Texas Instruments ADS7844, ADS7844NB Datasheet
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ADS7844
SBAS100A – JANUARY 1998 – REVISED OCTOBER 2003
ADS7844
12-Bit, 8-Channel Serial Output Sampling
ANALOG-TO-DIGITAL CONVERTER
FEATURES
● SINGLE SUPPLY: 2.7V to 5V
● 8-CHANNEL SINGLE-ENDED OR
4-CHANNEL DIFFERENTIAL INPUT
● UP TO 200kHz CONVERSION RATE
● ±1 LSB MAX INL AND DNL
● NO MISSING CODES
● 72dB SINAD
● SERIAL INTERFACE
● 20-LEAD QSOP AND
20-LEAD SSOP PACKAGES
● ALTERNATE SOURCE FOR MAX147
APPLICATIONS
● DATA ACQUISITION
● TEST AND MEASUREMENT
● INDUSTRIAL PROCESS CONTROL
● PERSONAL DIGITAL ASSISTANTS
● BATTERY-POWERED SYSTEMS
DESCRIPTION
The ADS7844 is an 8-channel, 12-bit sampling analog-todigital 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
varied between 100mV and VCC, providing a corresponding
input voltage range of 0V to V
. The device includes a
REF
shutdown mode that reduces power dissipation to under
1µW. The ADS7844 is ensured down to 2.7V operation.
Low power, high speed, and onboard multiplexer make the
ADS7844 ideal for battery-operated systems such as personal
digital assistants, portable multichannel 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
equivalent 20-lead SSOP package and is ensured over the
–40°C to +85°C temperature range.
REF
) can be
CH0
CH1
CH2
CH3
CH4
CH5
CH6
CH7
COM
V
REF
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.
Eight
Channel
Multiplexer
CDAC
SAR
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Comparator
DCLK
CS
Serial
Interface
and
Control
Copyright © 1998-2003, Texas Instruments Incorporated
SHDN
DIN
DOUT
BUSY
SPECIFICATION: +5V
At TA = –40°C to +85°C, +VCC = +5V, V
PARAMETER CONDITIONS MIN TYP MAX MIN TYP MAX UNITS
ANALOG INPUT
Full-Scale Input Span Positive Input - Negative Input 0 V
Absolute Input Range Positive Input –0.2 +V
Capacitance 25 ✻ pF
Leakage Current ±1 ✻ µA
SYSTEM PERFORMANCE
Resolution 12 ✻ Bits
No Missing Codes 12 ✻ Bits
Integral Linearity Error ±2 ±1 LSB
Differential Linearity Error ±0.8 ±0.5 ±1 LSB
Offset Error ±3 ✻ LSB
Offset Error Match 0.15 1.0 ✻✻ LSB
Gain Error ±4 ±3 LSB
Gain Error Match 0.1 1.0 ✻✻ LSB
Noise 30 ✻ µVrms
Power Supply Rejection 70 ✻ dB
SAMPLING DYNAMICS
Conversion Time 12 ✻ Clk Cycles
Acquisition Time 3 ✻ Clk Cycles
Throughput Rate 200 ✻ kHz
Multiplexer Settling Time 500 ✻ ns
Aperture Delay 30 ✻ ns
Aperture Jitter 100 ✻ ps
DYNAMIC CHARACTERISTICS
Total Harmonic Distortion
(2)
Signal-to-(Noise + Distortion) V
Spurious Free Dynamic Range V
Channel-to-Channel Isolation V
REFERENCE INPUT
Range 0.1 +V
Resistance DCLK Static 5 ✻ GΩ
Input Current 45 100 ✻✻ µA
DIGITAL INPUT/OUTPUT
Logic Family CMOS ✻
Logic Levels
V
IH
V
IL
V
OH
V
OL
Data Format Straight Binary ✻
POWER SUPPLY REQUIREMENTS
+V
CC
Quiescent Current 550 900 ✻ µA
Power Dissipation 4.5 ✻ mW
TEMPERATURE RANGE
Specified Performance –40 +85 ✻✻°C
REF
= +5V, f
= 200kHz, and f
SAMPLE
CLK
= 16 • f
= 3.2MHz, unless otherwise noted.
