ADC081S101
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SNAS310D – JANUARY 2006 – REVISED JANUARY 2014
ADC081S101 Single Channel, 0.5 to 1 Msps, 8-Bit A/D Converter
Check for Samples: ADC081S101
FEATURES
DESCRIPTION
•
•
•
•
•
The ADC081S101 is a low-power, single channel
CMOS 8-bit analog-to-digital converter with a highspeed serial interface. Unlike the conventional
practice of specifying performance at a single sample
rate only, the ADC081S101 is fully specified over a
sample rate range of 500 ksps to 1 Msps. The
converter is based upon a successive-approximation
register architecture with an internal track-and-hold
circuit.
1
2
Specified Over a Range of Sample Rates.
6-Lead WSON and SOT-23 Packages
Variable Power Management
Single Power Supply with 2.7V - 5.25V Range
SPI™/QSPI™/MICROWIRE/DSP Compatible
APPLICATIONS
•
•
•
Portable Systems
Remote Data Aquisitions
Instrumentation and Control Systems
The output serial data is straight binary, and is
compatible with several standards, such as SPI™,
QSPI™, MICROWIRE, and many common DSP
serial interfaces.
KEY SPECIFICATIONS
•
•
•
•
The ADC081S101 operates with a single supply that
can range from +2.7V to +5.25V. Normal power
consumption using a +3V or +5V supply is 2.0 mW
and 10.0 mW, respectively. The power-down feature
reduces the power consumption to just 2.5 µW using
a +5V supply.
DNL ± 0.07 LSB (typ)
INL ± 0.05 LSB (typ)
SNR 49.7 dB (typ)
Power Consumption
– 3V Supply 2.0 mW (typ)
– 5V Supply 10.0 mW (typ)
The ADC081S101 is packaged in an 6-lead WSON
and SOT-23 packages. Operation over the industrial
temperature range of −40°C to +85°C is ensured.
Table 1. Pin-Compatible Alternatives by Resolution and Speed (1)
Resolution
(1)
Specified for Sample Rate Range of:
50 to 200 ksps
200 to 500 ksps
500 ksps to 1 Msps
12-bit
ADC121S021
ADC121S051
ADC121S101
10-bit
ADC101S021
ADC101S051
ADC101S101
8-bit
ADC081S021
ADC081S051
ADC081S101
All devices are fully pin and function compatible.
Connection Diagram
VA
1
GND
2
VIN
3
ADC081S101
6
CS
5
SDATA
4
SCLK
Figure 1. 6-Lead SOT-23 or WSON
See DBV or NGF Package
1
2
Please 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.
All trademarks are the property of their respective owners.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2006–2014, Texas Instruments Incorporated
ADC081S101
SNAS310D – JANUARY 2006 – REVISED JANUARY 2014
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Block Diagram
VIN
T/H
8-BIT
SUCCESSIVE
APPROXIMATION
ADC
SCLK
CONTROL
LOGIC
CS
SDATA
PIN DESCRIPTIONS AND EQUIVALENT CIRCUITS
Pin No.
Symbol
Description
ANALOG I/O
3
VIN
Analog input. This signal can range from 0V to VA.
DIGITAL I/O
4
SCLK
Digital clock input. This clock directly controls the conversion and readout processes.
5
SDATA
6
CS
Chip select. On the falling edge of CS, a conversion process begins.
1
VA
Positive supply pin. This pin should be connected to a quiet +2.7V to +5.25V source and bypassed to
GND with a 1 µF capacitor and a 0.1 µF monolithic capacitor located within 1 cm of the power pin.
2
GND
The ground return for the supply and signals.
PAD
GND
For package suffix CISD(X) only, it is recommended that the center pad should be connected to ground.
Digital data output. The output samples are clocked out of this pin on falling edges of the SCLK pin.
POWER SUPPLY
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.
2
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Absolute Maximum Ratings
(1) (2) (3)
−0.3V to 6.5V
Analog Supply Voltage VA
Voltage on Any Pin to GND
−0.3V to (VA +0.3)V
(4)
±10 mA
Input Current at Any Pin
Package Input Current
(4)
±20 mA
Power Consumption at TA = 25°C
See
(5)
(6)
ESD Susceptibility
Human Body Model
Machine Model
3500V
300V
Junction Temperature
+150°C
Storage Temperature
−65°C to +150°C
(1)
(2)
(3)
(4)
(5)
(6)
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.
