1
ADS7818
ADS7818
ADS7818
DESCRIPTION
The ADS7818 is a 12-bit sampling analog-to-digital
converter (A/D) complete with sample/hold, internal
2.5V reference, and synchronous serial interface. Typi-
cal power dissipation is 11mW at a 500kHz through-
put rate. The device can be placed into a power down
mode which reduces dissipation to just 2.5mW. The
input range is zero to two times the reference voltage,
and the internal reference can be overdriven by an
external voltage.
Low power, small size, and high-speed make the
ADS7818 ideal for battery operated systems such as
wireless communication devices, portable multi-chan-
nel data loggers, and spectrum analyzers. The serial
interface also provides low-cost isolation for remote
data acquisition. The ADS7818 is available in a plas-
tic mini-DIP-8 or an MSOP-8 package and is guaran-
teed over the 40
C to +85
C temperature range.
12-Bit High Speed Low Power Sampling
ANALOG-TO-DIGITAL CONVERTER
FEATURES
q
500kHz THROUGHPUT RATE
q
2.5V INTERNAL REFERENCE
q
LOW POWER: 11mW
q
SINGLE SUPPLY +5V OPERATION
q
DIFFERENTIAL INPUT
q
SERIAL INTERFACE
q
GUARANTEED NO MISSING CODES
q
MINI-DIP-8 AND MSOP-8
q
UNIPOLAR INPUT RANGE
International Airport Industrial Park Mailing Address: PO Box 11400, Tucson, AZ 85734 Street Address: 6730 S. Tucson Blvd., Tucson, AZ 85706 Tel: (520) 746-1111
Twx: 910-952-1111 Internet: http://www.burr-brown.com/ Cable: BBRCORP Telex: 066-6491 FAX: (520) 889-1510 Immediate Product Info: (800) 548-6132
APPLICATIONS
q
BATTERY OPERATED SYSTEMS
q
DIGITAL SIGNAL PROCESSING
q
HIGH SPEED DATA ACQUISITION
q
WIRELESS COMMUNICATION SYSTEMS
1998 Burr-Brown Corporation
PDS-1408B
Printed in U.S.A. May, 2000
SAR
CLK
Serial
Interface
Comparator
S/H Amp
DATA
+In
In
CDAC
Internal
+2.5V Ref
Buffer
V
REF
CONV
10k
30%
For most current data sheet and other product
information, visit www.burr-brown.com
2
ADS7818
SPECIFICATIONS
At T
A
= 40
C to +85
C, +V
CC
= +5V, f
SAMPLE
= 500kHz, f
CLK
= 16 f
SAMPLE
, internal reference, unless otherwise specified.
The information provided herein is believed to be reliable; however, BURR-BROWN assumes no responsibility for inaccuracies or omissions. BURR-BROWN
assumes no responsibility for the use of this information, and all use of such information shall be entirely at the user's own risk. Prices and specifications are subject
to change without notice. No patent rights or licenses to any of the circuits described herein are implied or granted to any third party. BURR-BROWN does not
authorize or warrant any BURR-BROWN product for use in life support devices and/or systems.
ADS7818P, E
ADS7818PB, EB
PARAMETER
CONDITIONS
MIN
TYP
MAX
MIN
TYP
MAX
UNITS
ANALOG INPUT
Full-Scale Input Span
(1)
+In (In)
0
5
T
T
V
Absolute Input Range
+In
0.2
V
CC
+0.2
T
T
V
In
0.2
+0.2
T
T
V
Capacitance
15
T
pF
Leakage Current
1
T
A
SYSTEM PERFORMANCE
Resolution
12
T
Bits
No Missing Codes
12
T
Bits
Integral Linearity Error
1
2
0.5
1
LSB
(2)
Differential Linearity Error
0.8
0.5
1
LSB
Offset Error
2
5
1
T
LSB
Gain Error
(3)
25
C
12
30
7
15
LSB
40
C to +85
C
50
35
LSB
Common-Mode Rejection
DC, 0.2Vp-p
70
T
dB
1MHz, 0.2Vp-p
50
T
dB
Noise
150
T
Vrms
Power Supply Rejection
Worst Case
, +V
CC
= 5V
5%
1.2
T
LSB
SAMPLING DYNAMICS
Conversion Time
1.625
T
s
Acquisition Time
0.350
T
s
Throughput Rate
500
T
kHz
Aperture Delay
5
T
ns
Aperture Jitter
30
T
ps
Step Response
350
T
ns
DYNAMIC CHARACTERISTICS
Signal-to-Noise Ratio
V
IN
= 5Vp-p at 100kHz
72
T
dB
Total Harmonic Distortion
(4)
V
IN
= 5Vp-p at 100kHz
78
72
82
75
dB
Signal-to-(Noise+Distortion)
V
IN
= 5Vp-p at 100kHz
68
70
70
72
dB
Spurious Free Dynamic Range
V
IN
= 5Vp-p at 100kHz
72
78
75
82
dB
Usable Bandwidth
SINAD > 68dB
350
T
kHz
REFERENCE OUTPUT
Voltage
I
OUT
= 0
2.475
2.50
2.525
2.48
T
2.52
V
Source Current
(5)
Static Load
50
T
A
Drift
I
OUT
= 0
20
T
ppm /
C
Line Regulation
4.75V
V
CC
5.25V
0.6
T
mV
REFERENCE INPUT
Range
2.0
2.55
T
T
V
Resistance
(6)
to Internal Reference Voltage
10
T
T
T
k
DIGITAL INPUT/OUTPUT
Logic Family
CMOS
T
Logic Levels:
V
IH
|I
IH
|
+5
A
3.0
V
CC
+0.3
T
T
V
V
IL
|I
IL
|
+5
A
0.3
0.8
T
T
V
V
OH
I
OH
= 500
A
3.5
T
T
V
V
OL
I
OL
= 500
A
0.4
T
T
V
Data Format
Straight Binary
T
POWER SUPPLY REQUIREMENT
+V
CC
Specified Performance
4.75
5.25
T
T
V
Quiescent Current
f
SAMPLE
= 500kHz
2.2
T
mA
Power Down
0.5
T
mA
Power Dissipation
f
SAMPLE
= 500kHz
11
20
T
T
mW
Power Down
2.5
T
mW
TEMPERATURE RANGE
Specified Performance
40
+85
T
T
C
T
Specifications same as ADS7818P,E.