SAMPLE
ADS7844E, N ADS7844EB, NB
REF
+0.2 ✻✻V
Negative Input –0.2 +1.25 ✻✻V
CC
✻✻V
VIN = 5VPP at 10kHz –76 –78 dB
= 5VPP at 10kHz 71 72 dB
IN
= 5VPP at 10kHz 76 78 dB
IN
= 5VPP at 50kHz 120 ✻ dB
IN
CC
f
= 12.5kHz 2.5 ✻ µA
SAMPLE
DCLK Static 0.001 3 ✻✻ µA
✻✻V
| IIH | ≤ +5µA 3.0 5.5 ✻✻V
| IIL | ≤ +5µA –0.3 +0.8 ✻✻V
IOH = –250µA 3.5 ✻ V
IOL = 250µA 0.4 ✻ V
Specified Performance 4.75 5.25 ✻✻V
f
= 12.5kHz 300 ✻ µA
SAMPLE
Power-Down Mode
(3)
, CS = +V
CC
3 ✻ µA
(1)
✻ Same specifications as ADS7844E, ADS7844N.
NOTE: (1) LSB means Least Significant Bit. With V
(PD1 = PD0 = 0) active or SHDN = GND.
2
equal to +5.0V, one LSB is 1.22mV. (2) First five harmonics of the test frequency. (3) Auto power-down mode
REF
ADS7844
www.ti.com
SBAS100A
SPECIFICATION: +2.7V
At TA = –40°C to +85°C, +VCC = +2.7V, V
PARAMETER CONDITIONS MIN TYP MAX MIN TYP MAX UNITS
ANALOG INPUT
Full-Scale Input Span Positive Input - Negative Input 0 V
Absolute Input Range Positive Input –0.2 +V
Capacitance 25 ✻ pF
Leakage Current ±1 ✻ µA
SYSTEM PERFORMANCE
Resolution 12 ✻ Bits
No Missing Codes 12 ✻ Bits
Integral Linearity Error ±2 ±1 LSB
Differential Linearity Error ±0.8 ±0.5 ±1 LSB
Offset Error ±3 ✻ LSB
Offset Error Match 0.15 1.0 ✻✻ LSB
Gain Error ±4 ±3 LSB
Gain Error Match 0.1 1.0 ✻✻ LSB
Noise 30 ✻ µVrms
Power Supply Rejection 70 ✻ dB
SAMPLING DYNAMICS
Conversion Time 12 ✻ Clk Cycles
Acquisition Time 3 ✻ Clk Cycles
Throughput Rate 125 ✻ kHz
Multiplexer Settling Time 500 ✻ ns
Aperture Delay 30 ✻ ns
Aperture Jitter 100 ✻ ps
DYNAMIC CHARACTERISTICS
Total Harmonic Distortion
(2)
Signal-to-(Noise + Distortion) V
Spurious Free Dynamic Range V
Channel-to-Channel Isolation V
REFERENCE INPUT
Range 0.1 +V
Resistance DCLK Static 5 ✻ GΩ
Input Current 13 40 ✻✻ µA
DIGITAL INPUT/OUTPUT
Logic Family CMOS ✻
Logic Levels
V
IH
V
IL
V
OH
V
OL
Data Format Straight Binary ✻
POWER SUPPLY REQUIREMENTS
+V
CC
Quiescent Current 280 650 ✻✻ µA
Power Dissipation 1.8 ✻ mW
TEMPERATURE RANGE
Specified Performance –40 +85 ✻✻°C
= +2.5V, f
REF
= 125kHz, and f
SAMPLE
CLK
= 16 • f
= 2MHz, unless otherwise noted.
