EVALUATION KIT AVAILABLE
MAX11108
Tiny, 2.1mm x 1.6mm, 3Msps,
Low-Power, Serial 12-Bit ADC
General Description
Benefits and Features
The MAX11108 features a single-ended analog input
connected to the ADC core. The device also includes a
separate supply input for data interface and a dedicated
input for reference voltage.
●● Low Power Consumption Extends Battery Life
• 6.6mW at 3Msps
• Very Low Power Consumption at 2.5μA/ksps
• 1.3μA Power-Down Current
• 2.2V to 3.6V Supply Voltage
The MAX11108 is a tiny (2.1mm x 1.6mm), 12-bit, compact, high-speed, low-power, successive approximation
analog-to-digital converter (ADC). This high-performance
ADC includes a high-dynamic range sample-and-hold
and a high-speed serial interface. This ADC accepts a
full-scale input from 0V to the power supply or to the reference voltage.
●● Compact ADC Saves Space
• Single-Ended Analog Input 12-Bit Resolution ADC
• 3Msps Conversion Rate with No Pipeline Delay
• 73dB SNR
• 10-Pin, Ultra-TQFN (μDFN), 2.1mm x 1.6mm
Package
The MAX11108 "communicates" from 1.5V to VDD and
operates from a 2.2V to 3.6V supply. The device consumes only 6.6mW at 3Msps and includes full powerdown mode and fast wake-up for optimal power management and a high-speed 3-wire serial interface. The
3-wire serial interface directly connects to SPI/QSPI™/
MICROWIRE® devices without external logic.
●● Variable I/O Voltage Range of 1.5V to 3.6V Eases
Interface to Microcontrollers
Excellent dynamic performance, low voltage, low power,
ease of use, and extremely small package size make this
converter ideal for portable battery-powered data-acquisition applications, and for other applications that demand
low-power consumption and minimal space.
Functional Diagram
The MAX11108 is available in an ultra-TQFN (2.1mm x
1.6mm) package, and operates over the -40°C to +125°C
temperature range.
●● SPI-/QSPI-/MICROWIRE-Compatible Serial Interface
Directly Connects to 1.5V, 1.8V, 2.5V, or 3V Digital
System
VOVDD
CS
SCLK
CONTROL
LOGIC
VDD
MAX11108
Applications
●●
●●
●●
●●
●●
●●
Instrument Data Acquisition
Mobile
Portable Data Logging
Medical Instrumentation
Battery-Operated Systems
Communication Systems
AIN
QSPI is a trademark of Motorola, Inc.
MICROWIRE is a registered trademark of National
Semiconductor Corp.
µMAX is a registered trademark of Maxim Integrated Products, Inc.
19-6227; Rev 3; 3/15
OUTPUT
BUFFER
SAR
CDAC
VREF
AGND
DOUT
MAX11108
Tiny, 2.1mm x 1.6mm, 3Msps,
Low-Power, Serial 12-Bit ADC
Absolute Maximum Ratings
VDD to AGND...........................................................-0.3V to +4V
REF, OVDD, AIN to AGND.......................... -0.3V to the lower of
.............................................................. (VDD + 0.3V) and +4V
CS, SCLK, DOUT TO AGND...................... -0.3V to the lower of
(VOVDD + 0.3V) and +4V
Input/Output Current (all pins).............................................50mA
Continuous Power Dissipation (TA = +70°C)
Ultra TQFN (derate 9mW/°C above +70°C).................722mW
Operating Temperature Range......................... .-40°C to +125°C
Junction Temperature.......................................................+150°C
Storage Temperature Range............................. -65°C to +150°C
Lead Temperature (soldering, 10s).................................. +300°C
Soldering Temperature (reflow)........................................+260°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.
Package Thermal Characteristics (Note 1)
Ultra TQFN
Junction-to-Ambient Thermal Resistance (θJA)..........110.8°C/W
Junction-to-Case Thermal Resistance (θJC).............62.1°C/W
Note 1: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-layer
board. For detailed information on package thermal considerations, refer to www.maximintegrated.com/thermal-tutorial.
