TEXAS INSTRUMENTS ADS1245 Technical data

Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments

查询ADS1245供应商查询ADS1245供应商

ADS1245

SBAS287A − JUNE 2003 − REVISED SEPTEMBER 2003

Low-Power, 24-Bit

Analog-to-Digital Converter

FEATURES

D 20-Bit Effective Resolution
D High-Impedance Buffered Input
D ±2.5V Differential Input Range
D Pin-Compatible with ADS1244
D 0.0006% INL (typ), 0.0015% INL (max)
D Simple Two-Wire Serial Interface
D Simultaneous 50Hz and 60Hz Rejection
D Single Conversions with Sleep Mode
D Single-Cycle Settling
D Self-Calibration
D Well Suited for Multi-Channel Systems
D Easily Connects to the MSP430
D Current Consumption: 158µA
D Analog Supply: 2.5V to 5.25V
D Digital Supply: 1.8V to 3.6V

APPLICATIONS

D Hand-Held Instrumentation
D Portable Medical Equipment
D Industrial Process Control
D Test and Measurement Systems

DESCRIPTION

The ADS1245 is a 24-bit, delta-sigma analog-to-digital
converter (ADC). It offers excellent performance and very
low power in an MSOP-10 package and is well suited for
demanding high-resolution measurements, especially in
portable and other space- and power-constrained
systems.

The buffered input presents an impedance of 3GΩ, mini-
mizing measurement errors when using high-impedance
sources. The ADS1245 is compatible with ADS1244 and
offers a direct upgrade path for designs requiring higher in­put impedance.

A third-order delta-sigma (∆Σ) modulator and digital filter
form the basis of the ADC. The analog modulator has a
±2.5V differential input range. The digital filter rejects both
50Hz and 60Hz signals, completely settles in one cycle,
and outputs data at 15 samples per second (SPS).

A simple, two-wire serial interface provides all the
necessary control. Data retrieval, self-calibration, and
Sleep mode are handled with a few simple waveforms.
When only single conversions are needed, the ADS1245
can be shut down (Sleep mode) while idle between
measurements to dramatically reduce the overall power
dissipation. Multiple ADS1245s can be connected
together to create a synchronously sampling multichannel
measurement system. The ADS1245 is designed to easily
connect to microcontrollers, such as the MSP430.

The ADS1245 supports 2.5V to 5.25V analog supplies and

1.8V to 3.6V digital supplies. Power is typically less than
470µW in normal operation and less than 1µW during
Sleep mode.

VREFP VREFN AVDD

AINP

AINN

semiconductor products and disclaimers thereto appears at the end of this data sheet.

All trademarks are the property of their respective owners.

         
          
 !     !   

Buffer

3rd−Order
Modulator

Digital

Filter

GND

www.ti.com

DVDD

Serial

Interface

CLK

DRDY/DOUT

SCLK

Copyright  2003, Texas Instruments Incorporated

"#$%&

ADS1245

MSOP-10

DGS

−40°C to +85°C

BHI

SBAS287A − JUNE 2003 − REVISED SEPTEMBER 2003

ORDERING INFORMATION

PRODUCT PACKAGE−LEAD

(1)

For the most current specifications and package information, refer to our web site at www.ti.com.

PACKAGE

DESIGNATOR

(1)

SPECIFIED

TEMPERATURE

RANGE

PACKAGE

MARKING

www.ti.com

ORDERING

NUMBER

ADS1245IDGST Tape and Reel, 250
ADS1245IDGSR Tape and Reel, 2500

TRANSPORT

MEDIA, QUANTITY

ABSOLUTE MAXIMUM RATINGS

over operat i n g f ree-air temperature range unless otherwise noted

ADS1245 UNIT

AVDD to GND −0.3 to +6 V
DVDD to GND −0.3 to +3.6 V
Input Current 100, momentary mA
Input Current 10, continuous mA
Analog Input Voltage to GND −0.5 to AVDD + 0.5 V
Analog Input Voltage to GND −0.3 to DVDD + 0.3 V
Digital Output Voltage to GND −0.3 to DVDD + 0.3 V
Maximum Junction Temperature +150 °C
Operating Temperature Range −40 to +85 °C
Storage Temperature Range −60 to +150 °C
Lead Tem perature (soldering, 10s) +300 °C

(1)

Stresses above these ratings may cause permanent damage.
Exposure to absolute maximum conditions for extended periods
may degrade device reliability. These are stress ratings only , an d
functional operation of the device at these or any other conditions
beyond those specified is not implied.

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 t o damage because very small parametric changes could
cause the device not to meet its published specifications.

