TEXAS INSTRUMENTS ADS1254 Technical data

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ADS1254

ADS1254

SBAS213 – JUNE 2001

24-Bit, 20kHz, Low Power

ANALOG-TO-DIGITAL CONVERTER

FEATURES

● 24 BITS—NO MISSING CODES

● 19 BITS EFFECTIVE RESOLUTION UP TO

20kHz DATA RATE

● LOW NOISE: 1.8ppm

● FOUR DIFFERENTIAL INPUTS

● INL: 15ppm (max)

● EXTERNAL REFERENCE (0.5V to 5V)

● POWER-DOWN MODE

● SYNC MODE

● LOW POWER: 4mW at 20kHz

● SEPARATE DIGITAL INTERFACE SUPPLY 1.8V

to 3.6V

APPLICATIONS

● CARDIAC DIAGNOSTICS

● DIRECT THERMOCOUPLE INTERFACES

● BLOOD ANALYSIS

● INFRARED PYROMETERS

● LIQUID/GAS CHROMATOGRAPHY

● PRECISION PROCESS CONTROL

DESCRIPTION

The ADS1254 is a precision, wide dynamic range, delta­sigma, Analog-to-Digital (A/D) converter with 24-bit reso­lution. The delta-sigma architecture is used for wide dy­namic 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, in­dustrial 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.

ADS1254

CH1+
CH1–
CH2+
CH2–
CH3+
CH3–

CH4+
CH4–

CHSEL0

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.

Mux

CHSEL1

4th-Order

∆Σ

Modulator

www.ti.com

Digital

Filter

V

REF

CLK

Serial

Interface

Control

Copyright © 2001, Texas Instruments Incorporated

SCLK
DOUT/DRDY

AV

DD

AGND
DV

DD

DGND

ABSOLUTE MAXIMUM RATINGS

Analog Input: Current (Momentary) .............................................. ±100mA

(Continuous) ............................................... ±10mA

Voltage ................................... GND – 0.3V to V

to AGND ....................................................................... –0.3V to 6V

AV

DD

to AVDD.......................................................................... –6V to +6V

DV

DD

to DGND .......................................................................–0.3V to 6V

DV

DD

Voltage to AGND ............................................. –0.3V to VDD + 0.3V

V

REF

Digital Input Voltage to DGND ................................. –0.3V to V

Digital Output Voltage to DGND .............................. –0.3V to V

Lead Temperature (soldering, 10s).............................................. +300°C

Power Dissipation (any package) ................................................. 500mW

+ 0.3V

DD

+ 0.3V

DD

+ 0.3V

DD

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

ELECTROSTATIC
DISCHARGE SENSITIVITY

changes could cause the device not to meet its published
specifications.

PACKAGE/ORDERING INFORMATION

PACKAGE SPECIFIED

PRODUCT PACKAGE NUMBER RANGE MARKING NUMBER

DRAWING TEMPERATURE PACKAGE ORDERING TRANSPORT

ADS1254E SSOP-20 349 –40°C to +85°C ADS1254E ADS1254E Rails

(1)

MEDIA

"""""ADS1254E/2K5 Tape and Reel

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

PARAMETER CONDITIONS MIN TYP MAX UNITS
ANALOG INPUT

Input Voltage Range AGND ±V
Input Impedance CLK = 3,840Hz 260 MΩ

Input Capacitance 6pF
Input Leakage At +25°C550pA

DYNAMIC CHARACTERISTICS

Data Rate 20.8 kHz
Bandwidth –3dB 4.24 kHz
Serial Clock (SCLK) 8MHz
System Clock Input (CLK) 8MHz

ACCURACY

Integral Non-Linearity
THD 1kHz Input; 0.1dB below FS 105 dB
Noise 1.8 2.7 ppm of FSR, rms
Resolution 24 Bits
No Missing Codes 24 Bits
Common-Mode Rejection 60Hz, AC 90 102 dB
Gain Error 0.1 1 % of FSR
Offset Error ±30 ±100 ppm of FSR
Gain Sensitivity to V
Power-Supply Rejection Ratio 70 88 dB

PERFORMANCE OVER TEMPERATURE

Offset Drift 0.07 ppm/°C
Gain Drift 0.4 ppm/°C

VOLTAGE REFERENCE

V

REF

Load Current 32 µA

NOTE: (1) Applies to full-differential signals.