If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/ Distributors for availability and
specifications.
All voltages are measured with respect to GND = 0V, unless otherwise specified.
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 VA pin. The current into the VA pin is
limited by the Analog Supply Voltage specification.
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.
Human body model is 100 pF capacitor discharged through a 1.5 kΩ resistor. Machine model is 220 pF discharged through zero ohms.
Operating Ratings
(1) (2)
−40°C ≤ TA ≤ +85°C
Operating Temperature Range
VA Supply Voltage
+2.7V to +5.25V
Digital Input Pins Voltage Range
(regardless of supply voltage)
−0.3V to +5.25V
Clock Frequency
25 kHz to 20 MHz
Sample Rate
Up to 1 Msps
Analog Input Voltage
(1)
(2)
0V to VA
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.
All voltages are measured with respect to GND = 0V, unless otherwise specified.
Package Thermal Resistance (1)
θJA
Package
6-lead WSON
94°C / W
6-lead SOT-23
265°C / W
Soldering process must comply with Texas Instrument's Reflow Temperature Profile specifications. Refer to www.ti.com and
http://www.ti.com/lit/SNOA549.
(1)
Reflow temperature profiles are different for lead-free and non-lead-free packages.
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ADC081S101 Converter Electrical Characteristics
(1) (2)
The following specifications apply for VA = +2.7V to 5.25V, GND = 0V, fSCLK = 10 MHz to 20 MHz, CL = 15 pF, fSAMPLE = 500
ksps to 1 Msps, unless otherwise noted. Boldface limits apply for TA = TMIN to TMAX: all other limits TA = 25°C.
Symbol
Parameter
Conditions
Typical
Limits
(2)
Units
8
Bits
STATIC CONVERTER CHARACTERISTICS
Resolution with No Missing
Codes
INL
Integral Non-Linearity
VA = +2.7V to +5.25V
±0.05
±0.3
LSB
(max)
DNL
Differential Non-Linearity
VA = +2.7V to +5.25V
±0.07
±0.3
LSB
(max)
VOFF
Offset Error
VA = +2.7V to +5.25V
±0.03
±0.3
LSB
(max)
GE
Gain Error
VA = +2.7V to +5.25V
±0.08
±0.4
LSB
(max)
TUE
Total Unadjusted Error
VA = +2.7V to +5.25V
±0.07
±0.3
LSB
(max)
49
dB (min)
DYNAMIC CONVERTER CHARACTERISTICS
SINAD
Signal-to-Noise Plus
Distortion Ratio
VA = +2.7 to 5.25V
fIN = 100 kHz, −0.02 dBFS
49.7
SNR
Signal-to-Noise Ratio
VA = +2.7 to 5.25V
fIN = 100 kHz, −0.02 dBFS
49.7
THD
Total Harmonic Distortion
VA = +2.7 to 5.25V
fIN = 100 kHz, −0.02 dBFS
−77
−65
dB (max)
SFDR
Spurious-Free Dynamic
Range
VA = +2.7 to 5.25V
fIN = 100 kHz, −0.02 dBFS
68
65
dB (min)
ENOB
Effective Number of Bits
VA = +2.7 to 5.25V
fIN = 100 kHz, −0.02 dBFS
7.9
7.8
Bits (min)
Intermodulation Distortion,
Second Order Terms
VA = +5.25V
fa = 103.5 kHz, fb = 113.5 kHz
−68
dB
Intermodulation Distortion,
Third Order Terms
VA = +5.25V
fa = 103.5 kHz, fb = 113.5 kHz
−68
dB
VA = +5V
11
MHz
VA = +3V
8
MHz
IMD
FPBW
-3 dB Full Power Bandwidth
dB (min)
ANALOG INPUT CHARACTERISTICS
VIN
Input Range
IDCL
DC Leakage Current
CINA
Input Capacitance
0 to VA
V
±1
µA (max)
Track Mode
30
pF
Hold Mode
4
pF
DIGITAL INPUT CHARACTERISTICS
VIH
Input High Voltage
VIL
Input Low Voltage
IIN
Input Current
CIND
Digital Input Capacitance
VA = +5.25V
2.4
VA = +3.6V
2.1
VA = +5V
0.8
VA = +3V
V (min)
V (max)
0.4
V (max)
±10 nA
±1
µA (max)
2
4
pF (max)
ISOURCE = 200 µA
VA − 0.07
VA − 0.2
V (min)
ISOURCE = 1 mA
VA − 0.1
ISINK = 200 µA
0.03
0.4
V (max)
ISINK = 1 mA
0.1
VIN = 0V or VA
DIGITAL OUTPUT CHARACTERISTICS
VOH
VOL
(1)
(2)
4
Output High Voltage
Output Low Voltage
V
V
Tested limits are specified to TI's AOQL (Average Outgoing Quality Level).