SAMPLE
ADS7844E, N ADS7844EB, NB
REF
+0.2 ✻✻V
Negative Input –0.2 +0.2 ✻✻V
CC
✻✻V
VIN = 2.5VPP at 10kHz –75 –77 dB
= 2.5VPP at 10kHz 7 1 72 dB
IN
= 2.5VPP at 10kHz 7 8 80 dB
IN
= 2.5VPP at 50kHz 100 ✻ dB
IN
CC
f
= 12.5kHz 2.5 ✻ µA
SAMPLE
DCLK Static 0.001 3 ✻✻ µA
| I
| ≤ +5µA+V
IH
| I
| ≤ +5µA –0.3 +0.8 ✻✻V
IL
IOH = –250µA+V
IOL = 250µA 0.4 ✻ V
• 0.7 5.5 ✻✻V
CC
• 0.8 ✻ V
CC
✻✻V
Specified Performance 2.7 3.6 ✻✻V
f
= 12.5kHz 220 ✻ µA
SAMPLE
Power-Down Mode
(3)
, CS = +V
CC
3 ✻ µA
(1)
✻ Same specifications as ADS7844E, ADS7844N.
NOTE: (1) LSB means Least Significant Bit. With V
(PD1 = PD0 = 0) active or SHDN = GND.
ADS7844
SBAS100A
equal to +2.5V, one LSB is 610mV. (2) First five harmonics of the test frequency. (3) Auto power-down mode
REF
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3
PACKAGE/ORDERING INFORMATION
MINIMUM
RELATIVE MAXIMUM SPECIFIED
ACCURACY GAIN ERROR TEMPERATURE PACKAGE ORDERING TRANSPORT
PRODUCT (LSB) (LSB) RANGE PACKAGE-LEAD DESIGNATOR NUMBER MEDIA, QUANTITY
ADS7844E ±2 ±4 –40°C to +85°C QSOP-20 DBQ ADS7844E Rails, 56
" " " " " " ADS7844E/2K5 Tape and Reel, 2500
ADS7844N " " " SSOP-20 DB ADS7844N Rails, 68
" " " " " " ADS7844N/1K Tape and Reel,1000
ADS7844EB ±1 ±3 –40°C to +85°C QSOP-20 DBQ ADS7844EB Rails, 56
" " " " " " ADS7844EB/2K5 Tape and Reel, 2500
ADS7844NB " " " SSOP-20 DB ADS7844NB Rails, 68
" " " " " " ADS7844NB/1K Tape and Reel, 1000
NOTES: (1) For the most current package and ordering information, see the Package Option Addendum at the end of this data sheet.
(1)
PIN CONFIGURATION
Top View
CH0
1
CH1
2
CH2
3
CH3
4
CH4
CH5
CH6
CH7
COM
SHDN
5
6
7
8
9
10
ADS7844
ABSOLUTE MAXIMUM RATINGS
+V
to GND ........................................................................ –0.3V to +6V
CC
Analog Inputs to GND ............................................ –0.3V to +V
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.
+V
20
CC
19
D
CLK
18
CS
17
D
IN
16
BUSY
15
D
OUT
14
GND
13
GND
12
+V
CC
11
V
REF
(1)
+ 0.3V
CC
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
10 SHDN Shutdown. When LOW, the device enters a very low
11 V
12 +V
13 GND Ground
14 GND Ground
15 D
16 BUSY Busy Output. Busy goes low when the DIN control bits
17 D
18 CS Chip Select Input. Active LOW. Data will not be clocked
19 CLK External Clock Input. The clock speed determines the
20 +V
Ground reference for analog inputs. Sets zero code
voltage in single ended mode. Connect this pin to ground
or ground reference point.
power shutdown mode.
Voltage Reference Input. See Specification Table for
REF
ranges.
Power Supply, 2.7V to 5V.
CC
Serial Data Output. Data is shifted on the falling edge of
OUT
D
. This output is high impedance when
CLK
CS is high.
are being read and also when the device is converting.
The Output is high impedance when CS is High.