MIN

REF

to T

, AVDD = +5V, DVDD = +1.8V. CLK = 8MHz, and V

MAX

CLK = 1MHz 1 MΩ
CLK = 8MHz 125 kΩ

At T

(1)

MIN

to T

MAX

= 4.096, unless otherwise specified.

REF

ADS1254E

±0.0002 ±0.0015 % of FSR

1:1

0.5 4.096 V

REF

1nA

DD

V

V

2

ADS1254

SBAS213

ELECTRICAL CHARACTERISTICS (Cont.)

All specifications at T

PARAMETER CONDITIONS MIN TYP MAX UNITS

DIGITAL INPUT/OUTPUT

Logic Family CMOS
Logic Level: V

V
V

V
Input (SCLK, CLK, CHSEL0, CHSEL1) Hysteresis 0.6 V
Data Format

POWER-SUPPLY REQUIREMENTS

Power Supply Voltage DV

Quiescent Current AV

Operating Power 4.3 6.5 mW
Power-Down Current 0.4 1 µA

TEMPERATURE RANGE

Operating –40 +85 °C
Storage –60 +100 °C

to T

MIN

, AVDD = +5V, DVDD = +1.8V. CLK = 8MHz, and V

MAX

= 4.096, unless otherwise specified.

REF

ADS1254E

IH
IL
OH
OL

IOH = –500µADV

IOL = 500µA 0.4 V

0.65 • DV

DD

–0.3 0.35 • DV

–0.4 V

DD

DVDD + 0.3 V

DD

Offset Binary Two’s Complement

DD

AV

DD

= +5V 0.8 1.15 mA

DD

DV

= +1.8V 0.2 0.4 mA

DD

1.8 3.6 VDC

4.75 5 5.25 VDC

V

PIN CONFIGURATION

Top View SSOP-20

CH1+

CH1–

CH2+

CH2–

CH3+

CH3–

AV

CLK

DV

NC

1

2

3

4

5

ADS1254E

6

7

DD

8

9

DD

10

CH4+

20

19

CH4–

V

18

17

AGND

CHSEL0

16

15

CHSEL1

SCLK

14

13

DOUT/DRDY

12

DGND

11

NC

REF

PIN DESCRIPTIONS

PIN NAME PIN DESCRIPTION

1 CH1+ Analog Input: Positive Input of the Differen-

2 CH1– Analog Input: Negative Input of the Differ-

3 CH2+ Analog Input: Positive Input of the Differen-

4 CH2– Analog Input: Negative Input of the Differ-

5 CH3+ Analog Input: Positive Input of the Differen-

6 CH3– Analog Input: Negative Input of the Differ-

7AV
8 CLK Digital Input: Device System Clock. The

9DV

10 NC No Connection

DD

DD

11 NC No Connection
12 DGND Input: Digital Ground
13 DOUT/DRDY Digital Output: Serial Data Output/Data

14 SCLK Digital Input: Serial Clock. The serial clock

15 CHSEL1 Digital Input: Used to select analog input

16 CHSEL0 Digital Input: Used to select analog input

17 AGND Input: Analog Ground
18 V
19 CH4– Analog Input: Negative Input of the Differ-

REF

20 CH4+ Analog Input: Positive Input of the Differen-

tial Analog Input

ential Analog Input

tial Analog Input

ential Analog Input

tial Analog Input

ential Analog Input
Input: Analog Power Supply Voltage, +5V

system clock is in the form of a CMOS­compatible clock. This is a Schmitt-Trigger
input
Input: Digital Power Supply Voltage

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.

is in the form of a CMOS-compatible clock.
The serial clock operates independently
from the system clock, therefore, it is pos­sible to run SCLK at a higher frequency
than CLK. The normal state of SCLK is
LOW. Holding SCLK HIGH will either ini­tiate a modulator reset for synchronizing
multiple converters or enter power-down
mode. This is a Schmitt-Trigger input.

channel. This is a Schmitt-Trigger Input

channel. This is a Schmitt-Trigger Input

Analog Input: Reference Voltage Input

ential Analog Input

tial Analog Input

ADS1254

SBAS213

3

TYPICAL CHARACTERISTICS

At TA = +25°C, AVDD = +5V, DVDD = +1.8V, CLK = 8MHz, and V

= 4.096, unless otherwise specified.