Data sheet min/max specification limits are ensured by design, test, or statistical analysis.
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ADC081S101 Converter Electrical Characteristics
(1)(2)
(continued)
The following specifications apply for VA = +2.7V to 5.25V, GND = 0V, fSCLK = 10 MHz to 20 MHz, CL = 15 pF, fSAMPLE = 500
ksps to 1 Msps, unless otherwise noted. Boldface limits apply for TA = TMIN to TMAX: all other limits TA = 25°C.
Symbol
Parameter
IOZL, IOZH
TRI-STATE® Leakage
Current
COUT
TRI-STATE® Output
Capacitance
Conditions
Typical
Output Coding
Limits
(2)
Units
±0.1
±10
µA (max)
2
4
pF (max)
Straight (Natural) Binary
POWER SUPPLY CHARACTERISTICS
VA
Supply Voltage
VA = +5.25V, fSAMPLE = 1 Msps
Supply Current, Normal
Mode (Operational, CS low)
VA = +3.6V, fSAMPLE = 1 Msps
IA
Supply Current, Shutdown
(CS high)
Power Consumption,
Normal Mode (Operational,
CS low)
WSON
SOT-23
WSON
2.0
0.6
V (min)
5.25
V (max)
3.2
mA
(max)
2.6
1.5
1.1
mA
(max)
VA = +5.25V, fSCLK = 0 MHz, fSAMPLE = 0 ksps
500
nA
VA = +5.25V, fSCLK = 20 MHz,
fSAMPLE = 0 ksps
60
µA
VA = +5V
VA = +3V
PD
Power Consumption,
Shutdown (CS high)
SOT-23
2.7
SOT-23
WSON
SOT-23
WSON
10
2.0
16
13
4.5
3.3
mW
(max)
mW
(max)
VA = +5V, fSCLK = 0 MHz,
fSAMPLE = 0 ksps
2.5
µW
VA = +5V, fSCLK = 20 MHz,
fSAMPLE = 0 ksps
300
µW
AC ELECTRICAL CHARACTERISTICS
fSCLK
Clock Frequency
Sample Rate
tHOLD
Hold Time
DC
SCLK Duty Cycle
tACQ
Minimum Time Required for
Acquisition
tQUIET
MHz
(min)
20
MHz
(max)
500
ksps
(min)
1
Msps
(max)
13
SCLk
Falling
Edges
40
% (min)
60
% (max)
350
ns (max)
50
ns (min)
(3)
50
fS
10
(3)
fSCLK = 20 MHz
50
(4)
tAD
Aperture Delay
3
ns
tAJ
Aperture Jitter
30
ps
(3)
(4)
This is the frequency range over which the electrical performance is ensured. The device is functional over a wider range which is
specified under Operating Ratings.
Minimum Quiet Time required by bus relinquish and the start of the next conversion.
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ADC081S101 Timing Specifications
The following specifications apply for VA = +2.7V to 5.25V, GND = 0V, fSCLK = 10.0 MHz to 20.0 MHz, CL = 25 pF, fSAMPLE =
500 ksps to 1 Msps, Boldface limits apply for TA = TMIN to TMAX: all other limits TA = 25°C.