Electrical Characteristics
(VDD = 2.2V to 3.6V, VREF = VDD, VOVDD = VDD. fSCLK = 48MHz, 50% duty cycle, 3Msps. CDOUT = 10pF, TA = -40°C to +125°C,
unless otherwise noted. Typical values are at TA = +25°C.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
DC ACCURACY
Resolution
12
Integral Nonlinearity
INL
Differential Nonlinearity
DNL
Offset Error
OE
Gain Error
GE
Total Unadjusted Error
TUE
Bits
No missing codes
Excluding offset and reference errors
±1
LSB
±1
LSB
±0.3
±3
LSB
±1
±3
LSB
±1.5
LSB
DYNAMIC PERFORMANCE (fAIN = 1MHz)
Signal-to-Noise and Distortion
Signal-to-Noise Ratio
Total Harmonic Distortion
Spurious-Free Dynamic Range
Intermodulation Distortion
SINAD
70
72
dB
SNR
70.5
72
dB
THD
-85
SFDR
IMD
76
f1 = 1.0003MHz, f2 = 0.99955MHz
-75
dB
85
dB
-84
dB
Full-Power Bandwidth
-3dB point
40
MHz
Full-Linear Bandwidth
SINAD > 68dB
2.5
MHz
45
MHz
Small-Signal Bandwidth
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Maxim Integrated │ 2
MAX11108
Tiny, 2.1mm x 1.6mm, 3Msps,
Low-Power, Serial 12-Bit ADC
Electrical Characteristics (continued)
(VDD = 2.2V to 3.6V, VREF = VDD, VOVDD = VDD. fSCLK = 48MHz, 50% duty cycle, 3Msps. CDOUT = 10pF, TA = -40°C to +125°C,
unless otherwise noted. Typical values are at TA = +25°C.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
3
Msps
CONVERSION RATE
Throughput
0.03
Conversion Time
260
Acquisition Time
tACQ
Aperture Delay
52
From CS falling edge
ns
4
Aperture Jitter
Serial-Clock Frequency
ns
ns
15
fCLK
0.48
Input Voltage Range
VAIN
0
Input Leakage Current
IILA
ps
48
MHz
ANALOG INPUT (AIN)
Input Capacitance
CAIN
0.002
Track
20
Hold
5
VREF
V
±1
µA
pF
EXTERNAL REFERENCE INPUT (REF)
Reference Input-Voltage Range
Reference Input Leakage
Current
Reference Input Capacitance
DIGITAL INPUTS (SCLK, CS)
VREF
IILR
VIH
Digital Input Low Voltage
VIL
Digital Input Leakage Current
Digital Input Capacitance
Conversion stopped
0.005
CREF
Digital Input High Voltage
Digital Input Hysteresis
1
V
±1
µA
5
pF
0.75 ×
VOVDD
V
0.25 ×
VOVDD
0.15 ×
VOVDD
VHYST
IIL
VDD +
0.05
Inputs at GND or VDD
0.001
CIN
V
V
±1
2
µA
pF
DIGITAL OUTPUT (DOUT)
Output High Voltage
VOH
ISOURCE = 1mA
Output Low Voltage
VOL
ISINK = 5µA
High-Impedance Leakage
Current
IOL
High-Impedance Output
Capacitance
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COUT
0.85 ×
VOVDD
V
4
0.15 ×
VOVDD
V
±1.0
µA
pF
Maxim Integrated │ 3
MAX11108
Tiny, 2.1mm x 1.6mm, 3Msps,
Low-Power, Serial 12-Bit ADC
Electrical Characteristics (continued)
(VDD = 2.2V to 3.6V, VREF = VDD, VOVDD = VDD. fSCLK = 48MHz, 50% duty cycle, 3Msps. CDOUT = 10pF, TA = -40°C to +125°C,
unless otherwise noted. Typical values are at TA = +25°C.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
POWER SUPPLY
Positive Supply Voltage
Digital I/O Supply Voltage
Positive Supply Current
(Full-Power Mode)
Positive Supply Current (FullPower Mode), No Clock
VDD
2.2
3.6
V
VOVDD
1.5
VDD
V
IVDD
VAIN = VGND
3.3
IOVDD
VAIN = VGND
0.33
IVDD
Power-Down Current
IPD
Line Rejection
1.98
Leakage only
1.3
VDD = 2.2V to 3.6V, VREF = 2.2V
0.7
mA
mA
10
µA
LSB/V
TIMING CHARACTERISTICS (Note 2)
Quiet Time
tQ
(Note 3)
4
ns
CS Pulse Width
t1
(Note 3)
10
ns
CS Fall to SCLK Setup
t2
(Note 3)
5
ns
CS Falling Until DOUT HighImpedance Disabled
t3
(Note 3)
1
ns
Data Access Time After SCLK
Falling Edge
t4
SCLK Pulse Width Low
t5
Percentage of clock period (Note 3)
40
60
%
SCLK Pulse Width High
t6
Percentage of clock period (Note 3)
40
60
%
Data Hold Time From SCLK
Falling Edge
t7
Figure 3 (Note 3)
5
SCLK Falling Until DOUT HighImpedance
t8
Figure 4 (Note 3)
2.5
Power-Up Time
Figure 2, VOVDD = 2.2V to 3.6V
15
Figure 2, VOVDD = 1.5V to 2.2V
16.5
Conversion cycle (Note 3)
ns
ns
14
ns
1
Cycle
Note 2: All timing specifications given are with a 10pF capacitor.
