®
ADS7811
1
ADS7811
16-Bit 250kHz Sampling CMOS
ANALOG-to-DIGITAL CONVERTER
DESCRIPTION
The ADS7811 is a complete 16-bit sampling analog-
to-digital (A/D) converter featuring excellent AC
performance and a 250kHz throughput rate. The de-
sign includes a 16-bit capacitor-based SAR A/D
converter with an inherent sample and hold (S/H), a
precision reference, and an internal clock. Spurious-
free dynamic range with a 100kHz full-scale sinewave
input is typically greater than 100dB. The
±
2.5V input
range allows development of precision systems using
only
±
5V supplies. The converter is available in a
28-lead SOIC package specified for operation over
the industrial 25
°
C to +85
°
C temperature range.
ADS7811
®
FEATURES
q
250kHz SAMPLING RATE
q
COMPLETE WITH S/H, REF, CLOCK, ETC.
q
96dB min SFDR WITH 100kHz INPUT
q
84dB min SINAD
q
±
2.5V INPUT RANGE
q
28-LEAD SOIC
CDAC
Output
Latches
and
Three
State
Drivers
Comparator
Buffer
5k
REF Out/In
±2.5V Input
Successive Approximation Register and Control Logic
Clock
BUSY
CS
R/C
Internal
+2.5V Ref
Parallel
Data
Bus
APPLICATIONS
q
WIRELESS BASE STATIONS
q
SPECTRUM ANALYSIS
q
IMAGING SYSTEMS
q
DATA ACQUISITION
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/ · FAXLine: (800) 548-6133 (US/Canada Only) · Cable: BBRCORP · Telex: 066-6491 · FAX: (520) 889-1510 · Immediate Product Info: (800) 548-6132
©
1997 Burr-Brown Corporation
PDS-1300A
Printed in U.S.A. November, 1997
2
®
ADS7811
RESOLUTION
16
Bits
ANALOG INPUT
Voltage Range
±
2.5V
V
Impedance
After Input Capacitor is Charged
100
M
Capacitance
30
pF
THROUGHPUT SPEED
Conversion Cycle
Acquire and Convert
4.0
µ
s
Throughput Rate
250
kHz
DC ACCURACY
Integral Linearity Error
±
4
LSB
(1)
No Missing Codes
15
Bits
Transition Noise
(2)
0.8
LSB
Full Scale Error
(3)
±
0.5
%
Full Scale Error Drift
±
7
ppm/
°
C
Full Scale Error
(3)
External 2.5000V Reference
±
0.2
%
Full Scale Error Drift
External 2.5000V Reference
2
ppm/
°
C
Bipolar Zero Error
±
10
mV
Bipolar Zero Error Drift
±
2
ppm/
°
C
Power Supply Sensitivity
+V
S
±
5%, V
S
±
5%
±
6
±
16
LSB
AC ACCURACY
Spurious-Free Dynamic Range
f
IN
= 100kHz
96
100
dB
(4)
Total Harmonic Distortion
f
IN
= 100kHz
98
96
dB
Signal-to-(Noise+Distortion)
f
IN
= 100kHz
84
87
dB
60dB Input
28
dB
Signal-to-Noise
f
IN
= 100kHz
84
87
dB
Usable Bandwidth
(5)
1
MHz
Aperture Delay
40
ns
REFERENCE
Internal Reference Voltage
2.48
2.5
2.52
V
Internal Reference Source Current
1
µ
A
Internal Reference Drift
15
ppm/
°
C
External Reference Voltage Range
2.5
V
External Reference Current Drain
V
REF
= +2.5V
100
µ
A
DIGITAL INPUTS
Logic Levels
V
IL
0.3
+0.8
V
V
IH
+2.8
+V
S
+0.3V
V
I
IL
±
10
µ
A
I
IH
±
10
µ
A
DIGITAL OUTPUTS
Data Format
Data Coding
V
OL
I
SINK
= 1.6mA
+0.4
V
V
OH
I
SOURCE
= 200
µ
A
+4
V
Leakage Current
High-Z State,
±
5
µ
A
V
OUT
= 0V to V
DIG
Output Capacitance
High-Z State
15
pF
DIGITAL TIMING
Bus Access Time
83
ns
Bus Relinquish Time
83
ns
POWER SUPPLIES
+V
S
+4.75
+5
+5.25
V
V
S
5.25
5
4.75
V
+I
S
+30
mA
I
S
10
mA
Power Dissipation
200
250
mW
TEMPERATURE RANGE
Specified Performance
25
+85
°
C
Storage
55
+125
°
C
NOTES: (1) LSB means Least Significant Bit. For the 16-bit,
±
2.5V input ADS7811, one LSB is 76
µ
V. (2) Typical rms noise at worst case transitions and
temperatures. (3) Full scale error is the worst case of Full Scale or +Full Scale untrimmed deviation from ideal first and last code transitions, divided by the transition
voltage (not divided by the full-scale range) and includes the effect of offset error. (4) All specifications in dB are referred to a full-scale
±
2.5V input. (5) Usable
Bandwidth defined as Full-Scale input frequency at which Signal-to-(Noise+Distortion) degrades to 60dB, or 10 bits of accuracy.