Symbol
Parameter
Conditions
tCS
Minimum CS Pulse Width
tSU
CS to SCLK Setup Time
tEN
Delay from CS Until SDATA TRI-STATE Disabled
tACC
Data Access Time after SCLK Falling Edge
(2)
Typical
Limits
Units
10
ns (min)
10
ns (min)
20
ns (max)
VA = +2.7 to +3.6
40
ns (max)
VA = +4.75 to +5.25
20
ns (max)
(1)
tCL
SCLK Low Pulse Width
0.4 x tSCLK
ns (min)
tCH
SCLK High Pulse Width
0.4 x tSCLK
ns (min)
7
ns (min)
tH
VA = +2.7 to +3.6
SCLK to Data Valid Hold Time
VA = +4.75 to +5.25
VA = +2.7 to +3.6
tDIS
SCLK Falling Edge to SDATA High Impedance
(3)
VA = +4.75 to +5.25
tPOWER-
Power-Up Time from Full Power-Down
1
5
ns (min)
25
ns (max)
6
ns (min)
25
ns (max)
5
ns (min)
µs
UP
(1)
(2)
(3)
Measured with the timing test circuit shown in Figure 2 and defined as the time taken by the output signal to cross 1.0V.
Measured with the timing test circuit shown in Figure 2 and defined as the time taken by the output signal to cross 1.0V or 2.0V.
tDIS is derived from the time taken by the outputs to change by 0.5V with the timing test circuit shown in Figure 2. The measured number
is then adjusted to remove the effects of charging or discharging the output capacitance. This means that tDIS is the true bus relinquish
time, independent of the bus loading.
Timing Diagrams
IOL
200 PA
1.6 V
To Output Pin
CL
25 pF
IOH
200 PA
Figure 2. Timing Test Circuit
6
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Track
Hold
|
CS
tCS
tSU
tACQ
tCL
1
2
3
|
SCLK
4
5
14
15
16
Z1
Z0
DB7
3 leading zero bits
17
18
19
20
tQUIET
tCH
|
Z2
13
tACC
tEN
SDATA
12
tH
tDIS
TRI-STATE
Zero
Zero
8 data bits
Zero
Zero
4 trailing zeroes
Figure 3. ADC081S101 Serial Timing Diagram
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. Acquisition time is measured backwards from the falling edge
of CS when the signal is sampled and the part moves from track to hold. The start of the time interval that
contains TACQ is the 13th rising edge of SCLK of the previous conversion when the part moves from hold
to track. The user must ensure that the time between the 13th rising edge of SCLK and the falling edge of
the next CS is not less than TACQ to meet performance specifications.
APERTURE DELAY is the time after the falling edge of CS when the input signal is acquired or held for
conversion.
APERTURE JITTER (APERTURE UNCERTAINTY) is the variation in aperture delay from sample to sample.
Aperture jitter manifests itself as noise in the output.
CONVERSION TIME is the time required, after the input voltage is acquired, for the ADC to convert the input
voltage to a digital word. This is from the falling edge of CS when the input signal is sampled to the 16th
falling edge of SCLK when the SDATA output goes into TRI-STATE.
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.
GAIN ERROR is the deviation of the last code transition (111...110) to (111...111) from the ideal (VREF − 1 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 as a result of two
sinusoidal frequencies being applied to the ADC input at the same time. It is defined as the ratio of the
power in the second and third order intermodulation products to the sum of the power in both of the
original frequencies. IMD is usually expressed in dB.
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MISSING CODES are those output codes that will never appear at the ADC outputs. The ADC081S101 is
ensured 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 +
1 LSB).
SIGNAL TO NOISE RATIO (SNR) is the ratio, expressed in dB, of the rms value of the input signal to the rms
value of the sum of all other spectral components below one-half the sampling frequency, not including
harmonics or d.c.
SIGNAL TO NOISE PLUS DISTORTION (S/N+D or SINAD) Is the ratio, expressed in dB, of the rms value of
the input signal to the rms value of all of the other spectral components below half the clock frequency,
including harmonics but excluding d.c.
SPURIOUS FREE DYNAMIC RANGE (SFDR) is the difference, expressed in dB, between the desired signal
amplitude to the amplitude of the peak spurious spectral component, where a spurious spectral
component is any signal present in the output spectrum that is not present at the input and may or may
not be a harmonic.