Note 3: Guaranteed by design in characterization; not production tested.
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Maxim Integrated │ 4
MAX11108
Tiny, 2.1mm x 1.6mm, 3Msps,
Low-Power, Serial 12-Bit ADC
SAMPLE
SAMPLE
t6
CS
t1
t5
t2
SCLK
DOUT
16
1
2
0
HIGH
IMPEDANCE
3
D11
4
D10
5
D9
6
D8
7
D7
8
D6
9
10
D5
D4
11
D3
12
D2
13
D1
14
D0
15
0
16
0
HIGH
IMPEDANCE
(MSB)
t3
t4
t7
1
t8 tQUIET
tCONVERT
tACQ
1/fSAMPLE
Figure 1. Interface Signals for Maximum Throughput
t7
t4
SCLK
SCLK
VIH
DOUT
OLD DATA
NEW DATA
VIL
Figure 2. Setup Time After SCLK Falling Edge
VIH
DOUT
OLD DATA
NEW DATA
VIL
Figure 3. Hold Time After SCLK Falling Edge
t8
SCLK
DOUT
HIGH IMPEDANCE
Figure 4. SCLK Falling Edge DOUT Three-State
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Maxim Integrated │ 5
MAX11108
Tiny, 2.1mm x 1.6mm, 3Msps,
Low-Power, Serial 12-Bit ADC
Typical Operating Characteristics
(TA = +25°C, unless otherwise noted.)
-0.5
0
-0.5
MAX11108 toc03
0.5
DNL (LSB)
0
fS = 3.0Msps
OFFSET ERROR vs. TEMPERATURE
2.0
1.5
OFFSET ERROR (LSB)
fS = 3.0Msps
0.5
INL (LSB)
1.0
MAX11108 toc01
1.0
DIFFERENTIAL NONLINEARITY
vs. DIGITAL OUTPUT CODE
MAX11108 toc02
INTEGRAL NONLINEARITY
vs. DIGITAL OUTPUT CODE
1.0
0.5
0
-0.5
-1.0
-1.5
1000
2000
3000
-1.0
4000
1000
0
DIGITAL OUTPUT CODE
MAX11108 toc04
0.8
0.6
0.2
TEMPERATURE (°C)
35,000
HISTOGRAM FOR 30,000 CONVERSIONS
30,000
20,000
0
15,000
-0.2
-0.4
10,000
-0.6
5000
-0.8
0
-40 -25 -10 5 20 35 50 65 80 95 110 125
2047
2046
SNR AND SINAD
vs. ANALOG INPUT FREQUENCY
fS = 3Msps
SNR
2050
-80
73
72
fS = 3Msps
-70
THD (dB)
SNR AND SINAD (dB)
74
2049
THD vs. ANALOG INPUT FREQUENCY
-60
MAX11108 toc06
75
2048
DIGITAL CODE OUTPUT
TEMPERATURE (°C)
SINAD
-90
-100
71
70
-40 -25 -10 5 20 35 50 65 80 95 110 125
25,000
0.4
-1.0
-2.0
4000
CODE COUNT
GAIN ERROR (LSB)
3000
DIGITAL OUTPUT CODE
GAIN ERROR vs. TEMPERATURE
1.0
2000
MAX11108 toc05
0
MAX11108 toc07
-1.0
-110
0
300
600
900
fIN (kHz)
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1200
1500
-120
0
300
600
900
1200
1500
fIN (kHz)
Maxim Integrated │ 6
MAX11108
Tiny, 2.1mm x 1.6mm, 3Msps,
Low-Power, Serial 12-Bit ADC
Typical Operating Characteristics (continued)
(TA = +25°C, unless otherwise noted.)