REF

2.0

1.9

1.8

1.7

1.6

1.5

1.4

1.3

RMS Noise (ppm of FS)

1.2

1.1

1.0
100 1k 10k 100k

2.0

1.8

1.6

1.4

1.2

1.0

0.8

0.6

RMS Noise (ppm of FS)

0.4

0.2

0.0
–40 –20 0 20 40 60 80 100

RMS NOISE vs DATA OUTPUT RATE

Data Ouput Rate (Hz)

RMS NOISE vs TEMPERATURE

Temperature (°C)

EFFECTIVE RESOLUTION vs DATA OUTPUT RATE

20.0

19.8

19.6

19.4

19.2

19.0

18.8

18.6

Effective Resolution (Bits)

18.4

18.2

18.0
100 1k 10k 100k

Data Ouput Rate (Hz)

20

19.8

19.6

19.4

19.2

19.0

18.8

18.6

18.4

Effective Resolution (Bits)

18.2

18.0

EFFECTIVE RESOLUTION vs TEMPERATURE

–40 –20 0 20 40 60 80 100

Temperature (°C)

10

9
8
7
6
5
4

RMS Noise (µV)

3
2
1
0

0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0

RMS NOISE vs V

Voltage (V)

V

REF

4

REF

Voltage

12

10

8

6

4

RMS Noise (ppm of FS)

2

0

0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5

RMS NOISE vs V

V

Voltage (V)

REF

REF

Voltage

ADS1254

SBAS213

TYPICAL CHARACTERISTICS (Cont.)

–0
–10
–20
–30
–40
–50
–60
–70
–80
–90

–100

PSR vs CLK FREQUENCY

Clock Frequency (MHz)

12345678

PSR (dB)

20
18
16
14
12
10

8
6
4
2
0

OFFSET vs TEMPERATURE

Temperature (°C)

–40 –20 0 20 40 60 80 100

DC Offset (ppm of FS)

At TA = +25°C, AVDD = +5V, DVDD = +1.8V, CLK = 8MHz, and V

= 4.096, unless otherwise specified.

REF

2

1.5

1

0.5

RMS Noise (ppm of FS)

0

–5 –4 –3 –2 –10 1 23 4 5

INTEGRAL NON-LINEARITY vs DATA OUTPUT RATE

6

5

4

3

RMS NOISE vs INPUT VOLTAGE

Input Voltage (V)

2.5

INTEGRAL NONLINEARITY vs TEMPERATURE

2.0

1.5

1.0

INL (ppm of FS)

0.5

0

–40 –20 0 20 40 60 80 100

Temperature (°C)

2

INL (ppm of FS)

1

0

100 1k 10k 100k

Data Output Rate (Hz)

600

580

560

540

520

Gain Error (ppm of FS)

500

480

–60 –40 –20 0 20 40 60 80 100

ADS1254

SBAS213

GAIN ERROR vs TEMPERATURE

Temperature (°C)

5

TYPICAL CHARACTERISTICS (Cont.)

At TA = +25°C, AVDD = +5V, DVDD = +1.8V, CLK = 8MHz, and V

= 4.096, unless otherwise specified.

REF

–50

–60

–70

–80

–90

CMR at 60Hz (dB)

–100

–110

012345678

0.9

0.8

0.7

0.6

0.5

0.4

Current (mA)

0.3

0.2

0.1
0

–40 –20 0 20 40 60 80 100

CMR AT 60Hz vs CLK FREQUENCY

Clock Frequency (MHz)

CURRENT vs TEMPERATURE

AVDD (5V)
DV

Temperature (°C)

DD

(1.8V)

–70

–75

–80

–85

CMR (dB)

–90

–95

–100

–105

10 100 1k 10k 100k

4.5

4.0

3.5

3.0

2.5

2.0

1.5

1.0

Power Dissipation (mW)

0.5
0

012345 768

CMR vs COMMON-MODE FREQUENCY

Common-Mode Signal Frequency (Hz)

POWER DISSIPATION vs CLK FREQUENCY

Analog (5V)
Digital (3.3V)
Digital (1.8V)

Clock Frequency (MHz)

V

CURRENT vs CLK FREQUENCY

35

30

25

20

15

Current (µA)

REF

V

10

5

0

012345678

REF

Clock Frequency (MHz)

0

–20
–40
–60

–80
–100
–120

Relative Magnitude (dB)

–140
–160

01234567891011

(1kHz input at 0.1dB less than full-scale)

6

TYPICAL FFT

Input Signal Frequency (kHz)

ADS1254

SBAS213