TOTAL HARMONIC DISTORTION (THD) is the ratio, expressed in dB or 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
THD = 20 ‡ log10
A f 22 + + A f 6 2
A f 12
where
•
•
Af1 is the RMS power of the input frequency at the output
Af2 through Af6 are the RMS power in the first 5 harmonic frequencies
(1)
TOTAL UNADJUSTED ERROR is the worst deviation found from the ideal transfer function. As such, it is a
comprehensive specification which includes full scale error, linearity error, and offset error.
THROUGHPUT TIME is the minimum time required between the start of two successive conversion. It is the
acquisition time plus the conversion time.
8
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Typical Performance Characteristics
TA = +25°C, fSAMPLE = 500 ksps to 1 Msps, fSCLK = 10 MHz to 20 MHz, fIN = 100 kHz unless otherwise stated.
DNL
fSCLK = 10 MHz
INL
fSCLK = 10 MHz
Figure 4.
Figure 5.
DNL
fSCLK = 20 MHz
INL
fSCLK = 20 MHz
Figure 6.
Figure 7.
DNL
vs
Clock Frequency
INL
vs
Clock Frequency
Figure 8.
Figure 9.
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Typical Performance Characteristics (continued)
TA = +25°C, fSAMPLE = 500 ksps to 1 Msps, fSCLK = 10 MHz to 20 MHz, fIN = 100 kHz unless otherwise stated.
10
Total Unadjusted Error
vs
Clock Frequency
SNR
vs
Clock Frequency
Figure 10.
Figure 11.
SINAD
vs.
Clock Frequency
THD
vs.
Clock Frequency
Figure 12.
Figure 13.
SFDR
vs.
Clock Frequency
Spectral Response, VA = 5V
fSCLK = 10 MHz
Figure 14.
Figure 15.
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Typical Performance Characteristics (continued)
TA = +25°C, fSAMPLE = 500 ksps to 1 Msps, fSCLK = 10 MHz to 20 MHz, fIN = 100 kHz unless otherwise stated.
Spectral Response, VA = 5V
fSCLK = 20 MHz
Power Consumption
vs.
Throughput,
fSCLK = 20 MHz
Figure 16.
Figure 17.
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APPLICATIONS INFORMATION
ADC081S101 Operation
The ADC081S101 is a successive-approximation analog-to-digital converter designed around a chargeredistribution digital-to-analog converter core. Simplified schematics of the ADC081S101 in both track and hold
operation are shown in Figure 18 and Figure 19, respectively. In Figure 18, the device is in track mode: switch
SW1 connects the sampling capacitor to the input, and SW2 balances the comparator inputs. The device is in
this state until CS is brought low, at which point the device moves to hold mode.
Figure 19 shows the device 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 chargeredistribution DAC to add or subtract fixed amounts of charge from 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 device moves from hold mode to track mode on the 13th rising edge of SCLK.
CHARGE
REDISTRIBUTION
DAC
VIN
SAMPLING
CAPACITOR
SW1
+
SW2
GND
CONTROL
LOGIC
-
VA
2
Figure 18. ADC081S101 in Track Mode
CHARGE
REDISTRIBUTION
DAC
VIN
SAMPLING
CAPACITOR
SW1
+
SW2
GND
-
CONTROL
LOGIC
VA
2
Figure 19. ADC081S101 in Hold Mode
Using the ADC081S101
The serial interface timing diagram for the ADC is shown in Figure 3. CS is chip select, which initiates
conversions on the ADC and frames the serial data transfers. SCLK (serial clock) controls both the conversion
process and the timing of serial data. SDATA is the serial data out pin, where a conversion result is found as a
serial data stream.
Basic operation of the ADC begins with CS going low, which initiates a conversion process and data transfer.
Subsequent rising and falling edges of SCLK will be labelled with reference to the falling edge of CS; for
example, "the third falling edge of SCLK" shall refer to the third falling edge of SCLK after CS goes low.