(1)

PIN ASSIGNMENTS

DGS PACKAGE

MSOP

(TOP VIEW)

ADS1245

GND
VREFP
VREFN

AINN
AINP

1
2
3
4
5

10

9
8
7
6

CLK
SCLK
DRDY/DOUT
DVDD
AVDD

Terminal Functions

TERMINAL

NAME NO. DESCRIPTION

GND 1 Analog and digital ground
VREFP 2 Positive reference input
VREFN 3 Negative reference input
AINN 4 Negative analog input
AINP 5 Positive analog input
AVDD 6 Analog power supply, 2.5V to 5.25V
DVDD 7 Digital power supply, 1.8V to 3.6V
DRDY/DOUT 8 Dual-purpose output:

Data ready: indicates valid data by going low.
Data output: outputs data, MSB first, on the
first rising edge of SCLK.

SCLK 9 Serial clock input: clocks out data on the

rising edge. Used to initiate calibration and
Sleep mode (see text for more details).

CLK 10 System clock input: typically 2.4576MHz

2

www.ti.com

Common-mode rejection
Normal-mode rejection

Logic levels

AVDD current

DVDD current

SBAS287A − JUNE 2003 − REVISED SEPTEMBER 2003

"#$%&

ELECTRICAL CHARACTERISTICS

All specifications at TA = −40°C to +85°C, AVDD = +5V, DVDD = +3V, f

PARAMETER TEST CONDITIONS MIN TYP MAX UNIT

Analog Input

Full-scale input voltage range AINP − AINN ±2V
Absolute input range AINP, AINN with respect to GND GND + 0.1 AVDD − 1.25 V
Differential input impedance f

System Performance

Resolution No missing codes 24 Bits
Data rate f
Integral nonlinearity (INL) Differential input signal, end point fit ±0.0006 ±0.0015 %FSR
Offset error 1 14 ppm of FSR
Offset error drift
Gain error
Gain error drift

Common-mode rejection

Input referred noise 2
Analog power-supply rejection At DC, ∆AVDD = 5% 100 dB

Digital power-supply rejection At DC, ∆AVDD = 5% 100 dB

Voltage Reference Input

Reference input voltage (V
Negative reference input (VREFN) GND − 0.1 VREFP − 0.5 V
Positive reference input (VREFP) VREFN + 0.5 AVDD + 0.1 V
Voltage reference impedance f

Digital Input/Output

Input leakage (CLK, SCLK) 0 < (CLK, SCLK) < DVDD ±10 µA
CLK frequency (f
CLK duty cycle 30 70 %

Power Supply

AVDD 2.7 5.25 V
DVDD 1.8 3.6 V

AVDD current

DVDD current

Total power dissipation AVDD = DVDD = 3V 0.47 mW
(1)

SPS = samples per second.

(2)

FSR = full-scale range = 4V

(3)

Recalibration can reduce these errors to the level of the noise.

(4)

Achieving specified gain error performance requires that calibration be performed with reference voltage input between (GND + 0.1V) and
(AVDD − 1.25V). See Voltage Reference Inputs section.

(5)

fCM is the frequency of the common-mode input.

(6)

f

SIG

(7)

It will not be possible to reach the digital output full-scale code when VIN > 2V

(3)

(4)

(3)

) V

REF

VIH (CLK, SCLK) 0.8 DVDD 5.25 V
VIL (CLK, SCLK) GND 0.2 DVDD V
VOH (DRDY, DOUT) IOH = 1mA DVDD − 0.4 DVDD V
VOL (DRDY, DOUT) IOL = 1mA GND DVDD + 0.4 V

) 6 MHz

CLK

.

REF

is the frequency of the input signal.

= 2.4576MHz 3 GΩ

CLK

= 2.4576MHz 15 SPS

CLK

At DC 90 100 dB

(5)

f

= 50 ± 1Hz, f

CM

fCM = 60 ± 1Hz, f

(6)

f

= 50 ± 1Hz, f

SIG

f

= 60 ± 1Hz, f

SIG

≡ VREFP − VREFN 0.5 1.25 AVDD

REF

= 2.4576MHz 1 MΩ

CLK

Sleep mode 0.1 1 µA
AVDD = 3V 152 µA
AVDD = 5V 158 250 µA
Sleep mode, CLK stopped 0.1 µA
Sleep mode, 2.4576MHZ CLK running 1.6 5 µA
DVDD = 3V 5 10 µA

CLK

= 2.4576MHz 100 dB

CLK

CLK

= 2.4576MHz 70 dB

CLK

= 2.4576MHz, and V

CLK

= 2.4576MHz 100 dB

= 2.4576MHz 60 dB

.

REF

= +1.25V , unless otherwise noted.

REF

REF

0.01 ppm of FSR/°C

0.005 0.1 %

0.5 ppm/°C

(7)

ppm of FSR,

RMS

V

(1)

V

(2)

3

"#$%&

ANALOG CURRENT vs ANALOG SUPPLY

SBAS287A − JUNE 2003 − REVISED SEPTEMBER 2003

TYPICAL CHARACTERISTICS

At TA = +25°C, AVDD = +5V, DVDD = +3V, f

CLK

= 2.4576MHz, and V

= +1.25V , unless otherwise specified.

