18-Bit, Single-Channel, Ultra-Low-Power, Delta-
Sigma ADCs with Programmable Gain and GPIO
MAX11209/MAX11211
19-5473; Rev 0; 8/10
General Description
The MAX11209/MAX11211 are ultra-low-power (< 300FA
active current), high-resolution, serial-output ADCs.
These devices provide the highest resolution per unit
power in the industry, and are optimized for applications
that require very high dynamic range with low power,
such as sensors on a 4mA to 20mA industrial control
loop. Optional input buffers provide isolation of the sig-
nal inputs from the switched capacitor sampling network
allowing these converters to be used with high-imped-
ance sources without compromising available dynamic
range or linearity. The devices provide a high-accuracy
internal oscillator that requires no external components.
When used with the specified data rates, the internal
digital filter provides more than 100dB rejection of 50Hz
or 60Hz line noise. The devices are configurable using
the SPI™ interface and include four GPIOs that can be
used for external mux control. The MAX11209 includes
digital programmable gain of 1 to 128.
The MAX11209/MAX11211 operate over the -40NC to
+85NC temperature range, and are available in a 16-pin
QSOP package.
Applications
Sensor Measurement (Temperature and
Pressure)
Portable Instrumentation
Battery Applications
Weigh Scales
Features
S 18-Bit Noise-Free Resolution
S 570nVRMS Noise at 10sps, ±3.6VFS Input
S 3ppm INL (typ), 15ppm (max)
S No Missing Codes
S Ultra-Low Power Dissipation
Operating-Mode Current Drain < 300µA (max)
Sleep-Mode Current Drain < 0.4µA
S Programmable Gain (1 to 128) (MAX11209)
S Four SPI-Controlled GPIOs for External Mux
Control
S 2.7V to 3.6V Analog Supply Voltage Range
S 1.7V to 3.6V Digital and I/O Supply Voltage Range
S Fully Differential Signal and Reference Inputs
S High-Impedance Inputs
Optional Input Buffers on Both Signal and
Reference Inputs
S > 100dB (min) 50Hz/60Hz Rejection
S SPI-, QSPI™-, MICROWIRE™-Compatible Serial
Interface
S On-Demand Offset and Gain Self-Calibration and
System Calibration
S User-Programmable Offset and Gain Registers
S -40°C to +85°C Operating Temperature Range
S ±2kV ESD Protection
S Lead(Pb)-Free and RoHS-Compliant QSOP
Package
SPI and QSPI are trademarks of Motorola, Inc.
MICROWIRE is a trademark of National Semiconductor Corp.
Ordering Information
+Denotes a lead(Pb)-free/RoHS-compliant package.
Selector Guide
PART TEMP RANGE PIN-PACKAGE
MAX11209EEE+ -40°C to +85°C16 QSOP
MAX11211EEE+ -40°C to +85°C16 QSOP
RESOLUTION
(BITS)
4-WIRE SPI, 16-PIN QSOP,
PROGRAMMABLE GAIN
4-WIRE SPI,
16-PIN QSOP
2-WIRE SERIAL,
10-PIN µMAX
24 MAX11210 MAX11200 MAX11201 (with buffers)
MAX11202 (without buffers)
20 MAX11206 MAX11207 MAX11208
18 MAX11209 MAX11211 MAX11212
16 MAX11213 MAX11203 MAX11205
For pricing, delivery, and ordering information, please contact Maxim Direct
at 1-888-629-4642, or visit Maxim’s website at www.maximintegrated.com.
2 Maxim Integrated
18-Bit, Single-Channel, Ultra-Low-Power, Delta-
Sigma ADCs with Programmable Gain and GPIO
MAX11209/MAX11211
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.
Any Pin to GND ....................................................-0.3V to +3.9V
AVDD to GND .......................................................-0.3V to +3.9V
DVDD to GND ......................................................-0.3V to +3.9V
Analog Inputs (AINP, AINN, REFP, REFN)
to GND ............................................. -0.3V to (VAVDD + 0.3V)
Digital Inputs and Digital Outputs
to GND ............................................. -0.3V to (VDVDD + 0.3V)
ESDHB (AVDD, AINP, AINN, REFP, REFN, DVDD, CLK, CS,
SCLK, DIN, RDY/DOUT, GND, GPIO_) ........... Q2kV (Note 1)
Continuous Power Dissipation (TA = +70NC)
16-Pin QSOP (derate 8.3mW/NC above +70NC) ..........667mW
Operating Temperature Range .......................... -40NC to +85NC
Junction Temperature .....................................................+150NC
Storage Temperature Range ............................ -55NC to +150NC
Lead Temperature (soldering, 10s) ................................+300NC
Soldering Temperature (reflow) ......................................+260NC
ELECTRICAL CHARACTERISTICS
(VAVDD = +3.6V, VDVDD = +1.7V, VREFP - VREFN = VAVDD; internal clock, single-cycle mode (SCYCLE = 1), TA = TMIN to TMAX,
unless otherwise noted. Typical values are at TA = +25NC under normal conditions, unless otherwise noted.)
ABSOLUTE MAXIMUM RATINGS
Note 1: Human Body Model to specification MIL-STD-883 Method 3015.7.
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
STATIC PERFORMANCE
Noise-Free Resolution (Notes 2, 3) NFR 120sps 18 Bits
10sps 18
Noise (Notes 2, 3) VN120sps 2.1 FVRMS
10sps 0.55
Integral Nonlinearity INL At 10sps (Note 4) -15 +15 ppmFSR
Zero Error After self and system calibration,
VREFP - VREFN = 2.5V -15 +15 ppmFSR
Zero Drift 50 nV/NC
Full-Scale Error After self and system calibration,
VREFP - VREFN = 2.5V (Note 5) -20 +20 ppmFSR
Full-Scale Error Drift 0.05 ppmFSR/
NC
Power-Supply Rejection AVDD DC rejection 70 80 dB
DVDD DC rejection 90 100
ANALOG INPUTS/REFERENCE INPUTS
Common-Mode Rejection CMR
DC rejection 90 123
dB50Hz/60Hz rejection at 120sps 90
50Hz/60Hz rejection at 1sps to 15sps 144
Normal-Mode 50Hz Rejection NMR50 LINEF = 1, for 1sps to 15sps (Notes 6, 7) 100 144 dB
Normal-Mode 60Hz Rejection NMR60 LINEF = 0, for 1sps to 15sps (Notes 6, 7) 100 144 dB
Common-Mode Voltage Range AIN buffers disabled VGND VAVDD V
3Maxim Integrated
18-Bit, Single-Channel, Ultra-Low-Power, Delta-
Sigma ADCs with Programmable Gain and GPIO
MAX11209/MAX11211
ELECTRICAL CHARACTERISTICS (continued)
(VAVDD = +3.6V, VDVDD = +1.7V, VREFP - VREFN = VAVDD; internal clock, single-cycle mode (SCYCLE = 1), TA = TMIN to TMAX,
unless otherwise noted. Typical values are at TA = +25NC under normal conditions, unless otherwise noted.)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Absolute Input Voltage
Low input voltage
Buffers disabled VGND -
30mV
V
Buffers enabled VGND +
100mV
High input voltage
Buffers disabled VAVDD +
30mV
Buffers enabled VAVDD -
100mV
DC Input Leakage Sleep mode Q1FA
AIN Dynamic Input Current Buffer disabled Q1.4 FA/V
Buffer enabled Q20 nA
REF Dynamic Input Current Buffer disabled Q2.1 FA/V
Buffer enabled Q30 nA
AIN Input Capacitance Buffer disabled 5 pF
REF Input Capacitance Buffer disabled 7.5 pF
AIN Voltage Range Unipolar 0 VREF V
Bipolar -VREF +VREF
Input Sampling Rate fSLINEF = 0 246 kHz
LINEF = 1 204.8
REF Voltage Range
Buffers disabled 0 VAVDD
V
Buffers enabled 0.1 VAVDD
- 0.1
REF Sampling Rate LINEF = 0 246 kHz
LINEF = 1 204.8
LOGIC INPUTS (SCLK, CLK, DIN, GPIO1–GPIO4)
Input Current Input leakage current Q1FA
Input Low Voltage VIL 0.3 x
VDVDD V
Input High Voltage VIH 0.7 x
VDVDD V
Input Hysteresis VHYS 200 mV
External Clock
60Hz line frequency 2.4576
MHz55Hz line frequency 2.25275
50Hz line frequency 2.048
LOGIC OUTPUTS (RDY/DOUT, GPIO1–GPIO4)
Output Low Level VOL IOL = 1mA; also tested for VDVDD = 3.6V 0.4 V
Output High Level VOH IOH = 1mA; also tested for VDVDD = 3.6V 0.9 x
VDVDD V
Leakage Current High-impedance state Q500 nA
Output Capacitance High-impedance state 9 pF
4 Maxim Integrated
18-Bit, Single-Channel, Ultra-Low-Power, Delta-
Sigma ADCs with Programmable Gain and GPIO
MAX11209/MAX11211
ELECTRICAL CHARACTERISTICS (continued)
(VAVDD = +3.6V, VDVDD = +1.7V, VREFP - VREFN = VAVDD; internal clock, single-cycle mode (SCYCLE = 1), TA = TMIN to TMAX,
unless otherwise noted. Typical values are at TA = +25NC under normal conditions, unless otherwise noted.)