At the fall of CS, the SDATA pin comes out of TRI-STATE, and the converter moves from track mode to hold
mode. The input signal is sampled and held for conversion on the falling edge of CS. The converter moves from
hold mode to track mode on the 13th rising edge of SCLK (see Figure 3). It is at this point that the interval for the
TACQ specification begins. At least 350ns must pass between the 13th rising edge of SCLK and the next falling
edge of CS. The SDATA pin will be placed back into TRI-STATE after the 16th falling edge of SCLK, or at the
rising edge of CS, whichever occurs first. After a conversion is completed, the quiet time tQUIET must be satisfied
before bringing CS low again to begin another conversion.
12
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Sixteen SCLK cycles are required to read a complete sample from the ADC. The sample bits (including leading
or trailing zeroes) are clocked out on falling edges of SCLK, and are intended to be clocked in by a receiver on
subsequent falling edges of SCLK. The ADC will produce three leading zero bits on SDATA, followed by eight
data bits, most significant first. After the data bits, the ADC will clock out four trailing zeros.
If CS goes low before the rising edge of SCLK, an additional (fourth) zero bit may be captured by the next falling
edge of SCLK.
Determining Throughput
Throughput depends on the frequency of SCLK and how much time is allowed to elapse between the end of one
conversion and the start of another. At the maximum specified SCLK frequency, the maximum ensured
throughput is obtained by using a 20 SCLK frame. As shown in Figure 3, the minimum allowed time between CS
falling edges is determined by 1) 12.5 SCLKs for Hold mode, 2) the larger of two quantities: either the minimum
required time for Track mode (tACQ) or 2.5 SCLKs to finish reading the result and 3) 0, 1/2 or 1 SCLK padding to
ensure an even number of SCLK cycles so there is a falling SCLK edge when CS next falls. For example, at the
fastest rate for this family of parts, SCLK is 20MHz and 2.5 SCLKs are 125ns, so the minimum time between CS
falling edges is calculated by:
12.5*50ns + 350ns + 0.5*50ns = 1000ns
(2)
(12.5 SCLKs + tACQ + 1/2 SCLK) which corresponds to a maximum throughput of 1MSPS. At the slowest rate for
this family, SCLK is 1MHz. Using a 20-cycle conversion frame as shown in Figure 3 yields a 20μs time between
CS falling edges for a throughput of 50KSPS.
It is possible, however, to use fewer than 20 clock cycles provided the timing parameters are met. With a 1MHz
SCLK, there are 2500ns in 2.5 SCLK cycles, which is greater than tACQ. After the last data bit has come out, the
clock will need one full cycle to return to a falling edge. Thus the total time between falling edges of CS is
12.5*1μs +2.5*1μs +1*1μs=16μs which is a throughput of 62.5KSPS.
ADC081S101 Transfer Function
The output format of the ADC is straight binary. Code transitions occur midway between successive integer LSB
values. The LSB width for the ADC is VA/256. The ideal transfer characteristic is shown in Figure 20. 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.
111...111
111...000
|
|
ADC CODE
111...110
1 LSB = VA/256
011...111
000...010
|
000...001
000...000
0V
1 LSB
ANALOG INPUT
+VA-1 LSB
Figure 20. Ideal Transfer Characteristic
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Typical Application Circuit
A typical application of the ADC is shown in Figure 21. Power is provided in this example by the TI LP2950 lowdropout 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 ADC. Because the reference for the ADC 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 keep noise off the
ADC supply pin. Because of the ADC'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 also shown connected to a
microprocessor or DSP.
LP2950
0.1 PF
1 PF
VA
VIN
5V
1 PF
0.1 PF
SCLK
ADC081S101
CS
MICROPROCESSOR
DSP
SDATA
GND
Figure 21. Typical Application Circuit
Analog Input
An equivalent circuit for the ADC's input channel is shown in Figure 22. 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, the ESD diodes
should not be used to clamp the input signal.
The capacitor C1 in Figure 22 has a typical value of 4 pF, and is mainly the package pin capacitance. Resistor
R1 is the on resistance of the multiplexer and track / hold switch, and is typically 500Ω. Capacitor C2 is the ADC
sampling capacitor and is typically 26 pF. The ADC will deliver best performance when driven by a lowimpedance source to eliminate distortion caused by the charging of the sampling capacitance. This is especially
important when using the ADC to sample AC signals. Also important when sampling dynamic signals is an antialiasing filter.
