1
2
3
45
6
7
8
CS SCLK
DOUT
DIN
IN1
VA
GND
IN2
ADC082S021
ADC082S021
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SNAS282D –APRIL 2005–REVISED MARCH 2013
ADC082S021 2 Channel, 50 ksps to 200 ksps, 8-Bit A/D Converter
Check for Samples: ADC082S021
1FEATURES DESCRIPTION
The ADC082S021 is a low-power, two-channel
2• Specified Over a Range of Sample Rates. CMOS 8-bit analog-to-digital converter with a high-
• Two Input Channels speed serial interface. Unlike the conventional
• Variable Power Management practice of specifying performance at a single sample
rate only, the ADC082S021 is fully specified over a
• Single Power Supply with 2.7V - 5.25V Range sample rate range of 50 ksps to 200 ksps. The
converter is based upon a successive-approximation
KEY SPECIFICATIONS register architecture with an internal track-and-hold
• DNL: ±0.04 LSB (typ) circuit. It can be configured to accept one or two input
signals at inputs IN1 and IN2.
• INL: ±0.04 LSB (typ)
• SNR: 49.6 dB (typ) The output serial data is straight binary, and is
compatible with several standards, such as SPI™,
• Power Consumption: QSPI™, MICROWIRE, and many common DSP
– 3V Supply 1.6 mW (typ) serial interfaces.
– 5V Supply 5.8 mW (typ) The ADC082S021 operates with a single supply that
can range from +2.7V to +5.25V. Normal power
APPLICATIONS consumption using a +3V or +5V supply is 1.6 mW
• Portable Systems and 5.8 mW, respectively. The power-down feature
reduces the power consumption to just 0.12 µW using
• Remote Data Acquisition a +3V supply, or 0.35 µW using a +5V supply.
• Instrumentation and Control Systems The ADC082S021 is packaged in an 8-lead VSSOP
package. Operation over the industrial temperature
range of −40°C to +85°C.
Table 1. Pin-Compatible Alternatives by Resolution and Speed(1)
Resolution Specified for Sample Rate Range of:
50 to 200 ksps 200 to 500 ksps 500 ksps to 1 Msps
12-bit ADC122S021 ADC122S051 ADC122S101
10-bit ADC102S021 ADC102S051 ADC102S101
8-bit ADC082S021 ADC082S051 ADC082S101
(1) All devices are fully pin and function compatible.
Connection Diagram
Figure 1. VSSOP Package
See Package Number DGK0008A
1Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
2All trademarks are the property of their respective owners.
PRODUCTION DATA information is current as of publication date. Copyright © 2005–2013, Texas Instruments Incorporated
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
IN1
IN2 MUX T/H
SCLK
VA
GND
CS
DIN
DOUT
CONTROL
LOGIC
8-BIT
SUCCESSIVE
APPROXIMATION
ADC
GND
ADC082S021
SNAS282D –APRIL 2005–REVISED MARCH 2013
www.ti.com
Block Diagram
Pin Descriptions and Equivalent Circuits
Pin No. Pin Name Description
ANALOG I/O
5,4 IN1 and IN2 Analog inputs. These signals can range from 0V to VA.
DIGITAL I/O
8 SCLK Digital clock input. This clock directly controls the conversion and readout processes.
Digital data output. The output samples are clocked out at this pin on falling edges of the
7 DOUT SCLK pin.
Digital data input. The ADC082S021's Control Register is loaded through this pin on rising
6 DIN edges of the SCLK.
Chip select. On the falling edge of CS, a conversion process begins. Conversions continue
1 CS as long as CS is held low.
POWER SUPPLY
Positive supply pin. This pin should be connected to a quiet +2.7V to +5.25V source and
2 VAbypassed to GND with a 1 µF capacitor and a 0.1 µF monolithic capacitor located within 1
cm of the power pin.
3 GND The ground return for the die.
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These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
Absolute Maximum Ratings(1)(2)(3)
Analog Supply Voltage VA−0.3V to 6.5V
Voltage on Any Pin to GND −0.3V to VA+0.3V
Input Current at Any Pin(4) ±10 mA
Package Input Current(4) ±20 mA
Power Consumption at TA= 25°C See(5)
Human Body Model 2500V
ESD Susceptibility(6) Machine Model 250V
Junction Temperature +150°C
Storage Temperature −65°C to +150°C
(1) Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for
which the device is functional, but do not ensure specific performance limits. For ensured specifications and test conditions, see the
Electrical Characteristics. The ensured specifications apply only for the test conditions listed. Some performance characteristics may
degrade when the device is not operated under the listed test conditions.
