ADS7844
12-Bit, 8-Channel Serial Output Sampling
ANALOG-TO-DIGITAL CONVERTER
FEATURES
q
SINGLE SUPPLY: 2.7V to 5V
q
8-CHANNEL SINGLE-ENDED OR
4-CHANNEL DIFFERENTIAL INPUT
q
UP TO 200kHz CONVERSION RATE
q
±
1 LSB MAX INL AND DNL
q
GUARANTEED NO MISSING CODES
q
72dB SINAD
q
SERIAL INTERFACE
q
20-LEAD QSOP AND
20-LEAD SSOP PACKAGES
q
ALTERNATE SOURCE FOR MAX147
®
DESCRIPTION
The ADS7844 is an 8-channel, 12-bit sampling ana-
log-to-digital converter (ADC) with a synchronous
serial interface. Typical power dissipation is 3mW at
a 200kHz throughput rate and a +5V supply. The
reference voltage (V
REF
) can be varied between 100mV
and V
CC
, providing a corresponding input voltage
range of 0V to V
REF
. The device includes a shutdown
mode which reduces power dissipation to under 1
µ
W.
The ADS7844 is guaranteed down to 2.7V operation.
Low power, high speed, and on-board multiplexer
make the ADS7844 ideal for battery operated systems
such as personal digital assistants, portable multi-
channel data loggers, and measurement equipment.
The serial interface also provides low-cost isolation
for remote data acquisition. The ADS7844 is available
in a 20-lead QSOP package and the MAX147 equiva-
lent 20-lead SSOP package and is guaranteed over the
–40
°
C to +85
°
C temperature range.
©
1998 Burr-Brown Corporation
PDS-1463D
Printed in U.S.A. July, 1999
APPLICATIONS
q
DATA ACQUISITION
q
TEST AND MEASUREMENT
q
INDUSTRIAL PROCESS CONTROL
q
PERSONAL DIGITAL ASSISTANTS
q
BATTERY-POWERED SYSTEMS
CDAC
SAR
Comparator
Eight
Channel
Multiplexer
Serial
Interface
and
Control
CH4
CH5
CH6
CH7
COM
V
REF
CH0
CH1
CH2
CH3
CS
SHDN
DIN
DOUT
BUSY
DCLK
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
ADS7844
ADS
7844
®
2
ADS7844
SPECIFICATION: +5V
At T
A
= –40
°
C to +85
°
C, +V
CC
= +5V, V
REF
= +5V, f
SAMPLE
= 200kHz, and f
CLK
= 16 • f
SAMPLE
= 3.2MHz, unless otherwise noted.
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.
ADS7844E, N
ADS7844EB, NB
PARAMETER
CONDITIONS
MIN
TYP
MAX
MIN
TYP
MAX
UNITS
ANALOG INPUT
Full-Scale Input Span
Positive Input - Negative Input
0
V
REF
T
T
V
Absolute Input Range
Positive Input
–0.2
+V
CC
+0.2
T
T
V
Negative Input
–0.2
+1.25
T
T
V
Capacitance
25
T
pF
Leakage Current
±
1
T
µ
A
SYSTEM PERFORMANCE
Resolution
12
T
Bits
No Missing Codes
12
T
Bits
Integral Linearity Error
±
2
±
1
LSB
(1)
Differential Linearity Error
±
0.8
±
0.5
±
1
LSB
Offset Error
±
3
T
LSB
Offset Error Match
0.15
1.0
T
T
LSB
Gain Error
±
4
±
3
LSB
Gain Error Match
0.1
1.0
T
T
LSB
Noise
30
T
µ
Vrms
Power Supply Rejection
70
T
dB
SAMPLING DYNAMICS
Conversion Time
12
T
Clk Cycles
Acquisition Time
3
T
Clk Cycles
Throughput Rate
200
T
kHz
Multiplexer Settling Time
500
T
ns
Aperture Delay
30
T
ns
Aperture Jitter
100
T
ps
DYNAMIC CHARACTERISTICS
Total Harmonic Distortion
(2)
V
IN
= 5Vp-p at 10kHz
–76
–78
dB
Signal-to-(Noise + Distortion)
V
IN
= 5Vp-p at 10kHz
71
72
dB
Spurious Free Dynamic Range
