
4.7
_______________________________________________________________________________________
µs
2.7V to 5.5V, Low-Power, 4-/12-Channel
2-Wire Serial 8-Bit ADCs
(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 = +25°C.)
PARAMETER
Throughput Rate
SYMBOL
fSAMPLE
CONDITIONS
MIN
TYP
Internal clock, SCAN[1:0] = 01
(MAX1036/MAX1037)
76
Internal clock, SCAN[1:0] = 00
CS[3:0] = 1011 (MAX1038/MAX1039)
77
External clock
588
Internal Clock Frequency
ksps
ns
2.25
tAD
UNITS
188
Track/Hold Acquisition Time
Aperture Delay
MAX
External clock, fast mode
45
External clock, high-speed mode
30
MHz
ns
ANALOG INPUT (AIN0–AIN11)
Unipolar
Input Voltage Range, Single
Ended and Differential (Note 6)
VREF
±VREF / 2
On/off-leakage current, VAIN_= 0 or VDD,
no clock, fSCL = 0
Input Multiplexer Leakage Current
Input Capacitance
0
Bipolar
±0.01
CIN
±1
18
V
µA
pF
INTERNAL REFERENCE (Note 7)
Reference Voltage
VREF
Reference Temperature
Coefficient
TA = +25°C
MAX1037/MAX1039
1.925
2.048
2.171
MAX1036/MAX1038
3.850
4.096
4.342
TCREF
120
Reference Short-Circuit Current
ppm/°C
10
Reference Source Impedance
(Note 8)
V
mA
Ω
675
EXTERNAL REFERENCE
Reference Input Voltage Range
VREF
(Note 9)
REF Input Current
IREF
fSAMPLE = 188ksps
1.0
14
VDD
V
30
µA
DIGITAL INPUTS/OUTPUTS (SCL, SDA)
Input High Voltage
VIH
Input Low Voltage
VIL
Input Hysteresis
0.7 x VDD
VHYST
Input Current
IIN
Input Capacitance
CIN
Output Low Voltage
VOL
V
0.3 x VDD
0.1 x VDD
V
±10
VIN = 0 to VDD
15
ISINK = 3mA
V
µA
pF
0.4
V
_______________________________________________________________________________________
3
MAX1036–MAX1039
ELECTRICAL CHARACTERISTICS (continued)
MAX1036–MAX1039
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 = +25°C.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
POWER REQUIREMENTS
Supply Voltage (Note 10)
Supply Current
VDD
IDD
MAX1037/MAX1039
2.7
3.6
MAX1036/MAX1038
4.5
5.5
fSAMPLE =
188ksps
Internal REF, external clock
350
External REF, external clock
250
fSAMPLE =
75ksps
External REF, external clock
110
External REF, internal clock
150
fSAMPLE =
10ksps
External REF, external clock
8
External REF, internal clock
10
fSAMPLE =
1ksps
External REF, external clock
2
External REF, internal clock
2.5
Power-down
Power-Supply Rejection Ratio
PSRR
(Note 11)
V
650
µA
1
10
±0.25
±1
LSB/V
400
kHz
TIMING CHARACTERISTICS FOR 2-WIRE FAST MODE (Figures 1A and 2)
Serial Clock Frequency
fSCL
Bus Free Time Between a STOP
and a START Condition
tBUF
1.3
µs
Hold Time for Start Condition
tHD, STA
0.6
µs
Low Period of the SCL Clock
tLOW
1.3
µs
High Period of the SCL Clock
tHIGH
0.6
µs
Setup Time for a Repeated START
Condition (Sr)
tSU, STA
0.6
µs
Data Hold Time
tHD, DAT
Data Setup Time
tSU, DAT
(Note 12)
0
150
100
ns
ns
Rise Time of Both SDA and SCL
Signals, Receiving
tR
(Note 13)
20 + 0.1CB
300
ns
Fall Time of SDA Transmitting
tF
(Note 13)
20 + 0.1CB
300
ns
Setup Time for STOP Condition
tSU, STO
0.6
µs
Capacitive Load for Each Bus Line
CB
400
pF
Pulse Width of Spike Suppressed
tSP
50
ns
1.7
MHz
TIMING CHARACTERISTICS FOR 2-WIRE HIGH-SPEED MODE (Figures 1B and 2)
Serial Clock Frequency
Hold Time (Repeated) Start
Condition
fSCLH
(Note 14)
tHD, STA
160
ns
Low Period of the SCL Clock
tLOW
320
ns
High Period of the SCL Clock
tHIGH
120
ns
4
_______________________________________________________________________________________
2.7V to 5.5V, Low-Power, 4-/12-Channel
2-Wire Serial 8-Bit ADCs
(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 = +25°C.)