(2) All voltages are measured with respect to GND = 0V, unless otherwise specified.
(3) If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/ Distributors for availability and
specifications.
(4) When the input voltage at any pin exceeds the power supply (that is, VIN < GND or VIN > VA), the current at that pin should be limited to
10 mA. The 20 mA maximum package input current rating limits the number of pins that can safely exceed the power supplies with an
input current of 10 mA to two. The Absolute Maximum Rating specification does not apply to the VApin. The current into the VApin is
limited by the Analog Supply Voltage specification.
(5) The absolute maximum junction temperature (TJmax) for this device is 150°C. The maximum allowable power dissipation is dictated by
TJmax, the junction-to-ambient thermal resistance (θJA), and the ambient temperature (TA), and can be calculated using the formula
PDMAX = (TJmax −TA)/θJA. The values for maximum power dissipation listed above will be reached only when the device is operated in
a severe fault condition (e.g. when input or output pins are driven beyond the power supply voltages, or the power supply polarity is
reversed). Obviously, such conditions should always be avoided.
(6) Human body model is 100 pF capacitor discharged through a 1.5 kΩresistor. Machine model is 220 pF discharged through zero ohms
Operating Ratings(1)(2)
Operating Temperature Range −40°C ≤TA≤+85°C
VASupply Voltage +2.7V to +5.25V
Digital Input Pins Voltage Range −0.3V to VA
Clock Frequency 50 kHz to 16 MHz
Analog Input Voltage 0V to VA
(1) Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for
which the device is functional, but do not ensure specific performance limits. For ensured specifications and test conditions, see the
Electrical Characteristics. The ensured specifications apply only for the test conditions listed. Some performance characteristics may
degrade when the device is not operated under the listed test conditions.
(2) All voltages are measured with respect to GND = 0V, unless otherwise specified.
Package Thermal Resistance(1)
Package θJA
8-lead VSSOP 250°C / W
(1) Soldering process must comply with Reflow Temperature Profile specifications. Refer to www.ti.com/packaging. Reflow temperature
profiles are different for lead-free and non-lead-free packages.
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ADC082S021 Converter Electrical Characteristics(1)
The following specifications apply for VA= +2.7V to 5.25V, GND = 0V, fSCLK = 0.8 MHz to 3.2 MHz, fSAMPLE = 50 ksps to 200
ksps, CL= 50 pF, unless otherwise noted. Boldface limits apply for TA= TMIN to TMAX: all other limits TA= 25°C.
Parameter Test Conditions Typical Limits(2) Units
STATIC CONVERTER CHARACTERISTICS
Resolution with No Missing Codes 8Bits
INL Integral Non-Linearity ±0.04 ±0.2 LSB (max)
DNL Differential Non-Linearity ±0.04 ±0.2 LSB (max)
VOFF Offset Error +0.52 ±0.7 LSB (max)
OEM Channel to Channel Offset Error Match ±0.01 ±0.3 LSB (max)
FSE Full-Scale Error +0.51 ±0.7 LSB (max)
Channel to Channel Full-Scale Error
FSEM +0.01 ±0.3 LSB (max)
Match
DYNAMIC CONVERTER CHARACTERISTICS
VA= +2.7 to 5.25V
SINAD Signal-to-Noise Plus Distortion Ratio 49.6 49.1 dB (min)
fIN = 39.9 kHz, −0.02 dBFS
VA= +2.7 to 5.25V
SNR Signal-to-Noise Ratio 49.6 49.2 dB (min)
fIN = 39.9 kHz, −0.02 dBFS
VA= +2.7 to 5.25V
THD Total Harmonic Distortion −76 −62 dB (max)
fIN = 39.9 kHz, −0.02 dBFS
VA= +2.7 to 5.25V
SFDR Spurious-Free Dynamic Range 68 63 dB (min)
fIN = 39.9 kHz, −0.02 dBFS
VA= +2.7 to 5.25V
ENOB Effective Number of Bits 7.9 7.9 Bits (min)
fIN = 39.9 kHz, −0.02 dBFS
VA= +5.25V
Channel-to-Channel Crosstalk −73 dB
fIN = 40.2 kHz
Intermodulation Distortion, Second VA= +5.25V −78 dB
Order Terms fa= 40.161 kHz, fb= 41.015 kHz
IMD Intermodulation Distortion, Third Order VA= +5.25V −73 dB
Terms fa= 40.161 kHz, fb= 41.015 kHz
VA= +5V 11 MHz
FPBW -3 dB Full Power Bandwidth VA= +3V 8 MHz
ANALOG INPUT CHARACTERISTICS
VIN Input Range 0 to VAV
IDCL DC Leakage Current ±1 µA (max)
Track Mode 33 pF
CINA Input Capacitance Hold Mode 3 pF
DIGITAL INPUT CHARACTERISTICS
VA= +5.25V 2.4 V (min)
VIH Input High Voltage VA= +3.6V 2.1 V (min)
VIL Input Low Voltage 0.8 V (max)
IIN Input Current VIN = 0V or VIN = VA±10 µA (max)
CIND Digital Input Capacitance 2 4pF (max)
(1) Min/max specification limits are ensured by design, test, or statistical analysis.