Note 2: These specifications are not fully tested and are guaranteed by design and/or characterization.
Note 3: VAINP = VAINN.
Note 4: ppmFSR is parts per million of full scale.
Note 5: Positive full-scale error includes zero-scale errors (unipolar offset error or bipolar zero error) and applies to both unipolar
and bipolar input ranges.
Note 6: For data rates (1, 2.5, 5, 10, 15)sps and (0.83, 2.08, 4.17, 8.33, 12.5)sps.
Note 7: Normal-mode rejection of power line frequencies of 60Hz/50Hz apply only for single-cycle data rates at 15sps/10sps and
lower or continuous data rate of 60sps/50sps.
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
POWER REQUIREMENTS
Analog Supply VAVDD 2.7 3.6 V
Digital Supply VDVDD 1.7 3.6 V
Total Operating Current AVDD + DVDD Buffers disabled 235 300 FA
Buffers enabled 255
AVDD Sleep Current 0.15 2 FA
AVDD Operating Current Buffers disabled 185 235 FA
Buffers enabled 205
DVDD Sleep Current 0.25 2 FA
DVDD Operating Current 50 65 FA
SPI TIMING CHARACTERISTICS
SCLK Frequency fSCLK 5 MHz
SCLK Clock Period tCP 200 ns
SCLK Pulse-Width High tCH 80 ns
SCLK Pulse-Width Low tCL 60% duty cycle at 5MHz 80 ns
CS Low to 1st SCLK Rise Setup tCSS0 40 ns
CS High to 17th SCLK Setup tCSS1 40 ns
CS High After 16th SCLK
Falling Edge Hold tCSH1 3 ns
CS Pulse-Width High tCSW 40 ns
DIN to SCLK Setup tDS 40 ns
DIN Hold After SCLK tDH 0 ns
RDY/DOUT Transition Valid After
SCLK Fall tDOT Output transition time, data changes on
falling edge of SCLK 40 ns
RDY/DOUT Remains Valid After
SCLK Fall tDOH Output hold time allows for negative edge
data read 3 ns
RDY/DOUT Valid Before SCLK Rise tDOL tDOL = tCL - tDOT 40 ns
CS Rise to RDY/DOUT Disable tDOD CLOAD = 20pF 25 ns
CS Fall to RDY/DOUT Valid tDOE
Default value of RDY is 1 for minimum
specification; maximum specification for
valid 0 on RDY/DOUT
0 40 ns
DATA Fetch tDF
Maximum time after RDY asserts to read
DATA register; tCNV is the time for one
conversion
0tCNV -
60 x tCP
5Maxim Integrated
18-Bit, Single-Channel, Ultra-Low-Power, Delta-
Sigma ADCs with Programmable Gain and GPIO
MAX11209/MAX11211
Typical Operating Characteristics
(VAVDD = 3.6V, VDVDD = 1.8V, VREFP - VREFN = 2.5V; internal clock; TA = TMIN to TMAX, unless otherwise noted. Typical values are
at TA = +25NC.)
DIGITAL SLEEP CURRENT
vs. DVDD VOLTAGE
MAX11209/11 toc09
DVDD VOLTAGE (V)
CURRENT (µA)
3.53.33.12.92.72.52.32.11.9
0.5
1.0
1.5
2.0
2.5
3.0
0
1.7
TA = +85°C
TA = +25°C
TA = -45°C
DIGITAL ACTIVE CURRENT
vs. DVDD VOLTAGE
MAX11209/11 toc08
DVDD VOLTAGE (V)
CURRENT (µA)
3.43.22.8 3.02.0 2.2 2.4 2.61.8
50
60
70
80
90
100
110
120
130
40
1.6 3.6
LINEF = 0, LINEF = 1
TA = -45°C, +25°C, +85°C
LINEF = 0
LINEF = 1
TA = +85°C
TA = -45°C
SLEEP CURRENT vs. TEMPERATURE
MAX11209/11 toc07
TEMPERATURE (°C)
CURRENT (µA)
75553515-5-25
0.2
0.4
0.6
0.8
1.0
0
-45 95
TOTAL
DVDD
AVDD
ACTIVE SUPPLY CURRENT
vs. TEMPERATURE (LINEF = 1)
MAX11209/11 toc06
TEMPERATURE (°C)
CURRENT (µA)
75553515-5-25
50
100
150
200
250
300
0
-45 95
VDVDD = 1.8V
VAVDD = 3.0V
TOTAL
ACTIVE SUPPLY CURRENT
vs. TEMPERATURE (LINEF = 0)
MAX11209/11 toc05
TEMPERATURE (°C)
CURRENT (µA)
75553515-5-25
50
100
150
200
250
300
0
-45 95
VDVDD = 1.8V
VAVDD = 3.0V
TOTAL
ANALOG SLEEP CURRENT
vs. AVDD VOLTAGE
MAX11209/11 toc04
AVDD VOLTAGE (V)
CURRENT (µA)
3.4 3.53.33.23.13.02.92.8
0.2
0.4
0.6
0.8
1.0
0
2.7 3.6
TA = -45°C, +25°C, +85°C
TA = +85°C
TA = -45°C
ANALOG ACTIVE CURRENT vs. AVDD VOLTAGE
(SIGNAL AND REFERENCE BUFFERS ENABLED)
MAX11209/11 toc03
AVDD VOLTAGE (V)
CURRENT (µA)
3.453.303.153.002.85
180
200
220
240
260
280
160
2.70 3.60
TA = +85°C
TA = +25°C
TA = -45°C
ANALOG ACTIVE CURRENT vs. AVDD VOLTAGE
(SIGNAL OR REFERENCE BUFFERS ENABLED)
MAX11209/11 toc02
AVDD VOLTAGE (V)
CURRENT (µA)
3.453.303.153.002.85
140
160
180
200
220
240
260
120
2.70 3.60
SIGNAL BUFFERS
TA = +85°C
TA = +25°C
TA = -45°C
ANALOG ACTIVE CURRENT vs. AVDD VOLTAGE
(NO BUFFERS ENABLED)
MAX11209/11 toc01
AVDD VOLTAGE (V)
CURRENT (µA)
3.453.303.153.002.85
140
160
180
200
220
240
260
120
2.70 3.60
LINEF = 0, LINEF = 1
LINEF = 1
TA = +85°C
TA = +25°C
TA = -45°C
6 Maxim Integrated
18-Bit, Single-Channel, Ultra-Low-Power, Delta-
Sigma ADCs with Programmable Gain and GPIO
MAX11209/MAX11211
Typical Operating Characteristics (continued)
(VAVDD = 3.6V, VDVDD = 1.8V, VREFP - VREFN = 2.5V; internal clock; TA = TMIN to TMAX, unless otherwise noted. Typical values are
at TA = +25NC.)