NOTES: (1) Ideal input span, does not include gain or offset error. (2) LSB means Least Significant Bit, with V
REF
equal to +2.5V, one LSB is 1.22mV. (3) Measured
relative to an ideal, full-scale input (+In (In)) of 4.999V. Thus, gain error includes the error of the internal voltage reference. (4) Calculated on the first nine
harmonics of the input frequency. (5) If the internal reference is required to source current to an external load, the reference voltage will change due to the internal
10k
resistor. (6) Can vary
30%.
3
ADS7818
+V
CC
to GND ............................................................................ 0.3V to 6V
Analog Inputs to GND .............................................. 0.3V to (V
CC
+ 0.3V)
Digital Inputs to GND ............................................... 0.3V to (V
CC
+ 0.3V)
Power Dissipation .......................................................................... 325mW
Maximum Junction Temperature ................................................... +150
C
Operating Temperature Range ......................................... 40
C to +85
C
Storage Temperature Range .......................................... 65
C to +150
C
Lead Temperature (soldering, 10s) ............................................... +300
C
NOTE: (1) Stresses above those listed under "Absolute Maximum Ratings" may
cause permanent damage to the device. Exposure to absolute maximum condi-
tions for extended periods may affect device reliability.
ELECTROSTATIC
DISCHARGE SENSITIVITY
Electrostatic discharge can cause damage ranging from per-
formance degradation to complete device failure. Burr-
Brown Corporation recommends that all integrated circuits
be handled and stored using appropriate ESD protection
methods.
ESD damage can range from subtle performance degrada-
tion 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
published specifications.
ABSOLUTE MAXIMUM RATINGS
(1)
PIN CONFIGURATION
Top View
1
2
3
4
8
7
6
5
+V
CC
CLK
DATA
CONV
V
REF
+In
In
GND
ADS7818
Plastic Mini-DIP-8
PIN
NAME
DESCRIPTION
1
V
REF
Reference Output. Decouple to ground with a 0.1
F ceramic capacitor and a 2.2
F tantalum capacitor.
2
+In
Non-Inverting Input.
3
In
Inverting Input. Connect to ground or to remote ground sense point.
4
GND
Ground.
5
CONV
Convert Input. Controls the sample/hold mode, start of conversion, start of serial data transfer, type of serial transfer, and power
down mode. See the Digital Interface section for more information.
6
DATA
Serial Data Output. The 12-bit conversion result is serially transmitted most significant bit first with each bit valid on the rising edge
of CLK. By properly controlling the CONV input, it is possibly to have the data transmitted least significant bit first. See the Digital
Interface section for more information.
7
CLK
Clock Input. Synchronizes the serial data transfer and determines conversion speed.
8
+V
CC
Power Supply. Decouple to ground with a 0.1
F ceramic capacitor and a 10
F tantalum capacitor.
