ADS8321
SBAS123B – SEPTEMBER 1999 – REVISED SEPTEMBER 2004
16-Bit, High Speed, MicroPower Sampling
ANALOG-TO-DIGITAL CONVERTER
FEATURES
q
BIPOLAR INPUT RANGE
q
100kHz SAMPLING RATE
q
MICRO POWER:
4.5mW at 100kHz
1mW at 10kHz
q
POWER DOWN: 3
µ
A max
q
MSOP-8 PACKAGE
q
PIN-COMPATIBLE TO ADS7816 AND ADS7822
q
SERIAL (SPI/SSI) INTERFACE
DESCRIPTION
The ADS8321 is a 16-bit sampling analog-to-digital con-
verter (ADC) with tested specifications over a 4.75V to
5.25V supply range. It requires very little power even when
operating at the full 100kHz data rate. At lower data rates,
the high speed of the device enables it to spend most of its
time in the power-down mode—the average power dissipa-
tion is less than 1mW at 10kHz data rate.
The ADS8321 also features a synchronous serial (SPI/SSI
compatible) interface, and a differential input. The refer-
ence voltage can be set to any level within the range of
500mV to V
CC
/2.
Ultra-low power and small size make the ADS8321 ideal
for portable and battery-operated systems. It is also a
perfect fit for remote data acquisition modules, simulta-
neous multi-channel systems, and isolated data acquisi-
tion. The ADS8321 is available in an MSOP-8 package.
APPLICATIONS
q
q
q
q
BATTERY OPERATED SYSTEMS
REMOTE DATA ACQUISITION
ISOLATED DATA ACQUISITION
SIMULTANEOUS SAMPLING,
MULTI-CHANNEL SYSTEMS
q
INDUSTRIAL CONTROLS
q
ROBOTICS
q
VIBRATION ANALYSIS
SAR
V
REF
ADS8321
D
OUT
+In
CDAC
–In
S/H Amp
Comparator
CS/SHDN
Serial
Interface
DCLOCK
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 Texas Instruments
standard warranty. Production processing does not necessarily include
testing of all parameters.
Copyright © 1999-2004, Texas Instruments Incorporated
www.ti.com
ABSOLUTE MAXIMUM RATINGS
(1)
V
CC
....................................................................................................... +6V
Analog Input ............................................................. –0.3V to (V
CC
+ 0.3V)
Logic Input ............................................................................... –0.3V to 6V
Case Temperature ......................................................................... +100°C
Junction Temperature .................................................................... +150°C
Storage Temperature ..................................................................... +125°C
External Reference Voltage .............................................................. +5.5V
NOTE: (1) Stresses above these ratings may permanently damage the device.
ELECTROSTATIC
DISCHARGE SENSITIVITY
This integrated circuit can be damaged by ESD. Texas Instruments
recommends that all integrated circuits be handled with appropriate
precautions. Failure to observe proper handling and installation proce-
dures can cause damage.
ESD damage can range from subtle performance degradation to
complete device failure. Precision integrated circuits may be more
susceptible to damage because very small parametric changes could
cause the device not to meet its published specifications.
PACKAGE/ORDERING INFORMATION
(1)
MAXIMUM
INTEGRAL
LINEARITY
ERROR
(%)
0.018
NO
MISSING
CODE
ERROR
(LSB)
14
PRODUCT
ADS8321E
PACKAGE-LEAD
MSOP-8
PACKAGE
DESIGNATOR
(1)
DGK
SPECIFICATION
TEMPERATURE
RANGE
–40°C to +85°C
PACKAGE
MARKING
A21
ORDERING
NUMBER
ADS8321E/250
ADS8321E/2K5
ADS8321EB/250
ADS8321EB/2K5
TRANSPORT
MEDIA, QUANTITY
Tape and Reel, 250
Tape and Reel, 2500
Tape and Reel, 250
Tape and Reel, 2500
"
ADS8321EB
"
0.012
"
15
"
MSOP-8
"
DGK
"
–40°C to +85°C
"
A21
"
"
"
"
"
"
"
NOTE: (1) For the most current package and ordering information, see the Package Option Addendum located at the end of this data sheet.