CMRR vs. FREQUENCY
MAX11209/11 toc16
FREQUENCY (Hz)
CMRR (dB)
10,000100010010
-120
-100
-80
-60
-40
-20
0
-140
1 100,000
10sps
120sps
PSRR vs. FREQUENCY
(DATA RATE 10sps)
MAX11209/11 toc15
FREQUENCY (Hz)
PSRR (dB)
10,000100010010
-120
-100
-80
-60
-40
-20
0
-140
1 100,000
DVDD
AVDD
PSRR vs. FREQUENCY
(DATA RATE 120sps)
MAX11209/11 toc14
FREQUENCY (Hz)
PSRR (dB)
10,000100010010
-120
-100
-80
-60
-40
-20
0
-140
1 100,000
DVDD
AVDD
TUE vs. INPUT VOLTAGE
MAX11209/11 toc13
INPUT VOLTAGE (V)
INL (ppmFSR)
2.01.50.5 1.0-1.5 -1.0 -0.5 0-2.0
-8
-6
-4
-2
0
2
4
6
8
10
-10
-2.5 2.5
TA = +85°C
TA = -45°C
TA = +25°C
VIN(CM) = 1.8V
INTEGRAL NONLINEARITY
vs. INPUT VOLTAGE
MAX11209/11 toc12
INPUT VOLTAGE (V)
INL (ppmFSR)
2.01.50.5 1.0-1.5 -1.0 -0.5 0-2.0
-8
-6
-4
-2
0
2
4
6
8
10
-10
-2.5 2.5
TA = +85°C TA = -45°C
TA = +25°C
VIN(CM) = 1.8V
INTERNAL OSCILLATOR FREQUENCY
vs. AVDD VOLTAGE
MAX11209/11 toc11
AVDD VOLTAGE (V)
FREQUENCY (MHz)
3.453.15 3.303.002.85
1.7
1.6
1.8
1.9
2.0
2.1
2.2
2.3
2.4
2.5
2.6
2.7
2.8
2.9
3.0
1.5
2.70 3.60
LINEF = 1
LINEF = 0
INTERNAL OSCILLATOR FREQUENCY
vs. TEMPERATURE
MAX11209/11 toc10
TEMPERATURE (°C)
FREQUENCY (MHz)
755515 35-5-25
1.7
1.6
1.8
1.9
2.0
2.1
2.2
2.3
2.4
2.5
2.6
2.7
2.8
2.9
3.0
1.5
-45 95
VAVDD = 3.0V
LINEF = 1
LINEF = 0
7Maxim Integrated
18-Bit, Single-Channel, Ultra-Low-Power, Delta-
Sigma ADCs with Programmable Gain and GPIO
MAX11209/MAX11211
Functional Diagram
TIMING CLOCK GENERATOR
DIGITAL LOGIC
AND SERIAL-
INTERFACE
CONTROLLER
3RD-ORDER
DELTA-SIGMA
MODULATOR
SCLK
DIN
CLK
GPIO
CS
RDY/DOUT
GPIO1
GPIO2
GPIO3
GPIO4
AVDD
REFP
REFN
AINP
AINN
DVDD
GND
*PROGRAMMABLE GAIN ONLY AVAILABLE ON THE MAX11209.
DIGITAL FILTER
(SINC4)
PROGRAMMABLE
GAIN*
1–128
MAX11209*
MAX11211
8 Maxim Integrated
18-Bit, Single-Channel, Ultra-Low-Power, Delta-
Sigma ADCs with Programmable Gain and GPIO
MAX11209/MAX11211
Pin Description
Pin Configuration
16
15
14
13
12
11
10
9
1
2
3
4
5
6
7
8
GPIO1 GPIO4
CLK
SCLK
RDY/DOUT
DIN
CS
DVDD
AVDD
TOP VIEW
QSOP
GPIO2
GPIO3
REFN
GND
REFP
AINN
AINP
+
MAX11209
MAX11211
PIN NAME FUNCTION
1 GPIO1 General-Purpose I/O 1. Register controllable using SPI.
2 GPIO2 General-Purpose I/O 2. Register controllable using SPI.
3 GPIO3 General-Purpose I/O 3. Register controllable using SPI.
4 GND Ground. Ground reference for analog and digital circuitry.
5 REFP Differential Reference Positive Input. REFP must be more positive than REFN. Connect REFP to a voltage
between AVDD and GND.
6 REFN Differential Reference Negative Input. REFN must be more negative than REFP. Connect REFN to a volt-
age between AVDD and GND.
7 AINN Negative Fully Differential Analog Input
8 AINP Positive Fully Differential Analog Input
9 AVDD Analog Supply Voltage. Connect a supply voltage between +2.7V and +3.6V with respect to GND.
10 DVDD Digital Supply Voltage. Connect a digital supply voltage between +1.7V and +3.6V with respect to GND.
11 CS Active-Low, Chip-Select Logic Input
12 DIN
Serial-Data Input. Data present at DIN is shifted to the device’s internal registers at the rising edge of the
serial clock at SCLK, when the device is accessed for an internal register write or for a command opera-
tion.
13 RDY/DOUT
Data Ready Output/Serial-Data Output. This output serves a dual function. In addition to the serial-data
output function, the RDY/DOUT also indicates that the data is ready when the RDY is logic-low. RDY/
DOUT changes on the falling edge of SCLK.
14 SCLK Serial-Clock Input. Apply an external serial clock to SCLK.
15 CLK
External Clock Signal Input. When external clock mode is selected (EXTCLK = 1), provide a 2.4576MHz
or 2.048MHz clock signal at CLK. Other frequencies can be used, but the data rate and digital filter
notch frequencies scale accordingly.
16 GPIO4 General-Purpose I/O 4. Register controllable using SPI.
9Maxim Integrated
18-Bit, Single-Channel, Ultra-Low-Power, Delta-
Sigma ADCs with Programmable Gain and GPIO
MAX11209/MAX11211
Detailed Description
The MAX11209/MAX11211 are ultra-low-power (< 300FA
active), high-resolution, low-speed, serial-output ADCs.
These ADCs provide the highest resolution per unit power
in the industry, and are optimized for applications that
require very high dynamic range with low power such
as sensors on a 4mA to 20mA industrial control loop.
Optional input buffers provide isolation of the signal inputs
from the switched capacitor sampling network, allow-
ing the devices to be used with very high impedance
sources without compromising available dynamic range.
The devices provide a high-accuracy internal oscillator,
which requires no external components. When used with
the specified data rates, the internal digital filter provides
more than 144dB rejection of 50Hz or 60Hz line noise. The
devices are highly configurable using the SPI interface
and include four GPIOs for external mux control.
Analog Inputs
The devices accept two analog inputs (AINP, AINN) in
buffered or unbuffered mode. The input buffer isolates
the inputs from the capacitive load presented by the
modulator, allowing for high source-impedance analog
transducers. The value of the SIGBUF bit in the CTRL1
register determines whether the input buffer is enabled
or disabled. See Table 12.
Input Voltage Range
The modulator input range is programmable for bipolar
(-VREF to +VREF) or unipolar (0 to VREF) ranges. The
U/B bit in the CTRL1 register configures the MAX11209/
MAX11211 for unipolar or bipolar transfer functions. See
Table 12.
System Clock
The devices incorporate a highly stable internal oscillator
that provides the system clock. The system clock runs
the internal state machine and is trimmed to 2.4576MHz
or 2.048MHz. The internal oscillator clock is divided
down to run the digital and analog timing. The LINEF bit
in the CTRL1 register determines the internal oscillator
frequency. See Tables 10 and 12. Set LINEF = 0 to select
the 2.4576MHz oscillator and LINEF = 1 to select the
Table 1. Continuous Conversion with SCYCLE Bit = 0
Table 2. Single-Cycle Conversion with SCYCLE Bit = 1
*LINEF = 0 sets the clock frequency to 2.4576MHz and the input sampling frequency to 245.76kHz. LINEF bit = 1 sets the clock
frequency to 2.048MHz and the input sampling frequency to 204.8kHz.
*LINEF = 0 sets the clock frequency to 2.4576MHz and the input sampling frequency to 245.76kHz. LINEF bit = 1 sets the clock
frequency to 2.048MHz and the input sampling frequency to 204.8kHz.
