ADS1254
ADS
125
4
SBAS213 – JUNE 2001
24-Bit, 20kHz, Low Power
ANALOG-TO-DIGITAL CONVERTER
FEATURES
q
24 BITS—NO MISSING CODES
q
19 BITS EFFECTIVE RESOLUTION UP TO
20kHz DATA RATE
q
LOW NOISE: 1.8ppm
q
FOUR DIFFERENTIAL INPUTS
q
INL: 15ppm (max)
q
EXTERNAL REFERENCE (0.5V to 5V)
q
POWER-DOWN MODE
q
SYNC MODE
q
LOW POWER: 4mW at 20kHz
q
SEPARATE DIGITAL INTERFACE SUPPLY 1.8V
to 3.6V
DESCRIPTION
The ADS1254 is a precision, wide dynamic range, delta-
sigma, Analog-to-Digital (A/D) converter with 24-bit reso-
lution. The delta-sigma architecture is used for wide dy-
namic range and to ensure 24 bits of no missing codes
performance. An effective resolution of 19 bits (1.8ppm of
rms noise) is achieved for conversion rates up to 20kHz.
The ADS1254 is designed for high-resolution measurement
applications in cardiac diagnostics, smart transmitters, in-
dustrial process control, weight scales, chromatography, and
portable instrumentation. The converter includes a flexible,
two-wire synchronous serial interface for low-cost isolation.
The ADS1254 is a multi-channel converter and is offered in
an SSOP-20 package.
APPLICATIONS
q
q
q
q
q
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CARDIAC DIAGNOSTICS
DIRECT THERMOCOUPLE INTERFACES
BLOOD ANALYSIS
INFRARED PYROMETERS
LIQUID/GAS CHROMATOGRAPHY
PRECISION PROCESS CONTROL
ADS1254
CH1+
CH1–
CH2+
CH2–
Mux
CH3+
CH3–
CH4+
CH4–
Control
4th-Order
∆Σ
Modulator
Digital
Filter
Serial
Interface
SCLK
DOUT/DRDY
AV
DD
AGND
DV
DD
DGND
V
REF
CLK
CHSEL0 CHSEL1
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.
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 © 2001, Texas Instruments Incorporated
www.ti.com
ABSOLUTE MAXIMUM RATINGS
Analog Input: Current (Momentary) ..............................................
±100mA
(Continuous) ...............................................
±10mA
Voltage ................................... GND – 0.3V to V
DD
+ 0.3V
AV
DD
to AGND ....................................................................... –0.3V to 6V
DV
DD
to AV
DD
.......................................................................... –6V to +6V
DV
DD
to DGND ....................................................................... –0.3V to 6V
V
REF
Voltage to AGND ............................................. –0.3V to V
DD
+ 0.3V
Digital Input Voltage to DGND ................................. –0.3V to V
DD
+ 0.3V
Digital Output Voltage to DGND .............................. –0.3V to V
DD
+ 0.3V
Lead Temperature (soldering, 10s) .............................................. +300°C
Power Dissipation (any package) ................................................. 500mW
ELECTROSTATIC
DISCHARGE SENSITIVITY
This integrated circuit can be damaged by ESD. Texas Instru-
ments 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/ORDERING INFORMATION
PACKAGE
DRAWING
NUMBER
349
SPECIFIED
TEMPERATURE
RANGE
–40°C to +85°C
PACKAGE
MARKING
ADS1254E
ORDERING
NUMBER
(1)
ADS1254E
ADS1254E/2K5
TRANSPORT
MEDIA
Rails
Tape and Reel
PRODUCT
ADS1254E
PACKAGE
SSOP-20
"
"
"
"
"
NOTE: (1) 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 “ADS1254E/2K5” will get a single 2500-piece Tape and Reel.
ELECTRICAL CHARACTERISTICS
All specifications at T
MIN
to T
MAX
, AV
DD
= +5V, DV
DD
= +1.8V. CLK = 8MHz, and V
REF
= 4.096, unless otherwise specified.