V
IN
= 5Vp-p at 10kHz
76
78
dB
Channel-to-Channel Isolation
V
IN
= 5Vp-p at 50kHz
120
T
dB
REFERENCE INPUT
Range
0.1
+V
CC
T
T
V
Resistance
DCLK Static
5
T
G
Ω
Input Current
45
100
T
T
µ
A
f
SAMPLE
= 12.5kHz
2.5
T
µ
A
DCLK Static
0.001
3
T
T
µ
A
DIGITAL INPUT/OUTPUT
Logic Family
CMOS
T
Logic Levels
V
IH
| I
IH
|
≤
+5
µ
A
3.0
5.5
T
T
V
V
IL
| I
IL
|
≤
+5
µ
A
–0.3
+0.8
T
T
V
V
OH
I
OH
= –250
µ
A
3.5
T
V
V
OL
I
OL
= 250
µ
A
0.4
T
V
Data Format
Straight Binary
T
POWER SUPPLY REQUIREMENTS
+V
CC
Specified Performance
4.75
5.25
T
T
V
Quiescent Current
550
900
T
µ
A
f
SAMPLE
= 12.5kHz
300
T
µ
A
Power-Down Mode
(3)
, CS = +V
CC
3
T
µ
A
Power Dissipation
4.5
T
mW
TEMPERATURE RANGE
Specified Performance
–40
+85
T
T
°
C
T
Same specifications as ADS7844E, ADS7844N.
NOTE: (1) LSB means Least Significant Bit. With V
REF
equal to +5.0V, one LSB is 1.22mV. (2) First five harmonics of the test frequency. (3) Auto power-down mode
(PD1 = PD0 = 0) active or SHDN = GND.
®
3
ADS7844
SPECIFICATION: +2.7V
At T
A
= –40
°
C to +85
°
C, +V
CC
= +2.7V, V
REF
= +2.5V, f
SAMPLE
= 125kHz, and f
CLK
= 16 • f
SAMPLE
= 2MHz, unless otherwise noted.
ADS7844E, N
ADS7844EB, NB
PARAMETER
CONDITIONS
MIN
TYP
MAX
MIN
TYP
MAX
UNITS
ANALOG INPUT
Full-Scale Input Span
Positive Input - Negative Input
0
V
REF
T
T
V
Absolute Input Range
Positive Input
–0.2
+V
CC
+0.2
T
T
V
Negative Input
–0.2
+0.2
T
T
V
Capacitance
25
T
pF
Leakage Current
±
1
T
µ
A
SYSTEM PERFORMANCE
Resolution
12
T
Bits
No Missing Codes
12
T
Bits
Integral Linearity Error
±
2
±
1
LSB
(1)
Differential Linearity Error
±
0.8
±
0.5
±
1
LSB
Offset Error
±
3
T
LSB
Offset Error Match
0.15
1.0
T
T
LSB
Gain Error
±
4
±
3
LSB
Gain Error Match
0.1
1.0
T
T
LSB
Noise
30
T
µ
Vrms
Power Supply Rejection
70
T
dB
SAMPLING DYNAMICS
Conversion Time
12
T
Clk Cycles
Acquisition Time
3
T
Clk Cycles
Throughput Rate
125
T
kHz
Multiplexer Settling Time
500
T
ns
Aperture Delay
30
T
ns
Aperture Jitter
100
T
ps
DYNAMIC CHARACTERISTICS
Total Harmonic Distortion
(2)
V
IN
= 2.5Vp-p at 10kHz
–75
–77
dB
Signal-to-(Noise + Distortion)
V
IN
= 2.5Vp-p at 10kHz
71
72
dB
Spurious Free Dynamic Range
V
IN
= 2.5Vp-p at 10kHz
78
80
dB
Channel-to-Channel Isolation
V
IN
= 2.5Vp-p at 50kHz
100
T
dB
REFERENCE INPUT
Range
0.1
+V
CC
T
T
V
Resistance
DCLK Static
5
T
G
Ω
Input Current
13
40
T
T
µ
A
f
SAMPLE
= 12.5kHz
2.5
T
µ
A
DCLK Static
0.001
3
T
T
µ
A
DIGITAL INPUT/OUTPUT
Logic Family
CMOS
T
Logic Levels
V
IH
| I
IH
|
≤
+5
µ
A
+V
CC
• 0.7
5.5
T
T
V
V
IL
| I
IL
|
≤
+5
µ
A
–0.3
+0.8
T
T
V
V
OH
I
OH
= –250
µ
A
+V
CC
• 0.8
T
V
V
OL
I
OL
= 250
µ
A
0.4
T
V
Data Format
Straight Binary
T
POWER SUPPLY REQUIREMENTS
+V
CC
Specified Performance
2.7
3.6
T
T
V
Quiescent Current
280
650
T
T
µ
A
f
SAMPLE
= 12.5kHz
220
T
µ
A
Power-Down Mode
(3)
, CS = +V
CC
3
T
µ
A
Power Dissipation
1.8
T
mW
TEMPERATURE RANGE
Specified Performance
–40
+85
T
T
°
C
T
Same specifications as ADS7844E, ADS7844N.