RATE[2:0] DATA RATE* (sps) BIPOLAR NFR
(BITS)
BIPOLAR
ENOB
(BITS)
UNIPOLAR
NFR (BITS)
UNIPOLAR
ENOB
(BITS)
OUTPUT
NOISE
(µVRMS)
LINEF = 0 LINEF = 1
100 60 50 18.0 18.0 18.0 18.0 0.74
101 120 100 18.0 18.0 18.0 18.0 1.03
110 240 200 18.0 18.0 18.0 18.0 1.45
111 480 400 18.0 18.0 18.0 18.0 2.21
RATE[2:0]
SINGLE-CYCLE DATA RATE*
(sps) BIPOLAR
NFR (BITS)
BIPOLAR
ENOB
(BITS)
UNIPOLAR
NFR (BITS)
UNIPOLAR
ENOB (BITS)
OUTPUT
NOISE
(µVRMS)
LINEF = 0 LINEF = 1
000 1 0.833 18.0 18.0 18.0 18.0 0.21
001 2.5 2.08 18.0 18.0 18.0 18.0 0.27
010 5 4.17 18.0 18.0 18.0 18.0 0.39
011 10 8.33 18.0 18.0 18.0 18.0 0.55
100 15 12.5 18.0 18.0 18.0 18.0 0.74
101 30 25 18.0 18.0 18.0 18.0 1.03
110 60 50 18.0 18.0 18.0 18.0 1.45
111 120 100 18.0 18.0 18.0 18.0 2.21
10 Maxim Integrated
18-Bit, Single-Channel, Ultra-Low-Power, Delta-
Sigma ADCs with Programmable Gain and GPIO
MAX11209/MAX11211
2.048MHz oscillator. The 2.4576MHz oscillator provides
maximum 60Hz rejection, and the 2.048MHz oscillator
provides maximum 50Hz rejection. See Figures 1 and
2. For optimal simultaneous 50Hz and 60Hz rejection,
apply a 2.25275MHz external clock at CLK.
Reference
The devices provide differential inputs REFP and REFN
for an external reference voltage. Connect the external
reference directly across the REFP and REFN to obtain
the differential reference voltage. The common-mode
voltage range for VREFP and VREFN is between 0 and
VAVDD.
The devices accept reference inputs in buffered or
unbuffered mode. The value of the REFBUF bit in the
CTRL1 register determines whether the reference buffer
is enabled or disabled. See Table 12.
Buffers
The devices include reference and signal input buffers
capable of reducing the average input current from
2.1FA/V on the reference inputs and from 1.4FA/V on
the analog inputs to a constant 30nA current on the
reference inputs and 20nA current on the analog inputs.
The reference and signal input buffers can be selected
individually by programming the CTRL1 register bits
REFBUF and SIGBUF. When enabled, the reference and
input signal buffers require an additional 20FA from the
AVDD supply pin.
Power-On Reset (POR)
The devices utilize power-on reset (POR) supply-mon-
itoring circuitry on both the digital supply (DVDD) and
the analog supply (AVDD). The POR circuitry ensures
proper device default conditions after either a digital or
analog power sequencing event. The digital POR trig-
ger threshold is approximately 1.2V and has 100mV of
hysteresis. The analog POR trigger threshold is approxi-
mately 1.25V and has 100mV of hysteresis. Both POR
circuits have lowpass filters that prevent high-frequency
supply glitches from triggering the POR.
Calibration
The devices provide two sets of calibration registers
which offer the user several options for calibrating
their system. The calibration register value defaults
are all zero, which require a user to either perform
a calibration or program the register through the SPI
interface to use them. The on-chip calibration reg-
isters are enabled or disabled by programming the
NOSYSG, NOSYSO, NOSCG, and NOSCO bits in the
CTRL3 register. The default values for these calibra-
tion control bits are 1, which disables the use of the
internal calibration registers.
The devices power up with the internal calibration regis-
ters disabled, and therefore a full-scale input produces
a result of 60% of the full-scale digital range. To use the
full-scale digital range a calibration must be performed.
The first level of calibration is the self-calibration where
the part performs the required connections to zero and
full-scale internally. This level of calibration is typically
sufficient for 1FV of offset accuracy and 2ppm of full-
scale accuracy. The self-calibration routine does not
include the source resistance effects from the signal
source driving the input pins, which can change the off-
set and gain of the system.
A second level of calibration is available where the user
can calibrate a system zero scale and system full scale
by presenting a zero-scale signal or a full-scale signal
to the input pins and initiating a system zero scale or
system gain calibration command.
A third level of calibration allows for the user to write to
the internal calibration registers through the SPI interface
to achieve any digital offset or scaling the user requires
with the following restrictions. The range of digital offset
correction is QVREF/4. The range of digital gain correc-
tion is from 0.5 to 1.5. The resolution of offset correction
is 0.5 LSB.
The calibration operations are controlled with the CAL1
and CAL0 bits in the command byte. The user requests
a self-calibration by setting the CAL1 bit to 0 and CAL0
bit to 1. A self-calibration requires 200ms to complete,
and both the SCOC and SCGC registers contain the
values that correct the chip output for zero scale and full
scale. The user requests a system zero-scale calibration
by setting the CAL1 bit to 1 and the CAL0 bit to 0 and
presents a system zero-level signal to the input pins. The
SOC register contains the values that correct the chip
zero scale. The system zero calibration requires 100ms
to complete, and the SOC register contains values that
correct the chip zero scale. The user requests a system
full-scale calibration by setting the CAL1 bit to 1 and the
CAL0 bit to 1 and presents a system full-scale signal
level to the input pins. The system full-scale calibration
requires 100ms to complete, and the SGC register con-
tains values that correct for the chip full-scale value. See
Tables 3a and 3b for an example of a self-calibration
sequence and a system calibration sequence.
11Maxim Integrated
18-Bit, Single-Channel, Ultra-Low-Power, Delta-
Sigma ADCs with Programmable Gain and GPIO
MAX11209/MAX11211
Noise vs. Data Rate
The devices offer software-selectable internal oscillator
frequencies as well as software-selectable output data
rates. The LINEF bit in the CTRL1 register (Table 12)
determines the internal oscillator frequency. The RATE
bits in the command byte (Table 8) determine the ADC’s
output data rate. The devices also offer the option of
running in zero latency single-cycle conversion mode
(Table 2) or continuous conversion mode (Table 1). Set
SCYCLE = 0 in the CTRL1 register (Table 12) to run in
continuous conversion mode and SCYCLE = 1 for single-
cycle conversion mode.
Single-cycle conversion mode gives an output result with
no data latency. The devices output data up to 100sps
(2.048MHz internal oscillator) or 120sps (2.4576MHz
internal oscillator) with no data latency. In continuous
conversion mode, the output data rate is four times the
single-cycle conversion mode, for sample rates up to
400sps or 480sps. In continuous conversion mode, the
output data requires three additional 24-bit cycles to
settle from an input step.
Digital Filter
The devices include a SINC4 digital filter that produces
spectral nulls at the multiples of the data rate. For all
data rates less than 30sps, a spectral null occurs at the
line frequency of 60Hz and is guaranteed to attenuate
60Hz normal-mode components by more than 100dB.
Simultaneous 50Hz and 60Hz attenuation can be accom-
plished by using an external clock with a frequency of
2.25275MHz. This guarantees a minimum of 80dB rejec-
tion at 50Hz and 85dB rejection at 60Hz. The SINC4 filter
has a -3dB frequency equal to 24% of the data rate. See
Figures 1 and 2.
GPIOs
The devices provide four GPIO ports. When set as out-
puts, these digital I/Os can be used to drive the digital
inputs to a multiplexer or multichannel switch. Figure 3
details an example where four single-ended signals are
multiplexed in a break-before-make switching sequence,
using the MAX313, a quad SPST analog switch.
The devices’ GPIO ports are configurable through the
CTRL2 register. See Table 13. To select AIN1, write the
command to CTRL2 according to Table 4a. This selects
all GPIOs as outputs, as well as setting all logic signals
to 0 except the selected channel AIN1.
To select channel AIN3 next, it is a good idea to set all
switches to a high-impedance state first (see Table 4b).
Then select channel AIN3 by driving IN3 high (see
Table 4c).