ADS1254E
PARAMETER
ANALOG INPUT
Input Voltage Range
Input Impedance
CONDITIONS
MIN
AGND
CLK = 3,840Hz
CLK = 1MHz
CLK = 8MHz
At +25°C
At T
MIN
to T
MAX
260
1
125
6
5
TYP
MAX
±V
REF
UNITS
V
MΩ
MΩ
kΩ
pF
pA
nA
kHz
kHz
MHz
MHz
% of FSR
dB
ppm of FSR, rms
Bits
Bits
dB
% of FSR
ppm of FSR
dB
ppm/°C
ppm/°C
V
DD
V
µA
Input Capacitance
Input Leakage
DYNAMIC CHARACTERISTICS
Data Rate
Bandwidth
Serial Clock (SCLK)
System Clock Input (CLK)
ACCURACY
Integral Non-Linearity
(1)
THD
Noise
Resolution
No Missing Codes
Common-Mode Rejection
Gain Error
Offset Error
Gain Sensitivity to V
REF
Power-Supply Rejection Ratio
PERFORMANCE OVER TEMPERATURE
Offset Drift
Gain Drift
VOLTAGE REFERENCE
V
REF
Load Current
NOTE: (1) Applies to full-differential signals.
50
1
20.8
–3dB
4.24
8
8
±0.0002
105
1.8
24
24
102
0.1
±30
1:1
88
0.07
0.4
0.5
4.096
32
±0.0015
2.7
1kHz Input; 0.1dB below FS
60Hz, AC
90
1
±100
70
2
ADS1254
SBAS213
ELECTRICAL CHARACTERISTICS
(Cont.)
All specifications at T
MIN
to T
MAX
, AV
DD
= +5V, DV
DD
= +1.8V. CLK = 8MHz, and V
REF
= 4.096, unless otherwise specified.
ADS1254E
PARAMETER
DIGITAL INPUT/OUTPUT
Logic Family
Logic Level: V
IH
V
IL
V
OH
V
OL
Input (SCLK, CLK, CHSEL0, CHSEL1) Hysteresis
Data Format
POWER-SUPPLY REQUIREMENTS
Power Supply Voltage
Quiescent Current
Operating Power
Power-Down Current
TEMPERATURE RANGE
Operating
Storage
–40
–60
CONDITIONS
MIN
TYP
MAX
UNITS
CMOS
0.65 • DV
DD
–0.3
DV
DD
–0.4
DV
DD
+ 0.3
0.35 • DV
DD
0.4
0.6
Offset Binary Two’s Complement
DV
DD
AV
DD
AV
DD
= +5V
DV
DD
= +1.8V
1.8
4.75
3.6
5.25
1.15
0.4
6.5
1
+85
+100
V
V
V
V
V
I
OH
= –500µA
I
OL
= 500µA
5
0.8
0.2
4.3
0.4
VDC
VDC
mA
mA
mW
µA
°C
°C
PIN CONFIGURATION
Top View
SSOP-20
PIN DESCRIPTIONS
PIN
1
2
3
4
5
NAME
CH1+
CH1–
CH2+
CH2–
CH3+
CH3–
AV
DD
CLK
PIN DESCRIPTION
Analog Input: Positive Input of the Differen-
tial Analog Input
Analog Input: Negative Input of the Differ-
ential Analog Input
Analog Input: Positive Input of the Differen-
tial Analog Input
Analog Input: Negative Input of the Differ-
ential Analog Input
Analog Input: Positive Input of the Differen-
tial Analog Input
Analog Input: Negative Input of the Differ-
ential Analog Input
Input: Analog Power Supply Voltage, +5V
Digital Input: Device System Clock. The
system clock is in the form of a CMOS-
compatible clock. This is a Schmitt-Trigger
input
Input: Digital Power Supply Voltage
No Connection
No Connection
Input: Digital Ground
Digital Output: Serial Data Output/Data
Ready. This output indicates that a new
output word is available from the ADS1254
data output register. The serial data is
clocked out of the serial data output shift
register using SCLK.
Digital Input: Serial Clock. The serial clock
is in the form of a CMOS-compatible clock.
The serial clock operates independently
from the system clock, therefore, it is pos-
sible to run SCLK at a higher frequency
than CLK. The normal state of SCLK is
LOW. Holding SCLK HIGH will either ini-
tiate a modulator reset for synchronizing
multiple converters or enter power-down
mode. This is a Schmitt-Trigger input.