fS = 3Msps
120
THD (dB)
100
-85
90
-90
80
-95
300
600
900
1200
0
20
40
60
80
fIN (kHz)
RIN (Ω)
1MHz SINE-WAVE INPUT
(16,834-POINT FFT PLOT)
REFERENCE CURRENT
vs. SAMPLING RATE
fS = 3.0Msps
fIN = 1.0183MHz
-20
-100
1500
200
100
MAX11108 toc11
0
MAX11108 toc10
150
-40
-60
IREF (µA)
SFDR (dB)
-80
0
AMPLITUDE (dB)
fS = 3.0Msps
fIN = 1.0183MHz
-75
110
70
THD vs. INPUT RESISTANCE
-70
MAX11108 toc09
SFDR vs. ANALOG INPUT FREQUENCY
MAX11108 toc08
130
AHD3 = -122.7dB
100
AHD2 = -109.5dB
-80
50
-100
0
250
500
750
1000
1250
0
1500
500
0
1000
ANALOG SUPPLY CURRENT
vs. TEMPERATURE
VDD = 3.6V
2.9
2.6
VDD = 3.0V
2.3
2.0
73.0
SNR (dB)
IVDD (mA)
3.2
73.5
MAX11108 toc12
3.5
1500
2000
2500
3000
fS (ksps)
FREQUENCY (kHz)
SNR vs. REFERENCE VOLTAGE
MAX11108 toc13
-120
fS = 3Msps
fIN = 1.0183MHz
72.5
72.0
71.5
VDD = 2.2V
-40 -25 -10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
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71.0
2.2
2.4
2.6
2.8 3.0
VREF (V)
3.2
3.4
3.6
Maxim Integrated │ 7
MAX11108
Tiny, 2.1mm x 1.6mm, 3Msps,
Low-Power, Serial 12-Bit ADC
Pin Configuration
TOP VIEW
AGND
SCLK
DOUT
OVDD
CS
9
8
7
6
MAX11108
10
+
5
1
2
3
4
AIN
AGND
REF
VDD
AGND
ULTRA TQFN
(2.1mm x 1.6mm)
Pin Description
PIN
1
NAME
AIN
FUNCTION
Analog Single-Ended Input
2, 5, 10
AGND
3
REF
Reference Input Pin
4
VDD
Positive Supply Voltage
6
CS
Chip Select (Active Low). Initiates acquisition on the falling edge.
7
OVDD
Digital I/O Supply Voltage (CS, DOUT, SCLK).
8
DOUT
Serial Data Output. DOUT changes state on SCLK’s falling edge. See Figures 1 to 4 for details.
9
SCLK
Serial Clock Input. SCLK drives the conversion process and clocks data out. See Figures 1 to 4 for
details.
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Ground. This pin must connect to a solid ground plane.
Maxim Integrated │ 8
MAX11108
Tiny, 2.1mm x 1.6mm, 3Msps,
Low-Power, Serial 12-Bit ADC
Typical Operating Circuit
VDD
VOVDD
+3V
+3V
REF
REFERENCE INPUT
+3V
ANALOG
INPUT
MAX11108
SCLK
SCK
DOUT
MISO
CS
AIN
CPU
SS
AGND
Detailed Description
The MAX11108 is a tiny, fast, 12-bit, low-power, singlesupply ADC. This device “communicates” from 1.5V to
VDD, operates from a 2.2V to 3.6V supply, and consumes
only 9mW (VDD = 3V)/6.6mW (VDD = 2.2V) at 3Msps.
This 3Msps device is capable of sampling at full rate when
driven by a 48MHz clock.