Table 3a. Example of Self-Calibration
Table 3b. Example of System Calibration
STEP DESCRIPTION
REGISTER BIT
SCOC SCGC SOC SGC
NOSYSG
NOSYSO
NOSCG
NOSCO
1Initial power-up 0x000000 0x000000 0x000000 0x000000 1 1 1 1
2Enable self-calibration registers 0x000000 0x000000 0x000000 0x000000 1 1 0 0
3Self-calibration, DIN = 10010000 0x00007E 0xBFD345 0x000000 0x000000 1 1 0 0
STEP DESCRIPTION
REGISTER BIT
SCOC SCGC SOC SGC
NOSYSG
NOSYSO
NOSCG
NOSCO
1Initial power-up 0x000000 0x000000 0x000000 0x000000 1 1 1 1
2Enable self-calibration registers 0x000000 0x000000 0x000000 0x000000 1 1 0 0
3Self-calibration, DIN = 10010000 0x00007E 0xBFD345 0x000000 0x000000 1 1 0 0
4Enable system offset register 0x00007E 0xBFD345 0x000000 0x000000 1 0 0 0
5System-calibration offset, DIN = 1010000 0x00007E 0xBFD345 0xFFEE1D 0x000000 1 0 0 0
6Enable system gain register 0x00007E 0xBFD345 0xFFEE1D 0x000000 0 0 0 0
7System-calibration gain, DIN = 1011000 0x00007E 0xBFD345 0xFFEE1D 0x81CB5B 0 0 0 0
12 Maxim Integrated
18-Bit, Single-Channel, Ultra-Low-Power, Delta-
Sigma ADCs with Programmable Gain and GPIO
MAX11209/MAX11211
Figure 1. Normal-Mode Frequency Response (2.4576MHz Oscillator, LINEF = 0)
Figure 2. Normal-Mode Frequency Response (2.048MHz Oscillator, LINEF = 1)
Table 4a. Data Command to Select Channel AIN1 in Figure 3
Table 4b. Set All Channels High Impedance in Figure 3
NORMAL MODE REJECTION
DATA RATE 10.0sps
FREQUENCY (Hz)
GAIN (dB)
90806040 7030 502010
-130
-140
-120
-110
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
-150
0 100
NORMAL MODE REJECTION
DATA RATE 120.0sps
FREQUENCY (Hz)
GAIN (dB)
180016001200800 1400600 1000400200
-130
-140
-120
-110
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
-150
0 2000
NORMAL MODE REJECTION
DATA RATE 8.333sps
FREQUENCY (Hz)
GAIN (dB)
90806040 7030 502010
-130
-140
-120
-110
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
-150
0 100
NORMAL MODE REJECTION
DATA RATE 100.000sps
FREQUENCY (Hz)
GAIN (dB)
180016001200800 1400600 1000400200
-130
-140
-120
-110
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
-150
0 2000
BIT B7 B6 B5 B4 B3 B2 B1 B0
BIT NAME DIR4 DIR3 DIR2 DIR1 DIO4 DIO3 DIO2 DIO1
VALUE 11110001
BIT B7 B6 B5 B4 B3 B2 B1 B0
BIT NAME DIR4 DIR3 DIR2 DIR1 DIO4 DIO3 DIO2 DIO1
VALUE 11110000
13Maxim Integrated
18-Bit, Single-Channel, Ultra-Low-Power, Delta-
Sigma ADCs with Programmable Gain and GPIO
MAX11209/MAX11211
It is not always necessary to transition to a high-imped-
ance state between channel selections, but depends on
the source analog signals as well as the control structure
of the multiplexed switches.
Digital Programmable Gain (MAX11209)
The MAX11209 offers programmable gain settings that
can be digitally set to 1, 2, 4, 8, 16, 32, 64, or 128. The
DGAIN_ bits in the CTRL3 register (see Table 14) config-
ure the digital gain setting and control the input referred
gain. The MAX11209’s input range is 0V to VREF/
gain (unipolar) or ±VREF/gain (bipolar). The MAX11209
always outputs 18 bits of data. But as this is a digital
programmable gain, the noise floor remains constant,
depending on the output rate setting. At an output rate of
10sps, as shown in Figure 4, the noise floor is such that
all gain settings from 1 to 32 provide 18 bits of noise-free
resolution. A gain setting of 128 at 10sps means the LSB
is below the noise floor. The MAX11209 digital gain is
beneficial for low-voltage applications that only require a
small portion of the 0V to VREF or ±VREF ranges.
Table 4c. Data Command to Select Channel AIN3 in Figure 3
Figure 4. MAX11209 Digital Programmable Gain Example (10sps Output Rate)
Figure 3. MAX11209 GPIOs Drive an External 4-Channel
Switch (MAX313)
AIN1
AIN2
AIN3
AIN4
IN1
IN2
IN3
IN4
COM1
COM2
COM3
COM4
GPIO1
GPIO2
GPIO3
GPIO4
AINP
AINN
MAX313
LOGIC SWITCH
0 OFF
1ON
MAX11209MAX313
MSB
LSB
NOISE FLOOR
REMAINS CONSTANT
AT 0.55µVRMS
BITS USED FOR GAIN = 16
BITS USED FOR GAIN = 2
BITS USED FOR GAIN = 1
SUB-LSBs
18-BIT OUTPUT DATA CYCLE
VREF = 3V
BITS USED FOR GAIN = 128
BIT B7 B6 B5 B4 B3 B2 B1 B0
BIT NAME DIR4 DIR3 DIR2 DIR1 DIO4 DIO3 DIO2 DIO1
VALUE 11110100
14 Maxim Integrated
18-Bit, Single-Channel, Ultra-Low-Power, Delta-
Sigma ADCs with Programmable Gain and GPIO
MAX11209/MAX11211
Figure 5. SPI Command Byte
Figure 6. SPI Register Access Write
Serial-Digital Interface
The MAX11209/MAX11211 interface is fully compatible
with SPI-, QSPI-, and MICROWIRE-standard serial inter-
faces. The SPI interface provides access to nine on-chip
registers that are 8 or 24 bits wide.
Drive CS low to transfer data in and out of the devices.
Clock in data at DIN on the rising edge of SCLK. The
RDY/DOUT output serves two functions: conversion sta-
tus and data read. To find the conversion status, assert
CS low and read the RDY/DOUT output; the conversion
is in progress if the RDY/DOUT output reads logic-high
and the conversion is complete if the RDY/DOUT output
reads logic-low. Data at RDY/DOUT changes on the
falling edge of SCLK and is valid on the rising edge of
SCLK. DIN and DOUT are transferred MSB first. Drive
CS high to force DOUT high impedance and cause
the devices to ignore any signals on SCLK and DIN.
Connect CS low for 3-wire operation. Figures 5, 6, and 7
show the SPI timing diagrams.
tCSH0
tDOE
HIGH-Z
tDOD
HIGH-Z
tCSS0
SCLK 0
X
1
10CAL1 CAL0 IMPD RATE2 RATE1 RATE0
8
DIN
tDH
tCP tCSH1
tCSS1
tCSW
tCL tCH
tDS
CS
RDY/DOUT
tCSH0
tDOE
HIGH-Z tDOD
HIGH-Z
tCSS0
SCLK 0
X
1
11X RS3 RS2 RS1 RS0 W/R D7 D6 D5 D4 D3 D2 D1 D0
1689
DIN
tDH
tCP
tCSH1
tCSS1
tCSW
tCL tCH
tDS
CS
RDY/DOUT
SPI REGISTER ACCESS WRITE
15Maxim Integrated
18-Bit, Single-Channel, Ultra-Low-Power, Delta-
Sigma ADCs with Programmable Gain and GPIO
MAX11209/MAX11211
Figure 7. SPI Register Access Read
Table 5. Command Byte (MODE = 0)
Table 6. Command Byte (MODE = 1)
Note: The START bit is used to synchronize the data from the host device. The START bit is always 1.
Command Byte
Communication between the user and the device is con-
ducted through SPI using a command byte. The com-
mand byte consists of two modes differentiated as com-
mand modes and data modes. Command modes and
data modes are further differentiated by decoding the
remaining bits in the command byte. The mode selected
is determined by the MODE bit. If the MODE bit is 0, then
the user is requesting either a conversion, calibration, or
power-down; see Table 5. If the MODE bit is 1, then the
user is selecting a data command and can either read
from or write to a register; see Table 6.
The Status register (STAT1) is a read-only register and
provides general chip operational status to the user. If
the user attempts to calibrate the system and overranges
the internal signal scaling, then a gain overrange condi-
tion is flagged with the SYSOR bit. The last data rate
programmed for the ADC is available in the RATE bits.
If the input signal has exceeded positive or negative full
scale, this condition is flagged with the OR and UR bits.
If the modulator is busy converting, then the MSTAT bit
is set. If a conversion result is ready for readout, the RDY
bit is set; see Table 11.
The Control 1 register (CTRL1) is a read/write register,
and the bits determine the internal oscillator frequency,
unipolar or bipolar input range, selection of an internal or
external clock, enabling or disabling the reference and
input signal buffers, the output data format (offset binary
or two’s complement), and single-cycle or continuous
conversion mode. See Table 12.
The Control 2 register (CTRL2) is a read/write register,
and the bits configure the GPIOs as inputs or outputs
and their values. See Table 13.
The Control 3 register (CTRL3) is a read/write register,
and the bits determine the MAX11209 programmable
gain setting and the calibration register settings for both
the MAX11209 and MAX11211. See Table 14.