VA
D1
R1
C2
26 pF
VIN
C1
4 pF
D2
Conversion Phase - Switch Open
Track Phase - Switch Closed
Figure 22. Equivalent Input Circuit
Digital Inputs and Outputs
The ADC digital inputs (SCLK and CS) are not limited by the same absolute maximum ratings as the analog
inputs. The digital input pins are instead limited to +5.25V with respect to GND, regardless of VA, the supply
voltage. This allows the ADC to be interfaced with a wide range of logic levels, independent of the supply
voltage.
14
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Modes of Operation
The ADC has two possible modes of operation: normal mode, and shutdown mode. The ADC enters normal
mode (and a conversion process is begun) when CS is pulled low. The device will enter shutdown mode if CS is
pulled high before the tenth falling edge of SCLK after CS is pulled low, or will stay in normal mode if CS remains
low. Once in shutdown mode, the device will stay there until CS is brought low again. By varying the ratio of time
spent in the normal and shutdown modes, a system may trade-off throughput for power consumption, with a
sample rate as low as zero.
Normal Mode
The fastest possible throughput is obtained by leaving the ADC in normal mode at all times, so there are no
power-up delays. To keep the device in normal mode continuously, CS must be kept low until after the 10th
falling edge of SCLK after the start of a conversion (remember that a conversion is initiated by bringing CS low).
If CS is brought high after the 10th falling edge, but before the 16th falling edge, the device will remain in normal
mode, but the current conversion will be aborted, and SDATA will return to TRI-STATE (truncating the output
word).
Sixteen SCLK cycles are required to read all of a conversion word from the device. After sixteen SCLK cycles
have elapsed, CS may be idled either high or low until the next conversion. If CS is idled low, it must be brought
high again before the start of the next conversion, which begins when CS is again brought low.
After sixteen SCLK cycles, SDATA returns to TRI-STATE. Another conversion may be started, after tQUIET has
elapsed, by bringing CS low again.
Shutdown Mode
Shutdown mode is appropriate for applications that either do not sample continuously, or it is acceptable to trade
throughput for power consumption. When the ADC is in shutdown mode, all of the analog circuitry is turned off.
To enter shutdown mode, a conversion must be interrupted by bringing CS back high anytime between the
second and tenth falling edges of SCLK, as shown in Figure 23. Once CS has been brought high in this manner,
the device will enter shutdown mode; the current conversion will be aborted and SDATA will enter TRI-STATE. If
CS is brought high before the second falling edge of SCLK, the device will not change mode; this is to avoid
accidentally changing mode as a result of noise on the CS line.
Figure 23. Entering Shutdown Mode
Figure 24. Entering Normal Mode
To exit shutdown mode, bring CS back low. Upon bringing CS low, the ADC will begin powering up (power-up
time is specified in the ADC081S101 Timing Specifications table). This power-up delay results in the first
conversion result being unusable. The second conversion performed after power-up, however, is valid, as shown
in Figure 24.
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If CS is brought back high before the 10th falling edge of SCLK, the device will return to shutdown mode. This is
done to avoid accidentally entering normal mode as a result of noise on the CS line. To exit shutdown mode and
remain in normal mode, CS must be kept low until after the 10th falling edge of SCLK. The ADC will be fully
powered-up after 16 SCLK cycles.
Power Management
The ADC takes time to power-up, either after first applying VA, or after returning to normal mode from shutdown
mode. This corresponds to one "dummy" conversion for any SCLK frequency within the specifications in this
document. After this first dummy conversion, the ADC will perform conversions properly. Note that the tQUIET time
must still be included between the first dummy conversion and the second valid conversion.
When the VA supply is first applied, the ADC may power up in either of the two modes: normal or shutdown. As
such, one dummy conversion should be performed after start-up, as described in the previous paragraph. The
part may then be placed into either normal mode or the shutdown mode, as described in Normal Mode and
Shutdown Mode.