PIN CONFIGURATION
Top View
MSOP
PIN ASSIGNMENTS
PIN
1
2
3
4
NAME
V
REF
+In
–In
GND
CS/SHDN
D
OUT
DESCRIPTION
Reference Input
Non Inverting Input
Inverting Input
Ground
Chip Select when LOW, Shutdown Mode when
HIGH.
The serial output data word is comprised of 16
bits of data. In operation the data is valid on the
falling edge of DCLOCK. The second clock
pulse after the falling edge of CS enables the
serial output. After one null bit, data is valid for
the next 16 edges.
Data Clock synchronizes the serial data transfer
and determines conversion speed.
Power Supply.
V
REF
+In
–In
GND
1
2
ADS8321
3
4
8
7
6
5
+V
CC
DCLOCK
5
6
D
OUT
CS/SHDN
7
8
DCLOCK
+V
CC
2
ADS8321
www.ti.com
SBAS123B
SPECIFICATIONS: +V
CC
= +5V
At –40°C to +85°C, V
REF
= +2.5V, –In = 2.5V, f
SAMPLE
= 100kHz, and f
CLK
= 24 • f
SAMPLE
, unless otherwise specified.
ADS8321E
PARAMETER
RESOLUTION
ANALOG INPUT
Full-Scale Input Span
Absolute Input Range
Capacitance
Leakage Current
SYSTEM PERFORMANCE
No Missing Codes
Integral Linearity Error
Offset Error
Offset Temperature Drift
Gain Error, Positive
Negative
Gain Temperature Drift
Noise
Common-Mode Rejection Ratio
Power Supply Rejection Ratio
SAMPLING DYNAMICS
Conversion Time
Acquisition Time
Throughput Rate
Clock Frequency Range
DYNAMIC CHARACTERISTICS
Total Harmonic Distortion
SINAD
Spurious Free Dynamic Range
SNR
REFERENCE INPUT
Voltage Range
Resistance
Current Drain
f
SAMPLE
= 10kHz
CS = V
CC
DIGITAL INPUT/OUTPUT
Logic Family
Logic Levels:
V
IH
V
IL
V
OH
V
OL
Data Format
POWER SUPPLY REQUIREMENTS
V
CC
V
CC
Range
(2)
Quiescent Current
Power Dissipation
Power Down
TEMPERATURE RANGE
Specified Performance
✻
Specifications same as ADS8321E.
NOTES: (1) LSB means Least Significant Bit. (2) See Typical Performance Curves for more information. (3) f
CLK
= 2.4MHz, CS = V
CC
for 216 clock cycles out
of every 240. (4) See the Power Dissipation section for more information regarding lower sample rates.
V
IN
= 5Vp-p at 10kHz
V
IN
= 5Vp-p at 10kHz
V
IN
= 5Vp-p at 10kHz
14
±0.008
±0.4
±1
±0.018
±2
±0.05
±0.05
±0.3
60
80
3
16
4.5
0.024
–84
82
84
85
0.5
CS = GND, f
SAMPLE
= 0Hz
CS = V
CC
5
5
40
0.8
0.1
CMOS
I
IH
= +5µA
I
IL
= +5µA
I
OH
= –250µA
I
OL
= 250µA
3.0
–0.3
4.0
V
CC
+ 0.3
0.8
✻
✻
✻
✻
✻
✻
✻
✻
✻
✻
✻
✻
✻
✻
✻
✻
✻
V
V
µA
µA
mW
µA
°C
V
CC
/2
✻
✻
✻
✻
✻
✻
✻
✻
✻
✻
V
V
V
V
100
2.9
✻
✻
–86
84
86
87
✻
✻
✻
✻
✻
✻
✻
✻
+In – (–In)
+In
–In
–V
REF
–0.1
–0.1
25
1
15
±0.006
±0.2
✻
±0.012
±1
±0.024
±0.024
CONDITIONS
MIN
TYP
MAX
16
+V
REF
V
CC
+ 0.1
+4.0
✻
✻
✻
✻
✻
MIN
ADS8321EB
TYP
MAX
✻
✻
✻
✻
UNITS
Bits
V
V
V
pF
nA
Bits
% of FSR
mV
µV/°C
%
%
ppm/°C
µVrms
dB
LSB
(1)
Clk Cycles
Clk Cycles
kHz
MHz
dB
dB
dB
dB
V
GΩ
GΩ
µA
µA
µA
+4.7V < V
CC
< 5.25V
80
3
✻
0.4
Binary Two’s Complement
Specified Performance
4.75
2.7
1100
250
5.5
0.3
–40
5.25
5.25
1700
8.5
3
+85
f
SAMPLE
= 10kHz
(3, 4)
CS = V
CC
ADS8321
SBAS123B
www.ti.com
3
TYPICAL PERFORMANCE CURVES
At T
A
= +25°C, V
CC
= +5V, V
REF
= +2.5V, f
SAMPLE
= 100kHz, f
CLK
= 24 • f
SAMPLE
, unless otherwise specified.