NOTE: (1) LSB means Least Significant Bit. With V
REF
equal to +2.5V, one LSB is 610mV. (2) First five harmonics of the test frequency. (3) Auto power-down mode
(PD1 = PD0 = 0) active or SHDN = GND.
®
4
ADS7844
PIN CONFIGURATION
Top View
PIN DESCRIPTIONS
PIN
NAME
DESCRIPTION
1
CH0
Analog Input Channel 0.
2
CH1
Analog Input Channel 1.
3
CH2
Analog Input Channel 2.
4
CH3
Analog Input Channel 3.
5
CH4
Analog Input Channel 4.
6
CH5
Analog Input Channel 5.
7
CH6
Analog Input Channel 6.
8
CH7
Analog Input Channel 7.
9
COM
Ground reference for analog inputs. Sets zero code
voltage in single ended mode. Connect this pin to ground
or ground reference point.
10
SHDN
Shutdown. When LOW, the device enters a very low
power shutdown mode.
11
V
REF
Voltage Reference Input. See Specification Table for
ranges.
12
+V
CC
Power Supply, 2.7V to 5V.
13
GND
Ground
14
GND
Ground
15
D
OUT
Serial Data Output. Data is shifted on the falling edge of
D
CLK
. This output is high impedance when
CS is high.
16
BUSY
Busy Output. Busy goes low when the DIN control bits
are being read and also when the device is converting.
The Output is high impedance when CS is High.
17
D
IN
Serial Data Input. If CS is LOW, data is latched on rising
edge of D
CLK
.
18
CS
Chip Select Input. Active LOW. Data will not be clocked
into D
IN
unless CS is low. When CS is high D
OUT
is high
impedance.
19
CLK
External Clock Input. The clock speed determines the
conversion rate by the equation f
CLK
= 16 • f
SAMPLE
.
20
+V
CC
Power Supply
1
2
3
4
5
6
7
8
9
10
CH0
CH1
CH2
CH3
CH4
CH5
CH6
CH7
COM
SHDN
+V
CC
D
CLK
CS
D
IN
BUSY
D
OUT
GND
GND
+V
CC
V
REF
20
19
18
17
16
15
14
13
12
11
ADS7844
MINIMUM
RELATIVE
MAXIMUM
SPECIFICATION
PACKAGE
ACCURACY
GAIN ERROR
TEMPERATURE
DRAWING
ORDERING
TRANSPORT
PRODUCT
(LSB)
(LSB)
RANGE
PACKAGE
NUMBER
(1)
NUMBER
(2)
MEDIA
ADS7844E
±
2
±
4
–40
°
C to +85
°
C
20-Lead QSOP
349
ADS7844E
Rails
"
"
"
"
"
"
ADS7844E/2K5
Tape and Reel
ADS7844N
"
"
"
20-Lead SSOP
334
ADS7844N
Rails
"
"
"
"
"
"
ADS7844N/1K
Tape and Reel
ADS7844EB
±
1
±
3
–40
°
C to +85
°
C
20-Lead QSOP
349
ADS7844EB
Rails
"
"
"
"
"
"
ADS7844EB/2K5
Tape and Reel
ADS7844NB
"
"
"
20-Lead SSOP
334
ADS7844NB
Rails
"
"
"
"
"
"
ADS7844NB/1K
Tape and Reel
NOTES: (1) For detailed drawing and dimension table, please see end of data sheet, or Appendix C of Burr-Brown IC Data Book. (2) Models with a slash (/) are
available only in Tape and Reel in the quantities indicated (e.g., /2K5 indicates 2500 devices per reel). Ordering 2500 pieces of “ADS7844/2K5” will get a single
2500-piece Tape and Reel. For detailed Tape and Reel mechanical information, refer to Appendix B of Burr-Brown IC Data Book.