REF

www.ti.com

220
210
200
190
180

A)

µ

170
160
150

Current (

140
130
120
110
100

−

ANALOG CURRENT vs TEMPERATURE

AVDD = +5V, f

−

−

45

5

25 35 55 75 95

= 4.9152MHz

CLK

AVDD = +3V, f

15

Temp erature (_C)

CLK

=2.4576MHz

12

10

8

A)

µ

6

Current (

4

2

0

−

45

Figure 1

164
162
160

A)

158

µ

156
154

Current(

152
150
148

f

=4.9152Hz

CLK

f

=2.4576MHz

CLK

Analog Supply (V)

4.03.53.0 4.5 5.0 5.52.5

16
14
12

A)

10

µ

8
6

Current (

4
2
0

−

DIGITALCURRENT vs TEMPERATURE

DVDD = +3V, f

DVDD = +1.8V, f

−

−

25 35 55 75 95

15

5

Temperature (_C)

= 4.9152MHz

CLK

CLK

Figure 2

DIGITALCURRENT vs DIGITALSUPPLY

f

= 4.9152MHz

CLK

f

= 2.4576MHz

CLK

−

−

25 35 55 75 95

45

15

5

Digital Supply (V)

= 2.4576MHz

Figure 3

INTEGRAL NONLINEARITY vs ANALOG SUPPLY

= 2.4 or (( 1.8)/2 + 0.3), whichever is smaller

V

CM

30

25

20

15

10

INL (ppm of FSR)

5

0

T=+85_C

V

REF

AVDD

= 1.25; f

−

AVDD

Figure 5

4

= 2.4576MHz

OSC

T= 40_C−

T=+25_C

4.03.53.0 4.5 5.0 5.52.5
(V)

Figure 4

12.5

10.0

7.5

5.0

2.5
0

−

2.5

INL (ppm of FSR)

−

5.0

−

7.5

−

10.0

−

12.5

−

2.5

INTEGRAL NONLINEARITY vs V

T=+25_C

T=+85_C

T=−40_C

−

1.5

−

0.5 0.5 1.5 2.5
VIN(V)

IN

Figure 6

www.ti.com

OFFSET vs TEMPERATURE

GAIN vs TEMPERATURE

Gain (Normalized)

HISTOGRAM OF OUTPUT DATA

TYPICAL CHARACTERISTICS

At TA = +25°C, AVDD = +5V, DVDD = +3V, f

= 2.4576MHz, and V

CLK

SBAS287A − JUNE 2003 − REVISED SEPTEMBER 2003

= +1.25V , unless otherwise specified.

REF

"#$%&

5
4
3
2
1
0

−

1

−

2

−

3

Normalized Offset (ppm of FSR)

−

4

−

5

−

45

−

−

25 35 55 75 95

15

5

Temperat ure (_C)

Figure 7

3.2

3.0

2.8

2.6

2.4

2.2

2.0

1.8

Noise (ppm of FSR, RMS)

1.6

1.4

1.2

−

2.5

NOISE vs INPUT SIGNAL

−

1.5

−

0.5 0.5 1.5 2.5
VIN(V)

1.00006

1.00005

1.00004

1.00003

1.00002

1.00001

1.00000

0.99999

0.99998

0.99997

0.99996

0.99995

0.99994

3.0

2.5

2.0

1.5

1.0

Noise (ppm of FSR, RMS)

0.5

−

25 35 55 75 95

45

15

5

Temperature (_C)

−

−

Figure 8

NOISE vs TEMPERATURE

0

−

45

−

−

25 35 55 75 95

15

5

Temperature (_C)

Figure 9

COMMON−MODE REJECTION RATIO

900
800
700
600
500
400
300

Number of Occurences

200
100

0

10

−9−8−7−6−5−4−3−2−

−14−12−

1

012345678

ppmof FSR

Figure 11

9

101112

160
140
120
100

80

CMRR (dB)

60
40
20

0

Figure 10

vs FREQUENCY

1k10010 10k 100k1

Frequency (Hz)

Figure 12

5

"#$%&

ANALOGPOWER−SUPPLY REJECTION RATIO

SBAS287A − JUNE 2003 − REVISED SEPTEMBER 2003

TYPICAL CHARACTERISTICS

At TA = +25°C, AVDD = +5V, DVDD = +3V, f

CLK

= 2.4576MHz, and V

= +1.25V , unless otherwise specified.

REF

www.ti.com

DIGITALPOWER−SUPPLYREJECTION RATIO

140

120

100

80

60

PSRR (dB)

40

20

0

vs FREQUENCY

1k10010 10k 100k1

Frequency (Hz)

140

120

100

80

60

PSRR (dB)

40

20

0

Figure 13

vs FREQUENCY

1k10010 10k 100k1

Frequency (Hz)

Figure 14

6