FREQUENCY SPECTRUM
(8192 Point FFT, f
IN
= 10.03kHz, –0.3dB)
0
–20
–40
Amplitude (dB)
INTEGRAL LINEARITY ERROR vs CODE (+25°C)
3
2
Integral Linearity Error (LSB)
1
0
–1
–2
–3
–4
–5
–6
–60
–80
–100
–120
–140
–160
–180
0
10
20
30
40
50
Frequency (kHz)
0000
H
4000
H
7FF9
H
Hex Code
C000
H
FFFD
H
DIFFERENTIAL LINEARITY ERROR vs CODE (+25°C)
3.0
1400
1200
SUPPLY CURRENT vs TEMPERATURE
Differential Linearity Error (LSB)
2.5
Supply Current (µA)
2.0
1.5
1.0
0.5
0
–0.5
–1.0
–1.5
0000
H
3FFF
H
7FFC
H
Hex Code
C000
H
FFFD
H
1000
800
600
400
200
0
–50
0
50
Temperature (°C)
100
POWER-DOWN SUPPLY CURRENT
vs TEMPERATURE
600
500
400
5V
300
200
100
0
–50
–25
0
25
50
75
100
Temperature (°C)
Quiescent Current (mA)
Supply Current (nA)
1.20
1.10
1.00
0.90
0.80
0.70
0.60
2.0
2.5
QUIESCENT CURRENT vs V
CC
3.0
3.5
4.0
4.5
5.0
5.5
V
CC
(V)
4
ADS8321
www.ti.com
SBAS123B
TYPICAL PERFORMANCE CURVES
(Cont.)
At T
A
= +25°C, V
CC
= +5V, V
REF
= +2.5V, f
SAMPLE
= 100kHz, f
CLK
= 24 • f
SAMPLE
, unless otherwise specified.
MAXIMUM SAMPLE RATE vs V
CC
1000
90
SIGNAL-TO-NOISE AND SIGNAL-TO-(NOISE + DISTORTION)
vs INPUT FREQUENCY
SNR
85
100
SNR and SINAD (dB)
Sample Rate (kHz)
80
SINAD
75
10
70
1
1
2
3
V
CC
(V)
4
5
65
0.1
1
10
100
Input Frequency (kHz)
SPURIOUS FREE DYNAMIC RANGE AND
TOTAL HARMONIC DISTORTION vs INPUT FREQUENCY
90
SFDR
30
35
REFERENCE CURRENT vs SAMPLE RATE
2.5V
Reference Current (µA)
85
SNR and SINAD (dB)
25
20
15
10
5
0
1.25V
THD
80
75
70
65
0.1
1
10
Input Frequency (kHz)
100
0
20
40
60
80
100
Sample Rate (kHz)
120
140
NOISE vs REFERENCE VOLTAGE
18
16
Peak-to-Peak Noise (LSB)
10
15
CHANGE IN GAIN vs REFERENCE VOLTAGE
Change in Gain (LSB)
14
12
10
8
6
4
2
0
0.1
1
Reference Voltage (V)
10
5
0
–5
–10
–15
0
0.5
1.0
1.5
2.0
Reference Voltage (V)
2.5
3.0
ADS8321
SBAS123B
www.ti.com
5