The conversion result appears at DOUT, MSB first, with a
leading zero followed by the 12-bit result. A 12-bit result is
followed by two trailing zeros (see Figure 1).
The device features a dedicated reference input (REF).
The input signal range for AIN is defined as 0V to VREF
with respect to AGND.
This ADC includes a power-down feature allowing
minimized power consumption at 2.5µA/ksps for lower
throughput rates. The wake-up and power-down feature is
controlled by using the SPI interface as described in the
Operating Modes section.
Serial Interface
This device features a 3-wire serial interface that directly
connects to SPI/QSPI/MICROWIRE devices without
external logic. Figure 1 shows the interface signals for
a single conversion frame to achieve maximum throughput.
The falling edge of CS defines the sampling instant.
Once CS transitions low, the external clock signal
(SCLK) controls the conversion.
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The SAR core successively extracts binary-weighted
bits in every clock cycle. The MSB appears on the data
bus during the 2nd clock cycle with a delay outlined in
the timing specifications. All extracted data bits appear
successively on the data bus with the LSB appearing
during the 13th clock cycle for 12-bit operation. The
serial data stream of conversion bits is preceded by a
leading “zero” and succeeded by trailing “zeros.” The data
output (DOUT) goes into high-impedance state during the
16th clock cycle.
To sustain the maximum sample rate, the device has to
be resampled immediately after the 16th clock cycle. For
lower sample rates, the CS falling edge can be delayed
leaving DOUT in a high-impedance condition. Pull CS
high after the 10th SCLK falling edge (see the Operating
Modes section).
Analog Input
The ADC produces a digital output that corresponds to the
analog input voltage within the specified operating range
of 0 to VREF.
Figure 5 shows an equivalent circuit for the analog input
AIN. Internal protection diodes D1/D2 confine the analog
input voltage within the power rails (VDD, AGND). The
analog input voltage can swing from (AGND - 0.3V) to
(VDD + 0.3V) without damaging the device.
The electric load presented to the external stage driving the analog input varies depending on which mode
the ADC is in: track mode vs. conversion mode. In track
mode, the internal sampling capacitor CS (16pF) has
Maxim Integrated │ 9
MAX11108
Tiny, 2.1mm x 1.6mm, 3Msps,
Low-Power, Serial 12-Bit ADC
Operating Modes
to be charged through the resistor R (50Ω) to the input
voltage. For faithful sampling of the input, the capacitor
voltage on CS has to settle to the required accuracy during the track time.
The IC offers two modes of operation: normal mode and
power-down mode. The logic state of the CS signal during a conversion activates these modes. The power-down
mode can be used to optimize power dissipation with
respect to sample rate.
The source impedance of the external driving stage in
conjunction with the sampling switch resistance affects
the settling performance. The THD vs. Input Resistance
graph in the Typical Operating Characteristics shows
THD sensitivity as a function of the signal source impedance. Keep the source impedance at a minimum for highdynamic performance applications. Use a high-performance op amp such as the MAX4430 to drive the analog
input, thereby decoupling the signal source and the ADC.
Normal Mode
In normal mode, the device is powered up at all times,
thereby achieving its maximum throughput rates. Figure
6 shows the timing diagram in normal mode. The falling
edge of CS samples the analog input signal, starts a conversion, and frames the serial data transfer.
To remain in normal mode, keep CS low until the falling
edge of the 10th SCLK cycle. Pulling CS high after the
10th SCLK falling edge keeps the part in normal mode.
However, pulling CS high before the 10th SCLK falling
edge terminates the conversion, DOUT goes into highimpedance mode, and the device enters power-down
mode. See Figure 7.
While the ADC is in conversion mode, the sampling
switch is open presenting a pin capacitance, CP
(CP = 5pF), to the driving stage. See the Applications
Information section for information on choosing an appropriate buffer for the ADC.
ADC Transfer Function
The output format is straight binary. The code transitions midway between successive integer LSB values
such as 0.5 LSB, 1.5 LSB, etc. The LSB size is VREF/2n
where n = 12. The ideal transfer characteristic is shown
in Figure 9.
VDD
Power-Down Mode
In power-down mode, all bias circuitry is shut down drawing typically only 1.3µA of leakage current. To save power,
put the device in power-down mode between conversions. Using the power-down mode between conversions
is ideal for saving power when sampling the analog input
infrequently.