(2) Tested limits are ensured to TI's AOQL (Average Outgoing Quality Level).
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ADC082S021 Converter Electrical Characteristics(1) (continued)
The following specifications apply for VA= +2.7V to 5.25V, GND = 0V, fSCLK = 0.8 MHz to 3.2 MHz, fSAMPLE = 50 ksps to 200
ksps, CL= 50 pF, unless otherwise noted. Boldface limits apply for TA= TMIN to TMAX: all other limits TA= 25°C.
Parameter Test Conditions Typical Limits(2) Units
DIGITAL OUTPUT CHARACTERISTICS
ISOURCE = 200 µA VA−0.03 VA−0.5 V (min)
VOH Output High Voltage ISOURCE = 1 mA VA−0.1
ISINK = 200 µA 0.03 0.4 V (max)
VOL Output Low Voltage ISINK = 1 mA 0.1
IOZH, IOZL TRI-STATE Leakage Current ±0.01 ±1 µA (max)
COUT TRI-STATE Output Capacitance 2 4pF (max)
Output Coding Straight (Natural) Binary
POWER SUPPLY CHARACTERISTICS (CL= 10 pF)
2.7 V (min)
VAAnalog Supply Voltage 5.25 V (max)
VA= +5.25V, 1.1 1.7 mA (max)
fSAMPLE = 200 ksps, fIN = 40 kHz
Supply Current, Normal Mode
(Operational, CS low) VA= +3.6V, 0.45 0.8 mA (max)
fSAMPLE = 200 ksps, fIN = 40 kHz
IAVA= +5.25V, 200 nA
fSAMPLE = 0 ksps
Supply Current, Shutdown (CS high) VA= +3.6V, 200 nA
fSAMPLE = 0 ksps
VA= +5.25V 5.8 8.9 mW (max)
Power Consumption, Normal Mode
(Operational, CS low) VA= +3.6V 1.6 2.9 mW (max)
PDVA= +5.25V 1.05 µW
Power Consumption, Shutdown (CS
high) VA= +3.6V 0.72 µW
AC ELECTRICAL CHARACTERISTICS
0.8 MHz (min)
fSCLK Maximum Clock Frequency See(3) 3.2 MHz (max)
50 ksps (min)
fSSample Rate See(3) 200 ksps (max)
tCONV Conversion Time 13 SCLK cycles
30 % (min)
DC SCLK Duty Cycle fSCLK = 3.2 MHz 50 70 % (max)
tACQ Track/Hold Acquisition Time Full-Scale Step Input 3SCLK cycles
Throughput Time Acquisition Time + Conversion Time 16 SCLK cycles
(3) This is the frequency range over which the electrical performance is specified. The device is functional over a wider range which is
specified under Operating Ratings.
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ADC082S021 Timing Specifications
The following specifications apply for VA= +2.7V to 5.25V, GND = 0V, fSCLK = 0.8 MHz to 3.2 MHz, fSAMPLE = 50 ksps to 200
ksps, CL= 50 pF, Boldface limits apply for TA= TMIN to TMAX: all other limits TA= 25°C.
Parameter Test Conditions Typical Limits(1) Units
VA= +3.0V −3.5
tCSU Setup Time SCLK High to CS Falling Edge See(2) 10 ns (min)
VA= +5.0V −0.5
VA= +3.0V +4.5
tCLH Hold time SCLK Low to CS Falling Edge See(2) 10 ns (min)
VA= +5.0V +1.5
VA= +3.0V +4
tEN Delay from CS Until DOUT active 30 ns (max)
VA= +5.0V +2
VA= +3.0V +16.5
tACC Data Access Time after SCLK Falling Edge 30 ns (max)
VA= +5.0V +15
tSU Data Setup Time Prior to SCLK Rising Edge +3 10 ns (min)
tHData Valid SCLK Hold Time +3 10 ns (min)
tCH SCLK High Pulse Width 0.5 x tSCLK 0.3 x tSCLK ns (min)
tCL SCLK Low Pulse Width 0.5 x tSCLK 0.3 x tSCLK ns (min)
VA= +3.0V 1.7
Output Falling VA= +5.0V 1.2
tDIS CS Rising Edge to DOUT High-Impedance 20 ns (max)
VA= +3.0V 1.0
Output Rising VA= +5.0V 1.0
(1) Tested limits are ensured to TI's AOQL (Average Outgoing Quality Level).