The Data register (DATA) is a read-only register. Data is
output from RDY/DOUT on the next 24 SCLK cycles once
CS is forced low. The data bits transition on the falling
edge of SCLK. Data is output MSB first, and is offset
binary or two’s complement, depending on the setting
of the FORMAT bit in the CTRL1 register. See Table 15.
The System Offset Calibration register (SOC) is a read/
write register, and the bits contain the digital value that
corrects the data for system zero scale. See Table 17.
The System Gain Calibration register (SGC) is a read/
write register, and the bits contain the digital value that
corrects the data for system full scale. See Table 18.
The Self-Cal Offset Calibration register (SCOC) is a read/
write register, and the bits contain the value that corrects
the data for chip zero scale. See Table 19.
The Self-Cal Gain Calibration register (SCGC) is a read/
write register, and the bits contain the value that corrects
the data for chip full scale. See Table 20.
tDOE
HIGH-Z HIGH-Z
SCLK
X
1
11X RS3 RS2 RS1 RS0 W/R XX XXXXXX
D6D7 D5 D4 D3 D2 D1 D0
1689
DIN
tCP tDOD
tDOT
tDO1
tDOH
CS
RDY/DOUT
tCSS0
tDS
tCSS1
tCL tCH
tDH
BIT B7 B6 B5 B4 B3 B2 B1 B0
BIT NAME START = 1 MODE = 0 CAL1 CAL0 IMPD RATE2 RATE1 RATE0
BIT B7 B6 B5 B4 B3 B2 B1 B0
BIT NAME START = 1 MODE = 1 0 RS3 RS2 RS1 RS0 W/R
16 Maxim Integrated
18-Bit, Single-Channel, Ultra-Low-Power, Delta-
Sigma ADCs with Programmable Gain and GPIO
MAX11209/MAX11211
Table 7. Operating Mode (MODE Bit)
Table 8. Command Byte (MODE = 0, LINEF = 0)
Table 9. Register Selection (MODE = 1)
COMMAND START MODE CAL1 CAL0 IMPD RATE2 RATE1 RATE0
Self-calibration cycle 1 0 0 1 0 0 0 0
System offset calibration cycle 1 0 1 0 0 0 0 0
System gain calibration 1 0 1 1 0 0 0 0
Immediate power-down 1 0 0 0 1 0 0 0
Convert 1sps 1 0 0 0 0 0 0 0
Convert 2.5sps 1 0 0 0 0 0 0 1
Convert 5sps 1 0 0 0 0 0 1 0
Convert 10sps 1 0 0 0 0 0 1 1
Convert 15sps 1 0 0 0 0 1 0 0
Convert 30sps 1 0 0 0 0 1 0 1
Convert 60sps 1 0 0 0 0 1 1 0
Convert 120sps 1 0 0 0 0 1 1 1
RS3 RS2 RS1 RS0 REGISTER ACCESS POWER-ON RESET STATUS REGISTER SIZE (BITS)
0 0 0 0 STAT1 0x00 8
0 0 0 1 CTRL1 0x02 8
0 0 1 0 CTRL2 0x0F 8
0 0 1 1 CTRL3 0x1E 8
0 1 0 0 DATA 0x000000 24
0 1 0 1 SOC 0x000000 24
0 1 1 0 SGC 0x000000 24
0 1 1 1 SCOC 0x000000 24
1 0 0 0 SCGC 0x000000 24
MODE BIT SETTING OPERATING MODE
0The command byte initiates a conversion or an immediate power-down. See Tables 5 and 8.
1The device interprets the command byte as a register access byte, which is decoded as per
Tables 6 and 9.
17Maxim Integrated
18-Bit, Single-Channel, Ultra-Low-Power, Delta-
Sigma ADCs with Programmable Gain and GPIO
MAX11209/MAX11211
Table 10. Register Address Map
*These DGAIN_ bits set the digital gain for the MAX11209 These bits are don’t-care bits for the MAX11211.
REGISTER
NAME R/WADDRESS
SEL (RS[3:0]) B7 B6 B5 B4 B3 B2 B1 B0
STAT1 R 0x0 SYSOR RATE2 RATE1 RATE0 OR UR MSTAT RDY
CTRL1 R/W0x1 LINEF U/BEXTCLK REFBUF SIGBUF FORMAT SCYCLE RESERVED
CTRL2 R/W0x2 DIR4 DIR3 DIR2 DIR1 DIO4 DIO3 DIO2 DIO1
CTRL3 R/W0x3 DGAIN2* DGAIN1* DGAIN0* NOSYSG NOSYSO NOSCG NOSCO RESERVED
DATA R 0x4
D[17:16]
D[15:8]
D[7:0]
SOC R/W0x5
B[23:16]
B[15:8]
B[7:0]
SGC R/W0x6
B[23:16]
B[15:8]
B[7:0]
SCOC R/W0x7
B[23:16]
B[15:8]
B[7:0]
SCGC R/W0x8
B[23:16]
B[15:8]
B[7:0]
18 Maxim Integrated
18-Bit, Single-Channel, Ultra-Low-Power, Delta-
Sigma ADCs with Programmable Gain and GPIO
MAX11209/MAX11211
STAT1: Status Register
SYSOR: The system gain overrange bit, when set to 1, indicates that a system gain calibration was over range. The
SCGC calibration coefficient is maximum value of 1.9999999. This bit, when set to 1, indicates that the full-scale value
out of the converter is likely not available.
RATE[2:0]: The data rate bits indicate the conversion rate that corresponds to the result in the DATA register or the
rate that was used for calibration coefficient calculation. If the previous conversions were done at a different rate, the
RATE[2:0] bits indicate a rate different than the rate of the conversion in progress.
OR: The overrange bit, OR, is set to 1 to indicate the conversion result has exceeded the maximum value of the
converter and that the result has been clipped or limited to the maximum value. The OR bit is set to 0 to indicate the
conversion result is within the full-scale range of the device.
UR: The underrange bit, UR, is set to 1 to indicate the conversion result has exceeded the minimum value of the
converter and that the result has been clipped or limited to the minimum value. The UR bit is set to 0 to indicate the
conversion result is within the full-scale range of the device.
MSTAT: The measurement status bit, MSTAT is set to 1 when a signal measurement is in progress. When MSTAT = 1,
a conversion, self-calibration, or system calibration is in progress and indicates that the modulator is busy. When the
modulator is not converting, the MSTAT bit is set to 0.
RDY: The RDY ready bit is set to 1 to indicate that a conversion result is available. Reading the DATA register resets the
RDY bit to 0 only after another conversion has been initiated. If the DATA has not been read before another conversion
is initiated, the RDY bit remains 1; if the DATA is read before another conversion is initiated, the RDY bit resets to 0. If
the DATA for the previous conversion is read during a following conversion, the RDY bit is reset immediately after the
DATA read operation has completed.
Table 11. STAT1 Register (Read Only)
BIT B7 B6 B5 B4 B3 B2 B1 B0
BIT NAME SYSOR RATE2 RATE1 RATE0 OR UR MSTAT RDY
DEFAULT 00000000
19Maxim Integrated
18-Bit, Single-Channel, Ultra-Low-Power, Delta-
Sigma ADCs with Programmable Gain and GPIO
MAX11209/MAX11211
CTRL1: Control 1 Register
The byte-wide CTRL1 register is a bidirectional read/write register. The byte written to the CTRL1 register indicates if
the part converts continuously or single cycle, if an external or internal clock is used, if the reference and signal buffers
are activated, the format of the data when in bipolar mode, and if the analog signal input range is unipolar or bipolar.
LINEF: Use the line frequency bit, LINEF, to select if the data rate is centered for 50Hz power mains or 60Hz power
mains. To select data rates for 50Hz power mains, write 1 to LINEF and to select data rates for 60Hz power mains,
write 0 to LINEF.
U/B: The unipolar/bipolar bit, U/B, selects if the input range is unipolar or bipolar. A 1 in this bit location selects a uni-
polar input range and a 0 selects a bipolar input range.
EXTCLK: The external clock bit, EXTCLK, controls the selection of the system clock. A 1 enables an external clock as
system clock, whereas as a 0 enables the internal clock.
REFBUF: The reference buffer bit, REFBUF, enables/disables the reference buffers. A 1 enables the reference buffers.
A 0 powers down the reference buffers and the reference inputs bypass the reference buffers when driving the ADC.