PARAMETER
SYMBOL
Setup Time for a Repeated START
Condition (Sr)
tSU, STA
Data Hold Time
tHD, DAT
Data Setup Time
tSU, DAT
CONDITIONS
MIN
TYP
MAX
160
(Note 12)
0
UNITS
ns
150
10
ns
ns
Rise Time of SCL Signal
(Current Source Enabled)
tRCL
(Note 13)
20
80
ns
Rise Time of SCL Signal After
Acknowledge Bit
tRCL1
(Note 13)
20
160
ns
Fall Time of SCL Signal
tFCL
(Note 13)
20
80
ns
Rise Time of SDA Signal
tRDA
(Note 13)
20
160
ns
Fall Time of SDA Signal
tFDA
(Note 13)
20
160
Setup Time for STOP Condition
tSU, STO
Capacitive Load for Each Bus Line
CB
Pulse Width of Spike Suppressed
tSP
160
0
ns
ns
400
pF
10
ns
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 0.01µF capacitor.
Note 8: The switch connecting the reference buffer to AIN_/REF has a typical on-resistance of 675Ω.
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:
N
[VFS (3.3V) − VFS (2.7V)] × V2REF
3.3V − 2.7V
, for the MAX1037/MAX1039 where N is the number of bits (8) and VREF = 2.048V.
Power-supply rejection ratio is measured as:
N
[VFS (5.5V) − VFS (4.5V)] × V2REF
5.5V − 4.5V
, 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 +25°C with CB = 400pF.
Note 14: fSCLH must meet the minimum clock low time plus the rise/fall times.
_______________________________________________________________________________________
5
MAX1036–MAX1039
ELECTRICAL CHARACTERISTICS (continued)
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 = +25°C, unless otherwise noted.)
SUPPLY CURRENT
vs. TEMPERATURE
400
A
SDA = SCL = VDD
4
INTERNAL 4.096VREF
350
IDD (µA)
B
300
300
INTERNAL 2.048VREF
C
250
IDD (µA)
350
IDD (µA)
5
MAX1036 toc02
A) INTERNAL 4.096VREF
B) INTERNAL 2.048VREF
C) EXTERNAL 4.096VREF
D) EXTERNAL 2.048VREF
400
450
MAX1036 toc01
450
SHUTDOWN SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX1036 toc03
SUPPLY CURRENT
vs. VOLTAGE
3
2
EXTERNAL 4.096VREF
250
D
200
200
150
3.0
3.5
4.0
4.5
5.0
0
-40
-15
10
35
60
85
2.5
3.5
4.0
4.5
5.0
5.5
VDD (V)
SHUTDOWN SUPPLY CURRENT
vs. TEMPERATURE
AVERAGE SUPPLY CURRENT vs.
CONVERSION RATE (INTERNAL CLOCK)
AVERAGE SUPPLY CURRENT VS.