Entering Power-Down Mode
SWITCH CLOSED IN TRACK MODE
SWITCH OPEN IN CONVERSION MODE
D1
To enter power-down mode, drive CS high between the
2nd and 10th falling edges of SCLK (see Figure 7). By
pulling CS high, the current conversion terminates and
DOUT enters high impedance.
CS
R
AIN
CP
D2
Figure 5. Analog Input Circuit
KEEP CS LOW UNTIL AFTER THE 10TH SCLK FALLING EDGE
PULL CS HIGH AFTER THE 10TH SCLK FALLING EDGE
CS
SCLK
DOUT
1
2
HIGH
IMPEDANCE
3
4
5
6
7
8
VALID DATA
9
10
11
12
13
14
15
16
HIGH
IMPEDANCE
Figure 6. Normal Mode
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Maxim Integrated │ 10
MAX11108
Tiny, 2.1mm x 1.6mm, 3Msps,
Low-Power, Serial 12-Bit ADC
PULL CS HIGH AFTER THE 2ND AND BEFORE THE 10TH SCLK FALLING EDGE
CS
SCLK
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
DOUT
HIGH
IMPEDANCE
INVALID
DATA
INVALID DATA OR HIGH IMPEDANCE
HIGH IMPEDANCE
Figure 7. Entering Power-Down Mode
CS
1
SCLK
2
3
4
DOUT
5
6
7
8
9
10
11
12
13
14
15
INVALID DATA (DUMMY CONVERSION)
HIGH
IMPEDANCE
16
N
1
HIGH
IMPEDANCE
2
3
4
5
6
7
8
9
10
11
12
13
VALID DATA
14
15
16
HIGH
IMPEDANCE
Figure 8. Exiting Power-Down Mode
Exiting Power-Down Mode
OUTPUT CODE
To exit power-down mode, implement one dummy conversion by driving CS low for at least 10 clock cycles (see
Figure 8). The data on DOUT is invalid during this dummy
conversion. The first conversion following the dummy
cycle contains a valid conversion result.
FS - 1.5 x LSB
111...111
111...110
111...101
The power-up time equals the duration of the dummy
cycle, and is dependent on the clock frequency. The power-up time for 3Msps operation (48MHz SCLK) is 333ns.
Supply Current vs. Sampling Rate
000...010
000...001
000...000
0
1
2
3
0.5 x LSB
Figure 9. ADC Transfer Function
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2n-2 2n-1 2n
ANALOG
INPUT (LSB)
FULL SCALE (FS):
AIN = VREF
n = RESOLUTION
For applications requiring lower throughput rates, the
user can reduce the clock frequency (fSCLK) to lower the
sample rate. Figure 10 shows the typical supply current
(IVDD) as a function of sample rate (fS). The part operates
in normal mode and is never powered down.
The user can also power down the ADC between conversions by using the power-down mode. Figure 11 shows
that as the sample rate is reduced, the device remains in
the power-down state longer and the average supply current (IVDD) drops accordingly.
Maxim Integrated │ 11
MAX11108
Tiny, 2.1mm x 1.6mm, 3Msps,
Low-Power, Serial 12-Bit ADC
14-Cycle Conversion Mode
The ICs can operate with 14 cycles per conversion.
Figure 12 shows the corresponding timing diagram.
Observe that DOUT does not go into high-impedance
mode. Also, observe that tACQ needs to be sufficiently
long to guarantee proper settling of the analog input
voltage. See the Electrical Characteristics table for tACQ
requirements and the Analog Input section for a description of the analog inputs.
Applications Information
Layout, Grounding, and Bypassing
For best performance, use PCBs with a solid ground
plane. Ensure that digital and analog signal lines are
separated from each other. Do not run analog and digital
(especially clock) lines parallel to one another or digital
lines underneath the ADC package. Noise in the VDD
power supply, OVDD, and REF affects the ADC’s performance. Bypass the VDD, OVDD, and REF to ground with
0.1µF and 10µF bypass capacitors. Minimize capacitor
lead and trace lengths for best supply-noise rejection.