(2) Clock may be either high or low when CS is asserted as long as setup and hold times tCSU and tCLH are strictly observed.
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tCSU
tCLH
SCLK
CS
SCLK
tCONVERT
tACQ
tCL tACC
tEN
Z3 Z2 Z1 Z0 DB6
DONT DONTC ADD2 ADD1 ADD0 DONTC DONTC DONTC
DB7 DB5 DB4 DB0
16
87654321
DIN
DOUT
SCLK
CS
tDIS
Zero ZeroDB1
151413
Tri-State
Zero Zero
1211
tCH
tH
tSU
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 1 2 3 4 5 6 7 8
Track Hold
Power Up
Track Hold
b7 b6 b5 b4 b3 b2 b1 b0 b7 b6 b5 b4 b3 b2 b1 b0
9 10
DB5 DB4 DB3 DB2 DB1 DB0 DB5 DB4 DB3
DIN
DOUT
Power Up
SCLK
CS
Power Down
Control register Control register
DB7 DB6 DB7 DB6
ADC082S021
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SNAS282D –APRIL 2005–REVISED MARCH 2013
Timing Diagrams
Figure 2. ADC082S021 Operational Timing Diagram
Figure 3. Timing Test Circuit
Figure 4. ADC082S021 Serial Timing Diagram
Figure 5. SCLK and CS Timing Parameters
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Specification Definitions
ACQUISITION TIME is the time required to acquire the input voltage. That is, it is time required for the hold
capacitor to charge up to the input voltage.
APERTURE DELAY is the time between the fourth falling SCLK edge of a conversion and the time when the
input signal is acquired or held for conversion.
CONVERSION TIME is the time required, after the input voltage is acquired, for the ADC to convert the input
voltage to a digital word.
CROSSTALK is the coupling of energy from one channel into the other channel, or the amount of signal energy
from one analog input that appears at the measured analog input.
DIFFERENTIAL NON-LINEARITY (DNL) is the measure of the maximum deviation from the ideal step size of 1
LSB.
DUTY CYCLE is the ratio of the time that a repetitive digital waveform is high to the total time of one period. The
specification here refers to the SCLK.
EFFECTIVE NUMBER OF BITS (ENOB, or EFFECTIVE BITS) is another method of specifying Signal-to-Noise
and Distortion or SINAD. ENOB is defined as (SINAD −1.76) / 6.02 and says that the converter is equivalent to
a perfect ADC of this (ENOB) number of bits.
FULL POWER BANDWIDTH is a measure of the frequency at which the reconstructed output fundamental
drops 3 dB below its low frequency value for a full scale input.
FULL SCALE ERROR (FSE) is a measure of how far the last code transition is from the ideal 1½ LSB below
VREF+and is defined as:
VFSE = Vmax + 1.5 LSB – VREF+
where
• Vmax is the voltage at which the transition to the maximum code occurs. FSE can be expressed in Volts, LSB
or percent of full scale range. (1)
GAIN ERROR is the deviation of the last code transition (111...110) to (111...111) from the ideal (VREF −1.5
LSB), after adjusting for offset error.
INTEGRAL NON-LINEARITY (INL) is a measure of the deviation of each individual code from a line drawn from
negative full scale (½ LSB below the first code transition) through positive full scale (½ LSB above the last code
transition). The deviation of any given code from this straight line is measured from the center of that code value.
INTERMODULATION DISTORTION (IMD) is the creation of additional spectral components that are present at
the output and are not present at the input and result from two sinusoidal frequencies being applied to the ADC
input at the same time. It is defined as the ratio of the power in the intermodulation products to the total power in
one of the original frequencies. IMD is usually expressed in dB.
MISSING CODES are those output codes that will never appear at the ADC outputs. These codes cannot be
reached with any input value. The ADC082S021 is specified not to have any missing codes.
OFFSET ERROR is the deviation of the first code transition (000...000) to (000...001) from the ideal (i.e. GND +
0.5 LSB).
SIGNAL TO NOISE RATIO (SNR) is the ratio, expressed in dB, of the rms value of the input signal at the
converter output to the rms value of the sum of all other spectral components below one-half the sampling
frequency, not including d.c. or harmonics included in the THD specification.