CONVERSION RATE (EXTERNAL CLOCK)
350
300
VDD = 5V
A
500
A) INTERNAL REF ALWAYS ON
B) INTERNAL REF AUTOSHUTDOWN
C) EXTERNAL REF
A
450
400
250
B
AVERAGE IDD (µA)
AVERAGE IDD (µA)
3
A) INTERNAL REF ALWAYS ON
B) INTERNAL REF AUTOSHUTDOWN
C) EXTERNAL REF
MAX1036 toc05
SDA = SCL = VDD
200
C
150
100
MAX1036 toc06
TEMPERATURE (°C)
2
350
300
B
250
200
C
150
100
1
50
INTERNAL CLOCK MODE
fSCL = 1.7MHz
VDD = 3.3V
-15
10
35
60
0
0
85
10
20
30
40
50
60
TEMPERATURE (°C)
CONVERSION RATE (ksps)
NORMALIZED 4.096V REFERENCE VOLTAGE
vs. SUPPLY VOLTAGE
INTERNAL 4.096V REFERENCE VOLTAGE
vs. TEMPERATURE
1.015
1.0000
0.9975
1.0050
1.005
1.000
0.995
1.0025
1.0000
0.9975
0.9950
0.990
0.9950
0.9925
0.985
0.9925
0.9900
0.980
4.00
4.25
4.50
4.75
VDD (V)
5.00
5.25
5.50
200
1.0075
VREF NORMALIZED
1.0025
150
1.0100
1.010
VREF NORMALIZED
1.0050
100
INTERNAL 2.048V REFERENCE VOLTAGE
vs. SUPPLY VOLTAGE
MAX1036 toc08
1.0075
50
CONVERSION RATE (ksps)
1.020
MAX1036 toc7
1.0100
0
MAX1036 toc09
-40
EXTERNAL CLOCK MODE
fSCL = 1.7MHz
50
0
0
6
3.0
VDD (V)
4
IDD (µA)
5.5
MAX1036 toc04
5
1
EXTERNAL 2.048VREF
150
2.5
VREF NORMALIZED
MAX1036–MAX1039
2.7V to 5.5V, Low-Power, 4-/12-Channel
2-Wire Serial 8-Bit ADCs
0.9900
-40
-15
10
35
TEMPERATURE (°C)
60
85
2.5
3.0
3.5
4.0
VDD (V)
_______________________________________________________________________________________
4.5
5.0
5.5
2.7V to 5.5V, Low-Power, 4-/12-Channel
2-Wire Serial 8-Bit ADCs
DIFFERENTIAL NONLINEARITY
vs. DIGITAL CODE
0.4
0.3
DNL (LSB)
1.005
1.000
0.995
0.3
0.2
0.2
0.1
0.1
0
-0.1
0
-0.1
-0.2
-0.2
-0.3
-0.3
0.985
-0.4
-0.4
0.980
-0.5
0.990
35
60
85
-0.5
0
50
TEMPERATURE (°C)
100
150
200
250
300
0
50
DIGITAL OUTPUT CODE
1.0
MAX1036 toc13
fSAMPLE = 188ksps
fIN = 25kHz
-40
-60
-80
VREF = 2.048V
0.9
0.8
OFFSET ERROR (LSB)
-20
150
200
250
300
OFFSET ERROR vs. SUPPLY VOLTAGE
FFT PLOT
0
100
DIGITAL OUTPUT CODE
MAX1036 toc14
10
0.7
0.6
0.5
0.4
0.3
0.2
-100
0.1
-120
0
40k
60k
80k
2.5
100k
3.0
3.5
FREQUENCY (Hz)
4.5
5.0
5.5
GAIN ERROR vs. SUPPLY VOLTAGE
OFFSET ERROR vs. TEMPERATURE
1.0
0.9
4.0
VDD (V)
0
VDD = 3.3V
VREF = 2.048V
0.8
0.6
0.5
0.4
0.3
-0.02
-0.03
-0.04
-0.05
-0.06
-0.07
0.2
-0.08
0.1
-0.09
0
VREF = 2.048V
-0.01
GAIN ERROR (LSB)
0.7
MAX1036 toc16
20k
0
MAX1036 toc15
-15
AMPLITUDE (dBc)
-40
OFFSET ERROR (LSB)
VREF NORMALIZED
1.010
0.4
INL (LSB)
1.015
0.5
MAX1036 toc11
0.5
MAX1036 toc10
1.020
INTEGRAL NONLINEARITY
vs. DIGITAL CODE
MAX1036 toc12
INTERNAL 2.048V REFERENCE VOLTAGE
vs. TEMPERATURE
-0.1
-40
-15
10
35
TEMPERATURE (°C)
60
85
2.5
3.0
3.5
4.0
4.5
5.0
5.5
VDD (V)
_______________________________________________________________________________________
7
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 = +25°C, unless otherwise noted.)
2.7V to 5.5V, Low-Power, 4-/12-Channel
2-Wire Serial 8-Bit ADCs
MAX1036–MAX1039
Pin Description
PIN
MAX1036/
MAX1037
MAX1038/
MAX1039
NAME
FUNCTION
1, 2, 3
8, 7, 6
AIN0–AIN2
—
5, 4, 3, 2, 1
AIN3–AIN7
—
16, 15, 14
AIN8–AIN10
4
—
AIN3/REF
Analog Input 3/Reference Input or Output. Selected in the setup
register.
—
13
AIN11/REF
Analog Input 11/Reference Input or Output. Selected in the setup
register.
Analog Inputs
5
9
SCL
Clock Input
6
10
SDA
Data Input/Output
7
11
GND
Ground
8
12
VDD
Positive Supply. Bypass to GND with a 0.1µF capacitor.