Choosing an Input Amplifier
It is important to match the settling time of the input
amplifier to the acquisition time of the ADC. The conversion results are accurate when the ADC samples the
input signal for an interval longer than the input signal’s
worst-case settling time. By definition, settling time is
the interval between the application of an input voltage
VDD = 3V
fSCLK = VARIABLE
16 CYCLES/CONVERSION
For devices using an external reference, the choice of
the reference determines the output accuracy of the
ADC. An ideal voltage reference provides a perfect initial
accuracy and maintains the reference voltage independent of changes in load current, temperature, and time.
Considerations in selecting a reference include initial
voltage accuracy, temperature drift, current source, sink
capability, quiescent current, and noise. Figure 13 shows
a typical application circuit using the MAX6126 to provide
the reference voltage. The MAX6033 and MAX6043 are
also excellent choices.
3.0
VDD = 3V
fSCLK = 48MHz
2.5
2.0
3
2
1.5
1.0
1
0
Choosing a Reference
IVDD (mA)
IVDD (mA)
4
Figure 13 shows a typical application circuit. The
MAX4430, offering a settling time of 37ns at 16 bits, is
an excellent choice for this application. See the THD
vs. Input Resistance graph in the Typical Operating
Characteristics.
MAX11102 fig11
5
step and the point at which the output signal reaches
and stays within a given error band centered on the
resulting steady-state amplifier output level. The ADC
input sampling capacitor charges during the sampling
cycle, referred to as the acquisition period. During this
acquisition period, the settling time is affected by the
input resistance and the input sampling capacitance. This
error can be estimated by looking at the settling of an RC
time constant using the input capacitance and the source
impedance over the acquisition time period.
0.5
0
500
1000
1500
2000
2500
3000
fS (ksps)
Figure 10. Supply Current vs. Sample Rate (Normal Operating
Mode, 3Msps Devices)
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0
0
200
400
600
800
1000
fS (ksps)
Figure 11. Supply Current vs. Sample Rate (Device Powered
Down Between Conversions, 3Msps Devices)
Maxim Integrated │ 12
MAX11108
Tiny, 2.1mm x 1.6mm, 3Msps,
Low-Power, Serial 12-Bit ADC
SAMPLE
SAMPLE
CS
SCLK
2
1
DOUT
3
D11
0
4
D10
5
D9
6
D8
7
8
D7
9
D6
D5
10
D4
11
D3
12
D2
13
14
D1
D0
(MSB)
1
0
0
tACQ
1/fSAMPLE
tCONVERT
Figure 12. 14-Clock Cycle Operation
+5V
10µF
0.1µF
3V
100pF COG
3V
VDD
500Ω
VSOURCE
500Ω
VDC
0.1µF
10µF
MAX4430
3
-5V
2
0.1µF
10Ω
1
10µF
0.1µF
AGND
5
4
OVDD
AIN
470pF
COG CAPACITOR
MAX11108
10µF
SCLK
SCK
DOUT
MISO
CS
SS
CPU
REF
0.1µF
10µF
EP
3V
+5V
7
6
0.1µF
4
3
OUTF
IN
2
1µF
OUTS
MAX6126
GNDS
GND
NR
0.1µF
1
0.1µF
Figure 13. Typical Application Circuit
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Maxim Integrated │ 13
MAX11108
Definitions
Integral Nonlinearity
Integral nonlinearity (INL) is the deviation of the values on
an actual transfer function from a straight line. For these
devices, the straight line is a line drawn between the end
points of the transfer function after offset and gain errors
are nulled.
Differential Nonlinearity
Differential nonlinearity (DNL) is the difference between
an actual step width and the ideal value of 1 LSB. A DNL
error specification of ±1 LSB or less guarantees no missing codes and a monotonic transfer function.
Offset Error
The deviation of the first code transition (00 . . . 000) to
(00 . . . 001) from the ideal, that is, AGND + 0.5 LSB.
Gain Error
The deviation of the last code transition (111 . . . 110) to
(111 . . . 111) from the ideal after adjusting for the offset
error, that is, VREF - 1.5 LSB.
Aperture Jitter
Aperture jitter (tAJ) is the sample-to-sample variation in
the time between the samples.
Aperture Delay
Aperture delay (tAD) is the time between the falling edge
of sampling clock and the instant when an actual sample
is taken.