PIN ASSIGNMENTS
1
2
3
4
8
7
6
5
+V
CC
CLK
DATA
CONV
V
REF
+In
In
GND
ADS7818
MSOP-8
PACKAGE/ORDERING INFORMATION
MAXIMUM
MAXIMUM
INTEGRAL
DIFFERENTIAL
LINEARITY
LINEARITY
PACKAGE
SPECIFICATION
ERROR
ERROR
DRAWING
TEMPERATURE
PACKAGE
ORDERING
TRANSPORT
PRODUCT
(LSB)
(LSB)
PACKAGE
NUMBER
(1)
RANGE
MARKING
(2)
NUMBER
(3)
MEDIA
ADS7818E
2
N/S
(4)
MSOP-8
337
40
C to +85
C
A18
ADS7818E/250
Tape and Reel
"
"
"
"
"
"
"
ADS7818E/2K5
Tape and Reel
ADS7818EB
1
1
MSOP-8
337
40
C to +85
C
A18
ADS7818EB/250
Tape and Reel
"
"
"
"
"
"
"
ADS7818EB/2K5
Tape and Reel
ADS7818P
2
N/S
(4)
Plastic DIP-8
006
40
C to +85
C
ADS7818P
ADS7818P
Rails
ADS7818PB
1
1
"
"
"
ADS7818PB
ADS7818PB
Rails
NOTE: (1) For detail drawing and dimension table, please see end of data sheet or Package Drawing File on Web. (2) Performance Grade information is marked
on the reel. (3) Models with a slash(/) are available only in Tape and reel in quantities indicated (e.g. /250 indicates 250 units per reel, /2K5 indicates 2500 devices
per reel). Ordering 2500 pieces of "ADS7818E/2K5" will get a single 2500-piece Tape and Reel. For detailed Tape and Reel mechanical information, refer to the
www.burr-brown.com web site under Applications and Tape and Reel Orientation and Dimensions. (4) N/S = Not Specified, typical only. However, 12-Bits no missing
codes is guaranteed over temperature.
4
ADS7818
TYPICAL PERFORMANCE CURVES
At T
A
= +25
C, V
CC
= +5V, f
SAMPLE
= 500kHz, f
CLK
= 16 f
SAMPLE
, and internal +2.5V reference, unless otherwise specified.
CHANGE IN INTEGRAL LINEARITY and
DIFFERENTIAL LINEARITY vs SAMPLE RATE
400
100
600
200
300
500
Sample Rate (kHz)
Delta from f
SAMPLE
= 500kHz (LSB)
0.3
0.4
0.3
0.2
0.1
0.0
0.1
0.2
Change in Differential
Linearity (LSB)
Change in Integral
Linearity (LSB)
CHANGE IN OFFSET vs TEMPERATURE
20
40
100
20
0
40
Temperature (
C)
Delta from 25
C (LSB)
0.4
2.0
1.6
1.2
0.8
0.4
0.0
60
80
POWER-DOWN SUPPLY CURRENT
vs TEMPERATURE
20
40
100
20
0
40
Temperature (C)
Power-down Supply Current (A)
390
470
440
430
420
410
400
450
460
60
80
SUPPLY CURRENT vs TEMPERATURE
20
40
100
20
0
40
Temperature (C)
Supply Current (mA)
1.6
2.3
2.1
2.0
1.9
1.8
1.7
2.2
60
80
f
SAMPLE
= 500kHz
f
SAMPLE
= 125kHz
SUPPLY CURRENT vs SAMPLE RATE
400
100
600
200
300
500
Sample Rate (kHz)
Supply Current (mA)
1.7
2.4
2.3
2.2
2.1
2.0
1.9
1.8
CHANGE IN FULL-SCALE ERROR
vs TEMPERATURE
20
40
100
20
0
40
Temperature (
C)
Delta from 25
C (LSB)
10
2
0
2
4
6
8
60
80
5
ADS7818
TYPICAL PERFORMANCE CURVES
(Cont.)
At T
A
= +25
C, V
CC
= +5V, f
SAMPLE
= 500kHz, f
CLK
= 16 f
SAMPLE
, and internal +2.5V reference, unless otherwise specified.
POWER SUPPLY REJECTION
vs POWER SUPPLY RIPPLE FREQUENCY
1
10
100
1k
10k
100k
1M
Power Supply Ripple Frequency (Hz)
Power Supply Rejection (mV/V)
30
25
20
15
10
5
0
0
FREQUENCY SPECTRUM
(4096 Point FFT; f
IN
= 10.9kHz, 0.2dB)
0
250
62.5
187.5
125
Frequency (kHz)
Amplitude (dB)
120
100
80
60
40
20
0
FREQUENCY SPECTRUM
(4096 Point FFT; f
IN
= 102kHz, 0.2dB)
Amplitude (dB)
100
80
60
40
20
0
250
62.5
187.5
125
Frequency (kHz)
120
CHANGE IN FULL-SCALE ERROR
vs EXTERNAL REFERENCE VOLTAGE
2.3
2.0
2.5
2.1
2.2
2.4
External Reference Voltage (V)
Delta from V
REF
= 2.5V (mV)
1.2
0.2
0.4
0.6
0.8
1.0
0.2
0.0
CHANGE IN OFFSET
vs EXTERNAL REFERENCE VOLTAGE
2.5
1.9
3.1
2.1
2.3
2.7
2.9
External Reference Voltage (V)
Delta from V
REF
= 2.5V (mV)
0.4
0.5
0.0
0.1
0.2
0.3
0.1
0.2
0.3
0.4
PEAK-TO-PEAK NOISE
vs EXTERNAL REFERENCE VOLTAGE
2.3
2.0
2.5
2.1
2.2
2.4
External Reference Voltage (LSB)
Peak-to-Peak Noise (LSB)
0.40
0.70
0.65
0.60
0.55
0.50
0.45
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