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 350µA 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.
8
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 0.1µF 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 1.5kΩ
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
_______________________________________________________________________________________
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
tHD.DAT
tHD.STA
tLOW
tBUF
tSU.STA
tSU.STO
SCL
tHD.STA
tHIGH
tR
tF
S
A
Sr
P
S
B. HS-MODE I2C SERIAL INTERFACE TIMING
tRDA
tFDA
SDA
tSU.DAT
tHD.DAT
tBUF
tHD.STA
tLOW
tSU.STO
tSU.STA
SCL
tHD.STA
tHIGH
tRCL
tFCL
tRCL1
S
Sr
A
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 = 2.5kΩ, and CIN = 18pF. tACQ is 1/fSCL for external
VDD
IOL = 3mA
VOUT
SDA
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.
_______________________________________________________________________________________
9
MAX1036–MAX1039
2.7V to 5.5V, Low-Power, 4-/12-Channel
2-Wire Serial 8-Bit ADCs
SDA
SCL
INPUT SHIFT REGISTER
VDD
SETUP REGISTER
GND
CONTROL
LOGIC
INTERNAL
OSCILLATOR
CONFIGURATION REGISTER
AIN0
AIN1
AIN2
AIN3
AIN4
AIN5
AIN6
AIN7
AIN8
AIN9
AIN10
AIN11/REF
T/H
ANALOG
INPUT
MUX
OUTPUT SHIFT
REGISTER AND
12-BYTE RAM
8-BIT
ADC
REF
REFERENCE
4.096V (MAX1038)
2.048V (MAX1039)
MAX1038
MAX1039
Figure 3. MAX1038/MAX1039 Simplified Functional Diagram
ANALOG INPUT MUX
REF
CT/H
AIN2
AIN3/REF
GND
HOLD
HOLD
SINGLE ENDED
CAPACITIVE
DAC
TRACK
TRACK
AIN1
DIFFERENTIAL
AIN0
MAX1036
MAX1037
Figure 4. Equivalent Input Circuit
Analog Input Bandwidth
Analog Input Range and Protection
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.
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.
10
______________________________________________________________________________________
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)
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
(LSB)
REG
SEL2
SEL1
SEL0
CLK
BIP/UNI
RST
X
BIT
NAME
7
REG
6
SEL2
5
SEL1
4
SEL0
3
CLK
2
BIP/UNI
1
RST
0
X
DESCRIPTION
Register bit. 1 = Setup Byte, 0 = Configuration Byte (Table 2).
Three bits select the reference voltage and the state of AIN_/REF (Table 6). Default to 000 at
power-up.
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.
Single-Ended/Pseudo-Differential Input
Digital Interface
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.
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.
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.
SDA and SCL must be pulled high. This is typically
done with pullup resistors (500Ω 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
MAX1036–MAX1039
2.7V to 5.5V, Low-Power, 4-/12-Channel
2-Wire Serial 8-Bit ADCs
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
P
Sr
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
______________________________________________________________________________________
2.7V to 5.5V, Low-Power, 4-/12-Channel
2-Wire Serial 8-Bit ADCs
SLAVE ADDRESS
MAX1036/MAX1037
1100100
MAX1038/MAX1039
1100101
MAX1036–MAX1039
DEVICE
SLAVE ADDRESS
S
1
1
0
0
1
0
0
R/W
A
SDA
1
SCL
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
MAX1036–MAX1039
2.7V to 5.5V, Low-Power, 4-/12-Channel
2-Wire Serial 8-Bit ADCs
MASTER TO SLAVE
SLAVE TO MASTER
A. 1-BYTE WRITE CYCLE
1
S
7
1 1
SLAVE ADDRESS
8
1
1
NUMBER OF BITS
SETUP OR
W A
A P OR Sr
CONFIGURATION BYTE
MSB DETERMINES WHETHER
SETUP OR CONFIGURATION BYTE
B. 2-BYTE WRITE CYCLE
1
S
7
1 1
SLAVE ADDRESS
8
SETUP OR
W A
CONFIGURATION BYTE
1
A
8
1
1
NUMBER OF BITS
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 7.6µs 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.
14
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.