SIGNAL TO NOISE PLUS DISTORTION (S/(N+D) or SINAD or SNDR) is the ratio, expressed in dB, of the rms
value of the input signal at the output to the rms value of all of the other spectral components below half the
clock frequency, including all harmonics but excluding DC.
SPURIOUS FREE DYNAMIC RANGE (SFDR) is the difference, expressed in dB, between the rms values of the
input signal at the output and the peak spurious signal, where a spurious signal is any signal present in the
output spectrum that is not present at the input, excluding d.c.
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2
1f
2
6f
2
2f
10
‡AA++A
log20=THD
ADC082S021
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TOTAL HARMONIC DISTORTION (THD) is the ratio, expressed in dBc, of the rms total of the first five harmonic
components at the output to the rms level of the input signal frequency as seen at the output. THD is calculated
as
where
• Af1 is the RMS power of the input frequency at the output and Af2 through Af6 are the RMS power in the first 5
harmonic frequencies. Accurate THD measurement requires a spectrally pure sine wave (monotone) at the
ADC input. (2)
THROUGHPUT TIME is the minimum time required between the start of two successive conversion. It is the
acquisition time plus the conversion and read out times. In the case of the ADC082S021, this is 16 SCLK
periods.
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Typical Performance Characteristics
TA= +25°C, fSAMPLE = 50 ksps to 200 ksps, fSCLK = 0.8 MHz to 3.2 MHz, fIN = 39.9 kHz unless otherwise stated.
DNL - VA= 3.0V INL - VA= 3.0V
Figure 6. Figure 7.
DNL - VA= 5.0V INL - VA= 5.0V
Figure 8. Figure 9.
DNL vs. Supply INL vs. Supply
Figure 10. Figure 11.
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Typical Performance Characteristics (continued)
TA= +25°C, fSAMPLE = 50 ksps to 200 ksps, fSCLK = 0.8 MHz to 3.2 MHz, fIN = 39.9 kHz unless otherwise stated.
DNL vs. Clock Frequency INL vs. Clock Frequency
Figure 12. Figure 13.
DNL vs. Clock Duty Cycle INL vs. Clock Duty Cycle
Figure 14. Figure 15.
DNL vs. Temperature INL vs. Temperature
Figure 16. Figure 17.
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Typical Performance Characteristics (continued)
TA= +25°C, fSAMPLE = 50 ksps to 200 ksps, fSCLK = 0.8 MHz to 3.2 MHz, fIN = 39.9 kHz unless otherwise stated.
SNR vs. Supply THD vs. Supply
Figure 18. Figure 19.
SNR vs. Clock Frequency THD vs. Clock Frequency
Figure 20. Figure 21.
SNR vs. Clock Duty Cycle THD vs. Clock Duty Cycle
Figure 22. Figure 23.
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Typical Performance Characteristics (continued)
TA= +25°C, fSAMPLE = 50 ksps to 200 ksps, fSCLK = 0.8 MHz to 3.2 MHz, fIN = 39.9 kHz unless otherwise stated.
SNR vs. Input Frequency THD vs. Input Frequency
Figure 24. Figure 25.
SNR vs. Temperature THD vs. Temperature
Figure 26. Figure 27.
SFDR vs. Supply SINAD vs. Supply
Figure 28. Figure 29.
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Typical Performance Characteristics (continued)
TA= +25°C, fSAMPLE = 50 ksps to 200 ksps, fSCLK = 0.8 MHz to 3.2 MHz, fIN = 39.9 kHz unless otherwise stated.
SFDR vs. Clock Frequency SINAD vs. Clock Frequency
Figure 30. Figure 31.
SFDR vs. Clock Duty Cycle SINAD vs. Clock Duty Cycle
Figure 32. Figure 33.
SFDR vs. Input Frequency SINAD vs. Input Frequency
Figure 34. Figure 35.
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Typical Performance Characteristics (continued)
TA= +25°C, fSAMPLE = 50 ksps to 200 ksps, fSCLK = 0.8 MHz to 3.2 MHz, fIN = 39.9 kHz unless otherwise stated.
SFDR vs. Temperature SINAD vs. Temperature
Figure 36. Figure 37.
ENOB vs. Supply ENOB vs. Clock Frequency
Figure 38. Figure 39.
ENOB vs. Clock Duty Cycle ENOB vs. Input Frequency
Figure 40. Figure 41.
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Typical Performance Characteristics (continued)
TA= +25°C, fSAMPLE = 50 ksps to 200 ksps, fSCLK = 0.8 MHz to 3.2 MHz, fIN = 39.9 kHz unless otherwise stated.
ENOB vs. Temperature Spectral Response - 3V, 200 ksps
Figure 42. Figure 43.