SIGBUF: The signal buffer, SIGBUF, enables/disables the signal buffers. A 1 enables the signal buffer. A 0 powers
down the signal buffers and the analog signal inputs bypass the signal buffers when driving the ADC.
FORMAT: The format bit, FORMAT, controls the digital format of the data. Unipolar data is always in offset binary for-
mat. The bipolar format is two’s complement if the FORMAT bit is set to 0 or offset binary if the FORMAT bit is set to 1.
SCYCLE: The single-cycle bit, SCYCLE, determines if the device runs in “no-latency” single-conversion mode
(SCYCLE = 1) or if the device runs in “latent” continuous-conversion mode (SCYCLE = 0). When in single-cycle conver-
sion mode, the device completes one no-latency conversion and then powers down into a leakage-only state. When
in continuous-conversion mode, the part is continuously converting and the first three data from the part are incorrect
due to the SINC4 filter latency.
Important Note: When operating in continuous-conversion mode (SCYCLE = 0), it is recommended to keep CS low to
properly detect the end of conversion. The end of conversion is signaled by RDY/DOUT changing from 0 to 1. The tran-
sition of RDY/DOUT from 0 to 1 must be used to synchronize the DATA register read back. If the RDY/DOUT output is
not used to synchronize the DATA read back, a timing hazard exists where the DATA register is updated internally after
a conversion has completed simultaneously with the DATA register being read out, causing an incorrect read of DATA.
Table 12. CTRL1 Register (Read/Write)
BIT B7 B6 B5 B4 B3 B2 B1 B0
BIT NAME LINEF U/BEXTCLK REFBUF SIGBUF FORMAT SCYCLE UNUSED
DEFAULT 00000010
20 Maxim Integrated
18-Bit, Single-Channel, Ultra-Low-Power, Delta-
Sigma ADCs with Programmable Gain and GPIO
MAX11209/MAX11211
CTRL2: Control 2 Register
The byte-wide CTRL2 register is a bidirectional read/write register. The byte written to the CTRL2 register controls the
direction and values of the digital I/O ports.
DIR[4:1]: The direction bits configure the direction of the DIO bit. When a DIR bit is set to 0, the associated DIO bit
is configured as an input and the value returned by a read of the DIO bit is the value being driven on the associated
GPIO. When a DIR bit is set to 1, the associated DIO bit is configured as an output and the GPIO port is driven to a
logic value of the associated DIO bit.
DIO[4:1]: The data input/output bits are bits associated with the GPIO ports. When a DIO is configured as an input,
the value read from the DIO bit is the logic value being driven at the GPIO port. When the direction is configured as an
output, the GPIO port is driven to a logic value associated with the DIO bit.
CTRL3: Control 3 Register
The byte-wide CTRL3 register is a bidirectional read/write register. The CTRL3 register controls the operation and
calibration of the device.
DGAIN[2:0] (MAX11209 only): The digital gain bits control the input referred gain. With a gain of 1, the input range is
0 to VREF (unipolar) or ±VREF (bipolar). As the gain in increased by 2x, the input range is reduced to 0 to VREF/gain
or ±VREF/gain. Digital gain is applied to the final offset and gain-calibrated digital data. The DGAIN[2:0] bits decode
to digital gains as follows:
000 = 1 100 = 16
001 = 2 101 = 32
010 = 4 110 = 64
011 = 8 111 = 128
NOSYSG: The no-system gain bit, NOSYSG, controls the system gain calibration coefficient. A 1 in this bit location disables
the use of the system gain value when computing the final offset and gain corrected data value. A 0 in this location enables
the use of the system gain value when computing the final offset and gain corrected data value.
NOSYSO: The no system offset bit, NOSYSO, controls the system offset calibration coefficient. A 1 in this location disables
the use of the system offset value when computing the final offset and gain corrected data value. A 0 in this location enables
the use of the system offset value when computing the final offset and gain corrected data value.
NOSCG: The no self-calibration gain bit, NOSCG, controls the self-calibration gain calibration coefficient. A 1 in this location
disables the use of the self-calibration gain value when computing the final offset and gain corrected data value. A 0 in this
location enables the use of the self-calibration gain value when computing the final offset and gain corrected data value.
NOSCO: The no self-calibration offset bit, NOSCO, controls the use of the self-calibration offset calibration coefficient. A 1 in
this location disables the use of the self-calibration offset value when computing the final offset and gain corrected data value.
A 0 in this location enables the use of the self-calibration offset value when computing the final offset and gain corrected data
value.
Table 13. CTRL2 Register (Read/Write)
Table 14. CTRL3 Register (Read/Write)
*These DGAIN_ bits are don’t-care bits for the MAX11209.
BIT B7 B6 B5 B4 B3 B2 B1 B0
BIT NAME DIR4 DIR3 DIR2 DIR1 DIO4 DIO3 DIO2 DIO1
DEFAULT 00001111
BIT B7 B6 B5 B4 B3 B2 B1 B0
BIT NAME DGAIN2* DGAIN1* DGAIN0* NOSYSG NOSYSO NOSCG NOSCO RESERVED
DEFAULT 0 0 0 1 1 1 1 0
21Maxim Integrated
18-Bit, Single-Channel, Ultra-Low-Power, Delta-
Sigma ADCs with Programmable Gain and GPIO
MAX11209/MAX11211
DATA: Data Register
The data register is a 24-bit read-only register. Any attempt to write data to the data register has no effect. The data
read from this register is clocked out MSB first. The data register holds the conversion result. D17 is the MSB, and D0
is the LSB. The result is stored in a format according to the FORMAT bit in the CTRL1 register.
The data format while in unipolar mode is always straight binary. In straight binary format, the most negative value is
0x00000 (VAINP - VAINN = 0V), the midscale value is 0x20000 (VAINP - VAINN = VREF/2), and the most positive value
is 0x3FFFF (VAINP - VAINN = VREF).
In bipolar mode, if the FORMAT bit = 1, then the data format is offset binary. If the FORMAT bit = 0, then the data
format is two’s complement. In two’s complement the negative full-scale value is 0x20000 (VAINP - VAINN = -VREF), the
midscale is 0x00000 (VAINP - VAINN = 0V), and the positive full scale is 0x1FFFF (VAINP - VAINN = VREF). Any input
exceeding the available input range is limited to the minimum or maximum data value.
Table 15. DATA Register (Read Only)
Table 16a. Output Data Format for the Unipolar Input Range
BIT D17 D16 D15 D14 D13 D12 D11 D10
DEFAULT 00000000
BIT D9 D8 D7 D6 D5 D4 D3 D2
DEFAULT 00000000
BIT D1 D0 000000
DEFAULT 00000000
INPUT VOLTAGE
VAINP - VAINN
DIGITAL OUTPUT CODE FOR UNIPOLAR RANGE
STRAIGHT BINARY FORMAT
≥ VREF 0x3FFFF
0x3FFFF
0x00001
0 0x00000
REF 18
1
V1
21
×−
−
REF
18
V
21−
22 Maxim Integrated
18-Bit, Single-Channel, Ultra-Low-Power, Delta-
Sigma ADCs with Programmable Gain and GPIO
MAX11209/MAX11211
Table 16b. Output Data Formats for the Bipolar Input Range
Table 17. SOC Register (Read/Write)
SOC: System Offset Calibration Register
The system offset calibration register is a 24-bit read/write register. The data written/read to/from this register is clocked
in/out MSB (most significant bit) first. This register holds the system offset calibration value. The format is always in
two’s complement binary format. A write to the system-calibration register is allowed. The value written remains valid
until it is either rewritten or until an on-demand system-calibration operation is performed, which overwrites the user-
supplied value.
The system offset calibration value is subtracted from each conversion result provided the NOSYSO bit in the CTRL3
register is set to 0. The system offset calibration value is subtracted from the conversion result after self-calibration
but before system gain correction. The system offset calibration value is also applied prior to the 1x or 2x scale factor
associated with bipolar and unipolar modes.