______________________________________________________________________________________
2.7V to 5.5V, Low-Power, 4-/12-Channel
2-Wire Serial 8-Bit ADCs
BIT 7
(MSB)
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
(LSB)
REG
SCAN1
SCAN0
CS3
CS2
CS1
CS0
SGL/DIF
BIT
NAME
7
REG
6
SCAN1
5
SCAN0
4
CS3
3
CS2
2
CS1
1
CS0
0
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.
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.
1 = single-ended, 0 = pseudo-differential (Tables 3, 4). Default to 1 at power-up (see the SingleEnded/Pseudo-Differential Input section).
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 1µA. 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 8µA and drops to 2µA at 1ksps.
At 0.1ksps the average supply current is just 1µA (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
0.01µF capacitor. Due to the decoupling capacitor and
the 675Ω reference source impedance, allow 80µs 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.
______________________________________________________________________________________
15
MAX1036–MAX1039
Table 2. Configuration Byte Format
MAX1036–MAX1039
2.7V to 5.5V, Low-Power, 4-/12-Channel
2-Wire Serial 8-Bit ADCs
MASTER TO SLAVE
SLAVE TO MASTER
A. SINGLE CONVERSION WITH INTERNAL CLOCK
1
7
8
1 1
S SLAVE ADDRESS R A
RESULT
CLOCK STRETCH
tACQ
1
1
NUMBER OF BITS
A P or Sr
tCONV
B. SCAN MODE CONVERSIONS WITH INTERNAL CLOCK
7
1
1
1
8
S SLAVE ADDRESS R A
CLOCK STRETCH
CLOCK STRETCH
tACQ1
tACQ2
tCONV2
tCONV1
1
8
1
8
RESULT 1 A RESULT 2 A
1
1
NUMBER OF BITS
RESULT N A P OR Sr
tACQN
tCONVN
NOTE: tACQ + tCONV ≤ 7.6µs PER CHANNEL.
Figure 10. Internal Clock Mode Read Cycles
MASTER TO SLAVE
SLAVE TO MASTER
A. SINGLE CONVERSION WITH EXTERNAL CLOCK
1
7
1 1
8
1
1
S
SLAVE ADDRESS
R A
RESULT
A
P OR Sr
tACQ
NUMBER OF BITS
tCONV
B. SCAN MODE CONVERSIONS WITH EXTERNAL CLOCK
1
S
7
1 1
SLAVE ADDRESS
R A
8
1
RESULT 1
A
tACQ1
tCONV1
8
1
RESULT 2
A
tACQ2
tCONV2
8
RESULT N
1
1
NUMBER OF BITS
A P OR Sr
tACQN
tCONVN
Figure 11. External Clock Mode Read Cycles
16
______________________________________________________________________________________
2.7V to 5.5V, Low-Power, 4-/12-Channel
2-Wire Serial 8-Bit ADCs
CS31
CS21
CS1
CS0
AIN0
0
0
0
0
+
0
0
0
1
0
0
1
0
0
0
1
1
0
1
0
0
0
1
0
1
0
1
1
0
0
1
1
1
1
0
0
0
1
0
0
1
1
0
1
0
1
0
1
1
1
1
0
0
RESERVED
1
1
0
1
RESERVED
1
1
1
0
RESERVED
1
1
1
1
RESERVED
AIN1
AIN2
AIN32
AIN4
AIN5
AIN6
AIN7
AIN8
AIN9
AIN10 AIN112 GND
-
+
+
+
+
+
+
+
+
+
+
+
-
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.
______________________________________________________________________________________
17
MAX1036–MAX1039
Table 3. Channel Selection in Single-Ended Mode (SGL / DIF = 1)
MAX1036–MAX1039
2.7V to 5.5V, Low-Power, 4-/12-Channel
2-Wire Serial 8-Bit ADCs
Table 4. Channel Selection in Pseudo-Differential Mode (SGL / DIF = 0)
CS31
CS21
CS1
CS0
AIN0
AIN1
0
0
0
0
+
-
0
0
0
1
-
+
0
0
1
0
+
-
0
0
1
1
-
+
0
1
0
0
+
-
0
1
0
1
-
+
0
1
1
0
1
1
0
1
AIN2
AIN32
AIN4
AIN5
AIN8
AIN9
AIN10 AIN112
AIN6
AIN7
0
+
-
1
1
-
+
0
0
+
-
0
0
1
-
+
1
0
1
0
+
-
1
0
1
1
-
+
1
1
0
0
RESERVED
1
1
0
1
RESERVED
1
1
1
0
RESERVED
1
1
1
1
RESERVED
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
______________________________________________________________________________________
2.7V to 5.5V, Low-Power, 4-/12-Channel
2-Wire Serial 8-Bit ADCs
SCAN1
SCAN0
SCANNING CONFIGURATION
0
0
Scans up from AIN0 to the input selected by CS3–CS0 (default setting).