Spectral Response - 5V, 200 ksps Power Consumption vs. Throughput
Figure 44. Figure 45.
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IN1 MUX
GND
SAMPLING
CAPACITOR
SW1
-
+CONTROL
LOGIC
CHARGE
REDISTRIBUTION
DAC
SW2
IN2
VA
2
IN1 MUX
GND
SAMPLING
CAPACITOR
SW1
-
+CONTROL
LOGIC
CHARGE
REDISTRIBUTION
DAC
SW2
IN2
VA
2
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APPLICATIONS INFORMATION
ADC082S021 OPERATION
The ADC082S021 is a successive-approximation analog-to-digital converter designed around a charge-
redistribution digital-to-analog converter. Simplified schematics of the ADC082S021 in both track and hold modes
are shown in Figure 46 and Figure 47, respectively. In Figure 46, the ADC082S021 is in track mode: switch SW1
connects the sampling capacitor to one of two analog input channels through the multiplexer, and SW2 balances
the comparator inputs. The ADC082S021 is in this state for the first three SCLK cycles after CS is brought low.
Figure 47 shows the ADC082S021 in hold mode: switch SW1 connects the sampling capacitor to ground,
maintaining the sampled voltage, and switch SW2 unbalances the comparator. The control logic then instructs
the charge-redistribution DAC to add fixed amounts of charge to the sampling capacitor until the comparator is
balanced. When the comparator is balanced, the digital word supplied to the DAC is the digital representation of
the analog input voltage. The ADC082S021 is in this state for the fourth through sixteenth SCLK cycles after CS
is brought low.
The time when CS is low is considered a serial frame. Each of these frames should contain an integer multiple of
16 SCLK cycles, during which time a conversion is performed and the result is clocked out at the DOUT pin while
the multiplexer address for the next conversion is clocked in at the DIN pin.
Figure 46. ADC082S021 in Track Mode
Figure 47. ADC082S021 in Hold Mode
USING THE ADC082S021
An ADC082S021 timing diagram and a serial interface timing diagram for the ADC082S021 are shown in the
Timing Diagrams section. CS is chip select, which initiates conversions and frames the serial data transfers.
SCLK (serial clock) controls both the conversion process and the timing of serial data. DOUT is the serial data
output pin, where the conversion result is sent out as a serial data stream, MSB first. Data to be written to the
ADC082S021's Control Register is placed at DIN, the serial data input pin. New data is written in at DIN with
each conversion.
A serial frame is initiated on the falling edge of CS and ends on the rising edge of CS. Each frame must contain
an integer multiple of 16 rising SCLK edges. The ADC output data (DOUT) is in a high impedance state when
CS is high and is active when CS is low. Thus, CS acts as an output enable. Additionally, the device goes into a
power down state when CS is high and also between continuous conversion cycles.
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ADC082S021
SNAS282D –APRIL 2005–REVISED MARCH 2013
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During the first 3 cycles of SCLK, the ADC is in the track mode acquiring the input voltage. For the next 13 SCLK
cycles, the conversion is accomplished and the data is clocked out, MSB first, starting with the 5th clock. If there
is more than one conversion in a frame, the ADC will re-enter the track mode on the falling edge of SCLK after
the N*16th rising edge of SCLK, and re-enter the hold/convert mode on the N*16+4th falling edge of SCLK,
where "N" is an integer.
When CS is brought high, SCLK is internally gated off. If SCLK is stopped in the low state while CS is high, the
subsequent fall of CS will generate a falling edge of the internal version of SCLK, putting the ADC into the track
mode. This is seen by the ADC as the first falling edge of SCLK. If SCLK is stopped with SCLK high, the ADC
enters the track mode on the first falling edge of SCLK after the falling edge of CS.
During each conversion, data is clocked into the ADC at DIN on the first 8 rising edges of SCLK after the fall of
CS. For each conversion, it is necessary to clock in the data indicating the input that is selected for the
conversion after the current one. See Table 2,Table 3, and Table 4.
If CS and SCLK go low within the times defined by tCSU and tCLH, the rising edge of SCLK that begins clocking
data in at DIN may or may not be one clock cycle later than expected. It is, therefore, best to strictly observe the
minimum tCSU and tCLH times given in the Timing Specifications.
There are no power-up delays or dummy conversions required with the ADC082S021. The ADC is able to
sample and convert an input to full conversion immediately following power up. The first conversion result after
power-up will be that of IN1.
Table 2. Control Register Bits
Bit 7 (MSB) Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
DONTC DONTC ADD2 ADD1 ADD0 DONTC DONTC DONTC
Table 3. Control Register Bit Descriptions
Bit #: Symbol: Description
7 - 6, 2 - 0 DONTC Don't care. The value of these bits do not affect the device.