PACKAGE/ORDERING INFORMATION
ABSOLUTE MAXIMUM RATINGS
(1)
+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 +6V
Power Dissipation .......................................................................... 250mW
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
conditions for extended periods may affect device reliability.
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 specifi-
cations.
®
5
ADS7844
TYPICAL PERFORMANCE CURVES:+5V
At T
A
= +25
°
C, +V
CC
= +5V, V
REF
= +5V, f
SAMPLE
= 200kHz, and f
CLK
= 16 • f
SAMPLE
= 3.2MHz, unless otherwise noted.
0
–20
–40
–60
–80
–100
–120
FREQUENCY SPECTRUM
(4096 Point FFT; fIN = 1,123Hz, –0.2dB)
0
100
25
75
50
Frequency (kHz)
Amplitude (dB)
0
–20
–40
–60
–80
–100
–120
FREQUENCY SPECTRUM
(4096 Point FFT; fIN = 10.3kHz, –0.2dB)
0
100
25
75
50
Frequency (kHz)
Amplitude (dB)
SIGNAL-TO-NOISE RATIO AND SIGNAL-TO-
(NOISE+DISTORTION) vs INPUT FREQUENCY
10
1
100
Input Frequency (kHz)
SNR and SINAD (dB)
74
73
72
71
70
69
68
SINAD
SNR
SPURIOUS FREE DYNAMIC RANGE AND TOTAL
HARMONIC DISTORTION vs INPUT FREQUENCY
10
1
100
Input Frequency (kHz)
SFDR (dB)
THD (dB)
85
80
75
70
65
–85
–80
–75
–70
–65
THD
SFDR
12.0
11.8
11.6
11.4
11.2
11.0
EFFECTIVE NUMBER OF BITS
vs INPUT FREQUENCY
10
1
100
Input Frequency (kHz)
Effective Number of Bits
CHANGE IN SIGNAL-TO-(NOISE+DISTORTION)
vs TEMPERATURE
–20
–40
100
Temperature (°C)
Delta from +25°C (dB)
0.4
0.2
0.0
–0.2
–0.4
–0.6
0.6
0
20
40
60
80
f
IN
= 10kHz, –0.2dB
®
6
ADS7844
0
–20
–40
–60
–80
–100
–120
FREQUENCY SPECTRUM
(4096 Point FFT; fIN = 1,129Hz, –0.2dB)
0
62.5
15.6
46.9
31.3
Frequency (kHz)
Amplitude (dB)
0
–20
–40
–60
–80
–100
–120
FREQUENCY SPECTRUM
(4096 Point FFT; fIN = 10.6kHz, –0.2dB)
0
62.5
15.6
46.9
31.3
Frequency (kHz)
Amplitude (dB)
SIGNAL-TO-NOISE RATIO AND SIGNAL-TO-
(NOISE+DISTORTION) vs INPUT FREQUENCY
10
1
100
Input Frequency (kHz)
SNR and SINAD (dB)
78
74
70
66
62
58
54
SINAD
SNR
THD
SFDR
SPURIOUS FREE DYNAMIC RANGE AND TOTAL
HARMONIC DISTORTION vs INPUT FREQUENCY
10
1
100
Input Frequency (kHz)
SFDR (dB)
THD (dB)
90
85
80
75
70
65
60
55
50
–90
–85
–80
–75