When the ADC is operated continuously in normal mode, the maximum ensured throughput is fSCLK / 20 at the
maximum specified fSCLK. Throughput may be traded for power consumption by running fSCLK at its maximum
specified rate and performing fewer conversions per unit time, raising the ADC CS line after the 10th and before
the 15th fall of SCLK of each conversion. 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. Note that the curve of power
consumption vs. throughput is essentially 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 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. It is good practice
to use a 100Ω series 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.
REVISION HISTORY
Changes from Revision C (March 2013) to Revision D
•
Changed sentence in the "Using the ADC081S101" section ............................................................................................. 12
Changes from Revision B (March 2013) to Revision C
•
16
Page
Page
Changed layout of National Data Sheet to TI format .......................................................................................................... 16
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PACKAGE OPTION ADDENDUM
www.ti.com
24-Mar-2016
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
Lead/Ball Finish
MSL Peak Temp
(2)
(6)
(3)
Op Temp (°C)
Device Marking
(4/5)
ADC081S101 MWC
ACTIVE
WAFERSALE
YS
0
1
Green (RoHS
& no Sb/Br)
Call TI
Level-1-NA-UNLIM
-40 to 85
ADC081S101CIMF/NOPB
ACTIVE
SOT-23
DBV
6
1000
Green (RoHS
& no Sb/Br)
CU SN
Level-1-260C-UNLIM
-40 to 85
X03C
ADC081S101CIMFX/NOPB
ACTIVE
SOT-23
DBV
6
3000
Green (RoHS
& no Sb/Br)
CU SN
Level-1-260C-UNLIM
-40 to 85
X03C
ADC081S101CISD/NOPB
ACTIVE
WSON
NGF
6
1000
Green (RoHS
& no Sb/Br)
CU SN
Level-1-260C-UNLIM
-40 to 85
X3C
ADC081S101CISDX/NOPB
ACTIVE
WSON
NGF
6
4500
Green (RoHS
& no Sb/Br)
CU SN
Level-1-260C-UNLIM
-40 to 85
X3C
(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)
Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability
information and additional product content details.
TBD: The Pb-Free/Green conversion plan has not been defined.
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that
lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between
the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above.
Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight
in homogeneous material)
(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.
Addendum-Page 1
Samples
PACKAGE OPTION ADDENDUM
www.ti.com
24-Mar-2016
(6)
Lead/Ball Finish - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead/Ball Finish 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.
Addendum-Page 2
PACKAGE MATERIALS INFORMATION
www.ti.com
31-Oct-2013
TAPE AND REEL INFORMATION
*All dimensions are nominal
Device
Package Package Pins
Type Drawing
ADC081S101CIMF/NOPB SOT-23
SPQ
Reel
Reel
A0
Diameter Width (mm)
(mm) W1 (mm)
B0
(mm)
K0
(mm)
P1
(mm)
W
Pin1
(mm) Quadrant
DBV
6
1000
178.0
8.4
3.2
3.2
1.4
4.0
8.0
Q3
SOT-23
DBV
6
3000
178.0
8.4
3.2
3.2
1.4
4.0
8.0
Q3
ADC081S101CISD/NOPB WSON
NGF
6
1000
178.0
12.4
2.8
2.5
1.0
8.0
12.0
Q1
NGF
6
4500
330.0
12.4
2.8
2.5
1.0
8.0
12.0
Q1
ADC081S101CIMFX/NOP
B
ADC081S101CISDX/NOP
B
WSON
Pack Materials-Page 1
PACKAGE MATERIALS INFORMATION
www.ti.com
31-Oct-2013
*All dimensions are nominal
Device
Package Type
Package Drawing
Pins
SPQ
Length (mm)
Width (mm)
Height (mm)
ADC081S101CIMF/NOPB
SOT-23
DBV
6
1000
210.0
185.0
35.0
SOT-23
DBV
6
3000
210.0
185.0
35.0
WSON
NGF
6
1000
210.0
185.0
35.0
WSON
NGF
6
4500
367.0
367.0
35.0
ADC081S101CIMFX/NOP
B
ADC081S101CISD/NOPB
ADC081S101CISDX/NOP
B
Pack Materials-Page 2
MECHANICAL DATA
NGF0006A
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