3 ADD0 These bits determine which input channel will be sampled and converted in the next track/hold
cycle. The mapping between codes and channels is shown in Table 4.
4 ADD1
5 ADD2
Table 4. Input Channel Selection
ADD2 ADD1 ADD0 Input Channel
x 0 0 IN1 (Default)
x 0 1 IN2
x 1 x Not allowed. The output signal at the DOUT pin is indeterminate if ADD1 is high.
18 Submit Documentation Feedback Copyright © 2005–2013, Texas Instruments Incorporated
Product Folder Links: ADC082S021
IN1
IN2
MICROPROCESSOR
DSP
SCLK
CS
DIN
DOUT
GND
VA
ADC082S021
LP2950 5V
1 PF0.1 PF 0.1 PF1 PF
ADC082S021
www.ti.com
SNAS282D –APRIL 2005–REVISED MARCH 2013
ADC082S021 TRANSFER FUNCTION
The output format of the ADC082S021 is straight binary. Code transitions occur midway between successive
integer LSB values. The LSB width for the ADC082S021 is VA/256. The ideal transfer characteristic is shown in
Figure 48. The transition from an output code of 0000 0000 to a code of 0000 0001 is at 1/2 LSB, or a voltage of
VA/512. Other code transitions occur at steps of one LSB.
Figure 48. Ideal Transfer Characteristic
TYPICAL APPLICATION CIRCUIT
A typical application of the ADC082S021 is shown in Figure 49. Power is provided, in this example, by the Texas
Instruments LP2950 low-dropout voltage regulator, available in a variety of fixed and adjustable output voltages.
The power supply pin is bypassed with a capacitor network located close to the ADC082S021. Because the
reference for the ADC082S021 is the supply voltage, any noise on the supply will degrade device noise
performance. To keep noise off the supply, use a dedicated linear regulator for this device, or provide sufficient
decoupling from other circuitry to prevent noise from reaching the ADC082S021 supply pin. Because of the
ADC082S021's low power requirements, it is also possible to use a precision reference as a power supply to
maximize performance. The four-wire interface is shown connected to a microprocessor or DSP.
Figure 49. Typical Application Circuit
Copyright © 2005–2013, Texas Instruments Incorporated Submit Documentation Feedback 19
Product Folder Links: ADC082S021
VIN
D1 R1
500 C2
30 pF
VA
D2
C1
3 pF
Conversion Phase - Switch Open
Track Phase - Switch Closed
ADC082S021
SNAS282D –APRIL 2005–REVISED MARCH 2013
www.ti.com
ANALOG INPUTS
An equivalent circuit for one of the ADC082S021's input channels is shown in Figure 50. Diodes D1 and D2
provide ESD protection for the analog inputs. At no time should any input go beyond (VA+ 300 mV) or (GND −
300 mV), as these ESD diodes will begin conducting, which could result in erratic operation. For this reason,
these ESD diodes should NOT be used to clamp the input signal.
The capacitor C1 in Figure 50 has a typical value of 3 pF, and is mainly the package pin capacitance. Resistor
R1 is the on resistance of the multiplexer and track / hold switch, and is typically 500 ohms. Capacitor C2 is the
ADC082S021 sampling capacitor and is typically 30 pF. The ADC082S021 will deliver best performance when
driven by a low-impedance source to eliminate distortion caused by the charging of the sampling capacitance.
This is especially important when using the ADC082S021 to sample AC signals. Also important when sampling
dynamic signals is a band-pass or low-pass filter to reduce harmonics and noise, improving dynamic
performance.
Figure 50. Equivalent Input Circuit
DIGITAL INPUTS AND OUTPUTS
The ADC082S021's digital output DOUT is limited by, and cannot exceed, the supply voltage, VA. The digital
input pins are not prone to latch-up and, and although not recommended, SCLK, CS and DIN may be asserted
before VAwithout latchup risk.
POWER SUPPLY CONSIDERATIONS
The ADC082S021 is fully powered-up whenever CS is low, and fully powered-down whenever CS is high, with
one exception: the ADC082S021 automatically enters power-down mode between the 16th falling edge of a
conversion and the 1st falling edge of the subsequent conversion (see Timing Diagrams).
The ADC082S021 can perform multiple conversions back to back; each conversion requires 16 SCLK cycles.
The ADC082S021 will perform conversions continuously as long as CS is held low.
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ADC082S021
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SNAS282D –APRIL 2005–REVISED MARCH 2013
Power Management
When the ADC082S021 is operated continuously in normal mode, the maximum throughput is fSCLK/16.