Serial Data Input. If CS is LOW, data is latched on rising
IN
edge of D
into D
impedance.
conversion rate by the equation f
Power Supply
CC
.
CLK
unless CS is low. When CS is high D
IN
= 16 • f
CLK
OUT
SAMPLE
ELECTROSTATIC
is high
.
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 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.
4
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ADS7844
SBAS100A
TYPICAL PERFORMANCE CURVES:+5V
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
fIN = 10kHz, –0.2dB
At TA = +25°C, +VCC = +5V, V
= +5V, f
REF
= 200kHz, and f
SAMPLE
CLK
= 16 • f
= 3.2MHz, unless otherwise noted.
SAMPLE
(4096 Point FFT; fIN = 1,123Hz, –0.2dB)
0
–20
–40
–60
–80
Amplitude (dB)
–100
–120
0 10025 7550
SIGNAL-TO-NOISE RATIO AND SIGNAL-TO-
74
73
72
71
70
SNR and SINAD (dB)
69
(NOISE+DISTORTION) vs INPUT FREQUENCY
SINAD
FREQUENCY SPECTRUM
Frequency (kHz)
SNR
(4096 Point FFT; fIN = 10.3kHz, –0.2dB)
0
–20
–40
–60
–80
Amplitude (dB)
–100
–120
0 10025 7550
SPURIOUS FREE DYNAMIC RANGE AND TOTAL
HARMONIC DISTORTION vs INPUT FREQUENCY
85
80
75
SFDR (dB)
70
FREQUENCY SPECTRUM
Frequency (kHz)
SFDR
THD
–85
–80
–75
THD (dB)
–70
68
Input Frequency (kHz)
EFFECTIVE NUMBER OF BITS
12.0
11.8
11.6
11.4
Effective Number of Bits
11.2
11.0
ADS7844
SBAS100A
vs INPUT FREQUENCY
Input Frequency (kHz)
101 100
101 100
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65
101 100
Input Frequency (kHz)
–65
5
TYPICAL PERFORMANCE CURVES:+2.7V
At TA = +25°C, +VCC = +2.7V, V
= +2.5V, f
REF
= 125kHz, and f
SAMPLE
CLK
= 16 • f
= 2MHz, unless otherwise noted.
SAMPLE
(4096 Point FFT; fIN = 1,129Hz, –0.2dB)
0
–20
–40
–60
–80
Amplitude (dB)
–100
–120
0 62.515.6 46.931.3
SIGNAL-TO-NOISE RATIO AND SIGNAL-TO-
(NOISE+DISTORTION) vs INPUT FREQUENCY
78
74
70
66
62
SNR and SINAD (dB)
58
54
FREQUENCY SPECTRUM
Frequency (kHz)
SNR
SINAD
101 100
Input Frequency (kHz)
(4096 Point FFT; fIN = 10.6kHz, –0.2dB)
0
–20
–40
–60
–80
Amplitude (dB)
–100
–120
0 62.515.6 46.931.3
SPURIOUS FREE DYNAMIC RANGE AND TOTAL
HARMONIC DISTORTION vs INPUT FREQUENCY
90
85
80
75
70
65
SFDR (dB)
60
55
50
FREQUENCY SPECTRUM
Frequency (kHz)
SFDR
THD
101 100
Input Frequency (kHz)
–90
–85
–80
–75
–70
–65
–60
–55
–50
THD (dB)
12.0
11.5
11.0
10.5
10.0
Effective Number of Bits
9.5
9.0
6
EFFECTIVE NUMBER OF BITS
vs INPUT FREQUENCY
101 100
Input Frequency (kHz)
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0.4
0.2
0.0
–0.2
–0.4
Delta from +25°C (dB)
–0.6
–0.8
CHANGE IN SIGNAL-TO-(NOISE+DISTORTION)
fIN = 10kHz, –0.2dB
–20–40 100
vs TEMPERATURE
0 20 40 60 80
Temperature (˚C)
ADS7844
SBAS100A
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