0
1
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
REFERENCE VOLTAGE
AIN_/REF
INTERNAL REFERENCE
STATE
SEL2
SEL1
SEL0
0
0
X
VDD
Analog input
Always Off
0
1
X
External reference
Reference input
Always Off
1
0
0
Internal reference
Analog input
Auto Shutdown
1
0
1
Internal reference
Analog input
Always On
1
1
X
Internal reference
Reference output
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 30µA and have an output impedance of 1kΩ 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 0.1µF 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.
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-
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
0.1µF 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 (5Ω) 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.
______________________________________________________________________________________
19
MAX1036–MAX1039
Table 5. Scanning Configuration
MAX1036–MAX1039
2.7V to 5.5V, Low-Power, 4-/12-Channel
2-Wire Serial 8-Bit ADCs
OUTPUT CODE
1LSB =
OUTPUT CODE
(TWO'S COMPLEMENT)
VREF
256
1LSB =
VREF
256
REF
0...111
0...110
0...101
0...100
REF
1...111
1...110
1...101
1...100
0...001
0...000
1...111
1...011
1...010
1...001
1...000
0...011
0...010
0...001
0...000
0
1
2
3
252 253 254 255 256
-128 -127 -126 -125
-1
0
+1
+124 +125 +126 +127 +128
'-' INPUT
INPUT VOLTAGE (LSB)
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.
SUPPLIES
3V/5V
VLOGIC = 3V/5V
GND
Aperture Jitter
Aperture jitter (tAJ) is the sample-to-sample variation in
the time between the samples.
R* = 5Ω
Aperture Delay
0.1µF
VDD
GND
MAX1036
MAX1037
MAX1038
MAX1039
3V/5V
DGND
DIGITAL
CIRCUITRY
*OPTIONAL
Figure 14. Power-Supply and Grounding Connections
20
Aperture delay (t AD ) is the time between the rising
edge of the sampling clock and the instant when an
actual sample is taken.
Signal-to-Noise Ratio
For a waveform perfectly reconstructed from digital samples, signal-to-noise ratio (SNR) is the ratio of full-scale
analog input (RMS value) to the RMS quantization error
(residual error). The ideal, theoretical minimum 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
______________________________________________________________________________________
2.7V to 5.5V, Low-Power, 4-/12-Channel
2-Wire Serial 8-Bit ADCs
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
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 × log   V2 + V3 + V4 + V5  / V1 

 



where V1 is the fundamental amplitude, and V2 through
V5 are the amplitudes of the 2nd- through 5th-order
harmonics.
Spurious-Free Dynamic Range
Spurious-free dynamic range (SFDR) is the ratio of RMS
amplitude of the fundamental (maximum signal component) to the RMS value of the next-largest distortion
component.
Chip Information
MAX1036/MAX1037 TRANSISTOR COUNT: 6283
MAX1038/MAX1039 TRANSISTOR COUNT: 7257
PROCESS: BiCMOS
Pin Configurations
Typical Operating Circuit
5V
TOP VIEW
AIN0 1
8
VDD
AIN1 2
7
GND
6
SDA
5
SCL
AIN2
3
MAX1036
MAX1037
AIN3/REF 4
VDD
ANALOG
INPUTS
AIN0
AIN1
AIN2
AIN3/REF
*RS
MAX1036
MAX1037
MAX1038
MAX1039
SDA
SCL
*RS
GND
5V
SOT23
RP
5V
AIN7 1
16 AIN8
AIN6 2
15 AIN9
AIN5 3
14 AIN10
AIN4 4
AIN3 5
MAX1038
MAX1039
RP
µC
SDA
SCL
13 AIN11/REF
12 VDD
AIN2 6
11 GND
AIN1 7
10 SDA
AIN0 8
9
*OPTIONAL
SCL
QSOP
______________________________________________________________________________________
21
MAX1036–MAX1039
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.
Package Information
SOT23, 8L.EPS
(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.)
QSOP.EPS
MAX1036–MAX1039
2.7V to 5.5V, Low-Power, 4-/12-Channel
2-Wire Serial 8-Bit ADCs
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
© 2002 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.