SPECIFICATIONS
At T
A
= 25
°
C to +85
°
C, f
S
= 250kHz, +V
S
= +5V, and V
S
= 5V, using internal reference, unless otherwise specified.
ADS7811U
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Parallel 16 bits
Binary Two's Complement
®
ADS7811
3
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.
ABSOLUTE MAXIMUM RATINGS
Analog Inputs: V
IN
.............................................. V
S
0.3V to +V
S
+ 0.3V
REF ................................................... 0.3V to +V
S
+ 0.3V
CAP ............................................... Indefinite Short to GND
Momentary Short to +V
S
+V
S
......................................................................................................... 7V
V
S
...................................................................................................... 7V
Digital Inputs .............................................................. 0.3V to +V
S
+ 0.3V
Maximum Junction Temperature ................................................... +165
°
C
Internal Power Dissipation ............................................................. 825mW
Lead Temperature (soldering, 10s) ................................................ +300
°
C
ELECTROSTATIC
DISCHARGE SENSITIVITY
This integrated circuit can be damaged by ESD. Burr-Brown
recommends that all integrated circuits be handled with
appropriate precautions. Failure to observe proper handling
and installation procedures 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
DRAWING
TEMPERATURE
PRODUCT
PACKAGE
NUMBER
(1)
RANGE
ADS7811U
28-Pin SOIC
217
25
°
C to +85
°
C
NOTE: (1) For detailed drawing and dimension table, please see end of data
sheet, or Appendix C of Burr-Brown IC Data Book.
PACKAGE/ORDERING INFORMATION
4
®
ADS7811
PIN #
NAME
DESCRIPTION
1
V
IN
Analog Input. Full-scale input range is
±
2.5V.
2
GND
Ground.
3
REF
Reference Input/Output. Outputs internal reference of +2.5V nominal. Can also be driven by external system reference. In
both cases, connect to ground with a 0.1
µ
F ceramic capacitor in parallel with 2.2
µ
F tantalum capacitor.
4
CAP
Reference compensation capacitor. Use a parallel combination of a 0.1
µ
F ceramic capacitor and a 2.2
µ
F tantalum capacitor.
5
GND
Ground.
6
D15 (MSB)
Data Bit 15. Most Significant Bit (MSB) of conversion results. Hi-Z state when CS is HIGH, when R/C is LOW or when a
conversion is in progress.
7
D14
Data Bit 14. Hi-Z state when CS is HIGH, when R/C is LOW or when a conversion is in progress.
8
D13
Data Bit 13. Hi-Z state when CS is HIGH, when R/C is LOW or when a conversion is in progress.
9
D12
Data Bit 12. Hi-Z state when CS is HIGH, when R/C is LOW or when a conversion is in progress.
10
D11
Data Bit 11. Hi-Z state when CS is HIGH, when R/C is LOW or when a conversion is in progress.
11
D10
Data Bit 10. Hi-Z state when CS is HIGH, when R/C is LOW or when a conversion is in progress.
12
D9
Data Bit 9. Hi-Z state when CS is HIGH, when R/C is LOW or when a conversion is in progress.
13
D8
Data Bit 8. Hi-Z state when CS is HIGH, when R/C is LOW or when a conversion is in progress.
14
GND
Ground.
15
D7
Data Bit 7. Hi-Z state when CS is HIGH, when R/C is LOW or when a conversion is in progress.