Signal-to-Noise Ratio (SNR)
SNR is a dynamic figure of merit that indicates the converter’s noise performance. For a waveform perfectly
reconstructed from digital samples, the theoretical maximum SNR is the ratio of the full-scale analog input (RMS
value) to the RMS quantization error (residual error).
The ideal, theoretical minimum analog-to-digital noise is
caused by quantization error only and results directly from
the ADC’s resolution (N bits):
SNR (dB) (MAX) = (6.02 x N + 1.76) (dB)
In reality, there are other noise sources such as thermal
noise, reference noise, and clock jitter that also degrade
SNR. SNR is computed by taking the ratio of the RMS
signal to the RMS noise. RMS noise includes all spectral
components to the Nyquist frequency excluding the fundamental, 2nd to 5th harmonic, and the DC offset.
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Tiny, 2.1mm x 1.6mm, 3Msps,
Low-Power, Serial 12-Bit ADC
Signal-to-Noise Ratio and Distortion
(SINAD)
SINAD is a dynamic figure of merit that indicates the converter’s noise and distortion performance. SINAD is computed by taking the ratio of the RMS signal to the RMS
noise plus distortion. RMS noise plus distortion includes
all spectral components to the Nyquist frequency excluding the fundamental and the DC offset:
SIGNAL RMS
SINAD(dB) = 20 × log
(NOISE + DISTORTION) RMS
Total Harmonic Distortion
Total harmonic distortion (THD) is the ratio of the RMS
sum of the first four harmonics of the input signal to the
fundamental itself. This is expressed as:
V 22 + V32 + V 42 + V52
THD
= 20 × log
V1
where V1 is the fundamental amplitude and V2–V5 are
the amplitudes of the 2nd- through 5th-order harmonics.
Spurious-Free Dynamic Range (SFDR)
SFDR is a dynamic figure of merit that indicates the lowest usable input signal amplitude. SFDR is the ratio of
the RMS amplitude of the fundamental (maximum signal
component) to the RMS value of the next largest spurious
component, excluding DC offset. SFDR is specified in
decibels with respect to the carrier (dBc).
Full-Power Bandwidth
Full-power bandwidth is the frequency at which the input
signal amplitude attenuates by 3dB for a full-scale input.
Full-Linear Bandwidth
Full-linear bandwidth is the frequency at which the signalto-noise ratio and distortion (SINAD) is equal to a specified value.
Intermodulation Distortion
Any device with nonlinearities creates distortion products when two sine waves at two different frequencies
(f1 and f2) are applied into the device. Intermodulation
distortion (IMD) is the total power of the IM2 to IM5 intermodulation products to the Nyquist frequency relative to
the total input power of the two input tones, f1 and f2.
The individual input tone levels are at -6dBFS.
Maxim Integrated │ 14
MAX11108
Tiny, 2.1mm x 1.6mm, 3Msps,
Low-Power, Serial 12-Bit ADC
Ordering Information
PART
PIN-PACKAGE
BITS
SPEED (Msps)
NO. OF CHANNELS
TOP MARK
1
+ABC
MAX11108AVB+T
10 Ultra TQFN
12
3
Note: This device is specified over the -40°C to +125°C operating temperature range.
+Denotes a lead(Pb)-free/RoHS-compliant package.
T = Tape and reel.
Chip Information
PROCESS: BiCMOS
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Package Information
For the latest package outline information and land patterns
(footprints), 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.
PACKAGE
TYPE
PACKAGE
CODE
OUTLINE
NO.
LAND
PATTERN NO.
10 Ultra
TQFN
V101A2CN+1
21-0610
90-0386
Maxim Integrated │ 15
MAX11108
Tiny, 2.1mm x 1.6mm, 3Msps,
Low-Power, Serial 12-Bit ADC
Revision History
REVISION
NUMBER
REVISION
DATE
0
9/12
Initial release
1
4/13
Updated data sheet
2
12/14
Revised Benefits and Features section
1
3
3/15
Removed automotive reference from data sheet
1
DESCRIPTION
PAGES
CHANGED
—
1–4, 8–15
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim Integrated’s website at www.maximintegrated.com.
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 and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.
© 2015 Maxim Integrated Products, Inc. │ 16
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