Digital Input: Used to select analog input
channel. This is a Schmitt-Trigger Input
Digital Input: Used to select analog input
channel. This is a Schmitt-Trigger Input
Input: Analog Ground
Analog Input: Reference Voltage Input
Analog Input: Negative Input of the Differ-
ential Analog Input
Analog Input: Positive Input of the Differen-
tial Analog Input
CH1+
CH1–
CH2+
CH2–
CH3+
CH3–
AV
DD
CLK
1
2
3
4
5
6
7
8
20
19
CH4+
CH4–
6
7
8
18 V
REF
17 AGND
16
15
CHSEL0
CHSEL1
ADS1254E
9
10
11
12
13
DV
DD
NC
NC
DGND
DOUT/DRDY
14 SCLK
14
13 DOUT/DRDY
12 DGND
11 NC
SCLK
DV
DD
9
NC
10
15
16
17
18
19
20
CHSEL1
CHSEL0
AGND
V
REF
CH4–
CH4+
ADS1254
SBAS213
3
TYPICAL CHARACTERISTICS
At T
A
= +25°C, AV
DD
= +5V, DV
DD
= +1.8V, CLK = 8MHz, and V
REF
= 4.096, unless otherwise specified.
RMS NOISE vs DATA OUTPUT RATE
2.0
1.9
20.0
19.8
EFFECTIVE RESOLUTION vs DATA OUTPUT RATE
RMS Noise (ppm of FS)
1.7
1.6
1.5
1.4
1.3
1.2
1.1
1.0
100
1k
10k
100k
Data Ouput Rate (Hz)
Effective Resolution (Bits)
1.8
19.6
19.4
19.2
19.0
18.8
18.6
18.4
18.2
18.0
100
1k
10k
100k
Data Ouput Rate (Hz)
RMS NOISE vs TEMPERATURE
2.0
1.8
20
19.8
EFFECTIVE RESOLUTION vs TEMPERATURE
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
–40
–20
0
20
40
60
80
100
Temperature (°C)
Effective Resolution (Bits)
RMS Noise (ppm of FS)
1.6
19.6
19.4
19.2
19.0
18.8
18.6
18.4
18.2
18.0
–40
–20
0
20
40
60
80
100
Temperature (°C)
RMS NOISE vs V
REF
Voltage
10
9
RMS Noise (ppm of FS)
RMS NOISE vs V
REF
Voltage
12
10
8
6
4
2
0
8
RMS Noise (µV)
7
6
5
4
3
2
1
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
V
REF
Voltage (V)
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5
V
REF
Voltage (V)
4
ADS1254
SBAS213
TYPICAL CHARACTERISTICS
(Cont.)
At T
A
= +25°C, AV
DD
= +5V, DV
DD
= +1.8V, CLK = 8MHz, and V
REF
= 4.096, unless otherwise specified.
RMS NOISE vs INPUT VOLTAGE
2
INTEGRAL NONLINEARITY vs TEMPERATURE
2.5
RMS Noise (ppm of FS)
1.5
2.0
INL (ppm of FS)
–5
–4
–3
–2
–1
0
1
2
3
4
5
1.5
1
1.0
0.5
0.5
0
Input Voltage (V)
0
–40
–20
0
20
40
60
80
100
Temperature (°C)
INTEGRAL NON-LINEARITY vs DATA OUTPUT RATE
6
5
DC Offset (ppm of FS)
OFFSET vs TEMPERATURE
20
18
16
14
12
10
8
6
4
2
0
–40
–20
0
20
40
60
80
100
INL (ppm of FS)
4
3
2
1
0
100
1k
10k
100k
Data Output Rate (Hz)
Temperature (°C)
GAIN ERROR vs TEMPERATURE
600
580
Gain Error (ppm of FS)
PSR vs CLK FREQUENCY
–0
–10
–20
–30
560
540
520
500
480
–60
–40
–20
0
20
40
60
80
100
Temperature (°C)
PSR (dB)
–40
–50
–60
–70
–80
–90
–100
1
2
3
4
5
6
7
8
Clock Frequency (MHz)
ADS1254
SBAS213
5
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