16
D6
Data Bit 6. Hi-Z state when CS is HIGH, when R/C is LOW or when a conversion is in progress.
17
D5
Data Bit 5. Hi-Z state when CS is HIGH, when R/C is LOW or when a conversion is in progress.
18
D4
Data Bit 4. Hi-Z state when CS is HIGH, when R/C is LOW or when a conversion is in progress.
19
D3
Data Bit 3. Hi-Z state when CS is HIGH, when R/C is LOW or when a conversion is in progress.
20
D2
Data Bit 2. Hi-Z state when CS is HIGH, when R/C is LOW or when a conversion is in progress.
21
D1
Data Bit 1. Hi-Z state when CS is HIGH, when R/C is LOW or when a conversion is in progress.
22
D0 (LSB)
Data Bit 0. Least Significant Bit (LSB) of conversion results. Hi-Z state when CS is HIGH, when R/C is LOW or when a
conversion is in progress.
23
V
S
Negative supply input. Nominally 5V. Decouple to analog ground with 0.1
µ
F ceramic and 10
µ
F tantalum capacitors.
24
R/C
Read/convert input. With R/C HIGH, CS going LOW will enable the output data bits if a conversion is not in progress. With
R/C LOW, CS going LOW will start a conversion if one is not already in progress.
25
CS
Chip select. With R/C LOW, CS going LOW will initiate a conversion if one is not already in progress. With R/C HIGH, CS
going LOW will enable the output data bits if a conversion is not in progress.
26
BUSY
Busy output. Falls when a conversion is started, and remains LOW until the conversion is completed. With CS LOW and
R/C HIGH, output data will be valid when BUSY rises, so that the rising edge can be used to latch the data. CS or R/C must
be HIGH within 250ns after BUSY rises or another conversion will start without time for signal acquisition.
27
+V
S
Positive supply input. Nominally +5V. Connect directly to pin 28.
28
+V
S
Positive supply input. Nominally +5V. Connect directly to pin 27. Decouple to ground with 0.1
µ
F ceramic and 10
µ
F
tantalum capacitors.
TABLE I. Pin Assignments.
PIN CONFIGURATION
Top View
SOIC
+V
S
+V
S
BUSY
CS
R/C
V
S
D0 (LSB)
D1
D2
D3
D4
D5
D6
D7
V
IN
GND
REF
CAP
GND
D15 (MSB)
D14
D13
D12
D11
D10
D9
D8
GND
1
2
3
4
5
6
7
8
9
10
11
12
13
14
28
27
26
25
24
23
22
21
20
19
18
17
16
15
ADS7811
®
ADS7811
5
TYPICAL PERFORMANCE CURVES
At T
A
= 25
°
C to +85
°
C, f
S
= 250kHz, +V
S
= +5V, and V
S
= 5V, using internal reference, unless otherwise specified.
140
120
100
80
60
40
20
0
FREQUENCY SPECTRUM
(4096 Point FFT; f
IN
= 9.9kHz, 0.5dB)
0
125
25
75
100
50
Frequency (kHz)
Amplitude (dB)
140
120
100
80
60
40
20
0
FREQUENCY SPECTRUM
(4096 Point FFT; f
IN
= 247kHz, 0.5dB)
0
125
25
75
100
50
Frequency (kHz)
Amplitude (dB)
2.485
2.480
2.490
2.495
2.500
2.505
2.510
2.515
2.520
30
70
90
10
30
50
10
Temperature (°C)
Reference Voltage (V)
REFERENCE VOLTAGE
vs TEMPERATURE
3.35
3.30
3.40
3.45
3.50
3.55
3.60
3.65
3.70
CONVERSION TIME (t
2
+ t
4
)
vs TEMPERATURE
30
70
90
10
30
50
10
Temperature (°C)
Conversion Time (µs)
140
120
100
80
60
40
20
0
FREQUENCY SPECTRUM
(4096 Point FFT; f
IN
= 99kHz, 0.5dB)
0
125
25
75
100
50
Frequency (kHz)
Amplitude (dB)
7FFFh
4000h
0000h
C000h
8000h
4
2
0
2
4
4
2
0
2
4
INTEGRAL LINEARITY ERROR AND
DIFFERENTIAL LINEARITY ERROR
vs OUTPUT CODE
Hex BTC Code
ILE (LSB)
DLE (LSB)
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