BIT B23 B22 B21 B20 B19 B18 B17 B16
DEFAULT 00000000
BIT B15 B14 B13 B12 B11 B10 B9 B8
DEFAULT 0 0 0 0 0 0 0 0
BIT B7 B6 B5 B4 B3 B2 B1 B0
DEFAULT 0 0 0 0 0 0 0 0
INPUT VOLTAGE
VAINP - VAINN
DIGITAL OUTPUT CODE FOR BIPOLAR RANGES
OFFSET BINARY FORMAT TWO’S COMPLEMENT FORMAT
≥ VREF 0x3FFFF 0x1FFFF
0x3FFFE 0x1FFFE
0x2000 0x00001
0 0x20000 0x00000
0x1FFFF 0x3FFFF
0x00001 0x20001
≤ -VREF 0x00000 0x20000
REF 17
1
V1
21
×−
−
REF
17
V
21
−
REF
17
V
21
−
−
REF 17
1
V1
21
− ×−
−
23Maxim Integrated
18-Bit, Single-Channel, Ultra-Low-Power, Delta-
Sigma ADCs with Programmable Gain and GPIO
MAX11209/MAX11211
SCOC: Self-Calibration Offset Register
The self-calibration offset register is a 24-bit read/write register. The data written/read to/from this register is clocked
in/out MSB first. This register holds the self-calibration offset value. The format is always in two’s complement binary
format. A write to the self-calibration offset register is allowed. The written value remains valid until it is either rewritten
or until an on-demand self-calibration operation is performed, which overwrites the user-supplied value.
The self-calibration offset value is subtracted from each conversion result provided the NOSCO bit in the CTRL3 reg-
ister is set to 0. The self-calibration offset value is subtracted from the conversion result before the self-calibration gain
correction and before the system offset and gain correction. The self-calibration offset value is also applied prior to the
2x scale factor associated with unipolar mode.
Table 18. SGC Register (Read/Write)
Table 19. SCOC Register (Read/Write)
SGC: System Gain Calibration Register
The system gain calibration register is a 24-bit read/write register. The data written/read to/from this register is clocked
in/out MSB first. This register holds the system gain calibration value. The format is always in two’s complement binary
format. A write to the system-calibration register is allowed. The written value remains valid until it is either rewritten or
until an on-demand system-calibration operation is performed, which overwrites the user-supplied value.
The system gain calibration value is used to scale the offset corrected conversion result, provided the NOSYSG bit
in the CTRL3 register is set to 0. The system gain calibration value scales the offset-corrected result by up to 2x or
corrects a gain error of approximately -50%. The amount of positive gain error that can be corrected is determined by
modulator overload characteristics, which can be as much as +25%. The gain is corrected to within 2 LSB.
BIT B23 B22 B21 B20 B19 B18 B17 B16
DEFAULT 00000000
BIT B15 B14 B13 B12 B11 B10 B9 B8
DEFAULT 0 0 0 0 0 0 0 0
BIT B7 B6 B5 B4 B3 B2 B1 B0
DEFAULT 0 0 0 0 0 0 0 0
BIT B23 B22 B21 B20 B19 B18 B17 B16
DEFAULT 00000000
BIT B15 B14 B13 B12 B11 B10 B9 B8
DEFAULT 0 0 0 0 0 0 0 0
BIT B7 B6 B5 B4 B3 B2 B1 B0
DEFAULT 0 0 0 0 0 0 0 0
24 Maxim Integrated
18-Bit, Single-Channel, Ultra-Low-Power, Delta-
Sigma ADCs with Programmable Gain and GPIO
MAX11209/MAX11211
Table 20. SCGC Register (Read/Write)
SCGC: Self-Calibration Gain Register
The self-calibration gain register is a 24-bit read/write register. The data written/read to/from this register is clocked
in/out MSB first. This register holds the self-calibration gain calibration value. The format is always in two’s complement
binary format. A write to the self-calibration register is allowed. The written value remains valid until it is either rewritten
or until an on-demand self-calibration operation is performed, which overwrites the user-supplied value. Any attempt
to write to this register during an active calibration operation is ignored.
The self-calibration gain value is used to scale the self-calibration offset corrected conversion result before the system
offset and gain calibration values have been applied, provided the NOSCG bit in the CTRL3 register is set to 0. The
self-calibration gain value scales the self-calibration offset corrected conversion result by up to 2x or can correct a gain
error of approximately -50%. The gain is corrected to within 2 LSB.
Table 21. Data Rates for All Combinations of RATE[2:0] (LINEF = 0)
Table 22. Data Rates for All Combinations of RATE[2:0] (LINEF = 1)
BIT B23 B22 B21 B20 B19 B18 B17 B16
DEFAULT 00000000
BIT B15 B14 B13 B12 B11 B10 B9 B8
DEFAULT 0 0 0 0 0 0 0 0
BIT B7 B6 B5 B4 B3 B2 B1 B0
DEFAULT 0 0 0 0 0 0 0 0
RATE[2:0] SINGLE-CYCLE DATA RATE (sps) CONTINUOUS DATA RATE (sps)
000 1 —
001 2.5 —
010 5 —
011 10 —
100 15 60
101 30 120
110 60 240
111 120 480
RATE[2:0] SINGLE-CYCLE DATA RATE (sps) CONTINUOUS DATA RATE (sps)
000 0.833 —
001 2.08 —
010 4.17 —
011 8.33 —
100 12.5 50
101 25 100
110 50 200
111 100 400
25Maxim Integrated
18-Bit, Single-Channel, Ultra-Low-Power, Delta-
Sigma ADCs with Programmable Gain and GPIO
MAX11209/MAX11211
Figure 8. RTD Temperature Measurement Circuit
Figure 9. Resistive Bridge Measurement Circuit
Applications Information
See Figure 8 for the RTD temperature measurement circuit
and Figure 9 for a resistive bridge measurement circuit.
Adding more active circuitry to the analog input signal
path is not always the best solution to a small-signal
problem. Sometimes, increasing the dynamic range of
an active device can lead to a simpler solution that also
helps power consumption and linearity.
Often, circuit designers immediately look for an exter-
nal op amp or programmable gain amplifier (PGA)
when confronted with coupling low-amplitude signals
to sampled digital systems. In many cases, choosing
an ADC with more dynamic range and better low-noise
performance yields a solution that works better, simpler,
and with less power.
One such example is measurements from a strain gauge
in a Wheatstone bridge configuration. Assuming a dif-
ferential output signal from the bridge in Figure 10, the
bridge’s output voltage varies from 5mV to 105mV,
while the noise of the bridge itself limits the sensitivity
to approximately 1FV. This gives approximately 100,000
discrete levels that are available for quantization, a feat
accomplished quite well with any ADC having 17 bits or
more of usable resolution. However, as it is not likely that
a 19-bit ADC will have an input range of 105mV, a gain
stage is needed to boost the signal to span the input
range of the ADC (typically between 3V and 5V).
This solution requires finding an amplifier and associated
passives that meet the overall system noise and linearity
needs. Also, the power consumed in the gain stage may
equal or surpass that of the ADC itself, a fact that is sig-
nificant in systems where power consumption is severely
constrained, such as portable sensors or 4–20mA loops.
The low-noise floor of the MAX11209 family of 16-/18-/20-
bit devices gives the designer the ability to use simple
binary shifting (digital gain) of the data word to align the
sample range with the available code space. Digital gain
is internally available in the MAX11209.
IREF2
IREF1
IREF1 = K x IREF2
REFP
REFN
RREF
AINP
AINN
GND
RRTD
MAX11209
MAX11211
REFP
AVDD
REFN
AINP
AINN
MAX11209
MAX11211
26 Maxim Integrated
18-Bit, Single-Channel, Ultra-Low-Power, Delta-
Sigma ADCs with Programmable Gain and GPIO
MAX11209/MAX11211
Chip Information
PROCESS: BiCMOS
Package Information
For the latest package outline information and land patterns, go
to www.maximintegrated.com/packages. Note that a “+”, “#”,
or “-” in the package code indicates RoHS status only. Package
drawings may show a different suffix character, but the drawing
pertains to the package regardless of RoHS status.
Figure 10. The MAX11209 ADC Eliminates an External Gain
Stage.
MAX11209
AVDD
AVDD
18-BIT ADC
AINP
AINN
RSTRAIN
RSTRAIN
PACKAGE
TYPE
PACKAGE
CODE
OUTLINE
NO.
LAND
PATTERN
NO.
16 QSOP E16+4 21-0055 90-0167
Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent
licenses are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and
max limits) shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
Maxim Integrated 160 Rio Robles, San Jose, CA 95134 USA 1-408-601-1000 27
© 2012 Maxim Integrated Products, Inc. Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.
18-Bit, Single-Channel, Ultra-Low-Power, Delta-
Sigma ADCs with Programmable Gain and GPIO
MAX11209/MAX11211
Revision History
REVISION
NUMBER
REVISION
DATE DESCRIPTION PAGES
CHANGED
0 8/10 Initial release —