Throughput may be traded for power consumption by running fSCLK at its maximum 3.2 MHz and performing
fewer conversions per unit time, putting the ADC082S021 into shutdown mode between conversions. A plot of
typical power consumption versus throughput is shown in the Typical Performance Characteristics section. To
calculate the power consumption for a given throughput, multiply the fraction of time spent in the normal mode by
the normal mode power consumption and add the fraction of time spent in shutdown mode multiplied by the
shutdown mode power consumption. Generally, the user will put the part into normal mode and then put the part
back into shutdown mode. Note that the curve of power consumption vs. throughput is nearly linear. This is
because the power consumption in the shutdown mode is so small that it can be ignored for all practical
purposes.
Power Supply Noise Considerations
The charging of any output load capacitance requires current from the power supply, VA. The current pulses
required from the supply to charge the output capacitance will cause voltage variations on the supply. If these
variations are large enough, they could degrade SNR and SINAD performance of the ADC. Furthermore,
discharging the output capacitance when the digital output goes from a logic high to a logic low will dump current
into the die substrate, which is resistive. Load discharge currents will cause "ground bounce" noise in the
substrate that will degrade noise performance if that current is large enough. The larger is the output
capacitance, the more current flows through the die substrate and the greater is the noise coupled into the
analog channel, degrading noise performance.
To keep noise out of the power supply, keep the output load capacitance as small as practical. If the load
capacitance is greater than 50 pF, use a 100 Ωseries resistor at the ADC output, located as close to the ADC
output pin as practical. This will limit the charge and discharge current of the output capacitance and improve
noise performance.
Copyright © 2005–2013, Texas Instruments Incorporated Submit Documentation Feedback 21
Product Folder Links: ADC082S021
ADC082S021
SNAS282D –APRIL 2005–REVISED MARCH 2013
www.ti.com
REVISION HISTORY
Changes from Revision C (March 2013) to Revision D Page
• Changed layout of National Data Sheet to TI format .......................................................................................................... 21
22 Submit Documentation Feedback Copyright © 2005–2013, Texas Instruments Incorporated
Product Folder Links: ADC082S021
PACKAGE OPTION ADDENDUM
www.ti.com 10-Dec-2020
Addendum-Page 1
PACKAGING INFORMATION
Orderable Device Status
(1)
Package Type Package
Drawing Pins Package
Qty Eco Plan
(2)
Lead finish/
Ball material
(6)
MSL Peak Temp
(3)
Op Temp (°C) Device Marking
(4/5)
Samples
ADC082S021CIMM/NOPB ACTIVE VSSOP DGK 8 1000 RoHS & Green SN Level-1-260C-UNLIM -40 to 85 X16C
ADC082S021CIMMX/NOPB ACTIVE VSSOP DGK 8 3500 RoHS & Green SN Level-1-260C-UNLIM -40 to 85 X16C
(1) The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2) RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance
do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may
reference these types of products as "Pb-Free".
RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption.
Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of <=1000ppm threshold. Antimony trioxide based
flame retardants must also meet the <=1000ppm threshold requirement.
(3) MSL, Peak Temp. - The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.
(4) There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device.
(5) Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation
of the previous line and the two combined represent the entire Device Marking for that device.
(6) Lead finish/Ball material - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead finish/Ball material values may wrap to two
lines if the finish value exceeds the maximum column width.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information
provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and
continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals.
TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release.
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.
PACKAGE OPTION ADDENDUM
www.ti.com 10-Dec-2020
Addendum-Page 2
TAPE AND REEL INFORMATION
*All dimensions are nominal
Device Package
Type Package
Drawing Pins SPQ Reel
Diameter
(mm)
Reel
Width
W1 (mm)
A0
(mm) B0
(mm) K0
(mm) P1
(mm) W
(mm) Pin1
Quadrant
ADC082S021CIMM/NOPB VSSOP DGK 8 1000 178.0 12.4 5.3 3.4 1.4 8.0 12.0 Q1
ADC082S021CIMMX/NOP
BVSSOP DGK 8 3500 330.0 12.4 5.3 3.4 1.4 8.0 12.0 Q1
PACKAGE MATERIALS INFORMATION
www.ti.com 23-Sep-2013
Pack Materials-Page 1
*All dimensions are nominal
Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm)
ADC082S021CIMM/NOPB VSSOP DGK 8 1000 210.0 185.0 35.0
ADC082S021CIMMX/NOP
BVSSOP DGK 8 3500 367.0 367.0 35.0
PACKAGE MATERIALS INFORMATION
www.ti.com 23-Sep-2013
Pack Materials-Page 2
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