Burr Brown Products
from Texas Instruments
BD0
ADS1000
SBAS357 – SEPTEMBER 2006
LOW POWER, 12-Bit ANALOG-TO-DIGITAL CONVERTER
with I
2
C™ INTERFACE
FEATURES
•
•
•
•
•
•
•
•
•
Complete 12-Bit Data Acquisition System in
a Tiny SOT-23 Package
Low Current Consumption: Only 90µA
Integral Nonlinearity: 1LSB Max
Single-Cycle Conversion
Programmable Gain Amplifier
Gain = 1, 2, 4 or 8
128SPS Data Rate
I
2
C Interface with Two Available Addresses
Power Supply: 2.7V to 5.5V
Pin- and Software-Compatible with 16-Bit
ADS1100
DESCRIPTION
The ADS1000 is an I
2
C-compatible serial interface
Analog-to-Digital (A/D) converter with differential
inputs and 12 bits of resolution in a tiny SOT23-6
package. Conversions are performed ratiometrically,
using the power supply as the reference voltage. The
ADS1000 operates from a single power supply
ranging from 2.7V to 5.5V.
The ADS1000 performs conversions at a rate of 128
samples per second (SPS). The onboard
programmable gain amplifier (PGA), which offers
gains of up to 8, allows smaller signals to be
measured with high resolution. In single-conversion
mode, the ADS1000 automatically powers down after
a conversion, greatly reducing current consumption
during idle periods.
The ADS1000 is designed for applications where
space and power consumption are major
considerations. Typical applications include portable
instrumentation, consumer goods, and voltage
monitoring.
APPLICATIONS
•
•
•
•
•
Voltage Monitors
Battery Management
Industrial Process Control
Consumer Goods
Temperature Measurement
V
DD
A = 1, 2, 4, or 8
V
IN+
PGA
V
IN-
A/D
Converter
IC
Interface
2
SCL
SDA
Clock
Oscillator
ADS1000
GND
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.
I2C is a trademark of Royal Philips Electronics B.V., The Netherlands.
All other 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 the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2006, Texas Instruments Incorporated
ADS1000
www.ti.com
SBAS357 – SEPTEMBER 2006
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.
PACKAGE/ORDERING INFORMATION
For the most current package and ordering information, see the Package Option Addendum located at the end
of this datasheet or see the TI website at
www.ti.com.
ABSOLUTE MAXIMUM RATINGS
(1)
over operating free-air temperature range (unless otherwise noted)
ADS1000
V
DD
to GND
Input Current (Momentary)
Input Current (Continuous)
Voltage to GND, V
IN+
, V
IN–
Voltage to GND, SDA, SCL
Maximum Junction Temperature, T
J
Operating Temperature
Storage Temperature
Lead Temperature (soldering, 10s)
(1)
–0.3 to +6
100
10
–0.3 to V
DD
to +0.3
–0.5 to +6
+150
–40 to +125
–60 to +150
+300
UNIT
V
mA
mA
V
V
°C
°C
°C
°C
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.
PIN CONFIGURATION
V
IN-
V
DD
SDA
6
5
4
V
IN-
V
DD
SDA
6
5
4
BD0
1
2
3
V
IN+
GND SCL
I C address: 1001000
2
2
BD1
1
2
3
V
IN+
GND SCL
I C address: 1001001
NOTE: Marking text direction indicates pin 1. Marking text depends on I C address; see Package Option Addendum.
2
2
ADS1000
www.ti.com
SBAS357 – SEPTEMBER 2006
THEORY OF OPERATION
The ADS1000 is a fully differential, 12-bit A/D
converter. The ADS1000 allows users to obtain
precise measurements with a minimum of effort, and
the device is extremely easy to design with and
configure.
The ADS1000 consists of an A/D converter core with
adjustable gain, a clock generator, and an I
2
C
interface. Each of these blocks are described in
detail in the sections that follow.
places the result in the output register, and
immediately begins another conversion. When the
ADS1000 is in continuous conversion mode, the
ST/BSY bit in the configuration register always reads
'1'.
In single conversion mode, the ADS1000 waits until
the ST/BSY bit in the conversion register is set to '1'.
When this happens, the ADS1000 powers up and
performs a single conversion. After the conversion
completes, the ADS1000 places the result in the
output register, resets the ST/BSY bit to '0' and
powers down. Writing a '1' to ST/BSY while a
conversion is in progress has no effect.
When switching from continuous conversion mode to
single conversion mode, the ADS1000 will complete
the current conversion, reset the ST/BSY bit to '0'
and power-down the device.
RESET AND POWER-UP
When the ADS1000 powers up, it automatically
performs a reset. As part of the reset, the ADS1000
sets all of the bits in the configuration register to their
respective default settings.
The ADS1000 responds to the I
2
C General Call
Reset command. When the ADS1000 receives a
General Call Reset, it performs an internal reset,
exactly as though it had just been powered on.
I
2
C INTERFACE
The ADS1000 communicates through an I
2
C
(Inter-Integrated Circuit) interface. The I
2
C interface
is a two-wire, open-drain interface supporting
multiple devices and masters on a single bus.
Devices on the I
2
C bus only drive the bus lines low,
by connecting them to ground; they never drive the
bus lines high. Instead, the bus wires are pulled high
by pull-up resistors, so the bus wires are high when
no device is driving them low. This way, two devices
cannot conflict; if two devices drive the bus
simultaneously, there is no driver contention.
Communication on the I
2
C bus always takes place
between two devices, one acting as the master and
the other acting as the slave. Both masters and
slaves can read and write, but slaves can only do so
under the direction of the master. Some I
2
C devices
can act as masters or slaves, but the ADS1000 can
only act as a slave device.
ANALOG-TO-DIGITAL CONVERTER
The ADS1000 uses a switched-capacitor input stage.
To external circuitry, it looks roughly like a
resistance. The resistance value depends on the
capacitor values and the rate at which they are
switched. The switching clock is generated by the
onboard clock generator, so its frequency, nominally
275kHz, is dependent on supply voltage and
temperature. The capacitor values depend on the
PGA setting.
The common-mode and differential input impedances
are different. For a gain setting of PGA, the
differential input impedance is typically 2.4MΩ/PGA.
The common-mode impedance is typically 8MΩ.
OUTPUT CODE CALCULATION
The ADS1000 outputs codes in binary two’s
complement format. The output code is confined to
the range of numbers: –2048 to 2047, and is given
by:
Output Code
+
2048(PGA)
V
IN)
*V
IN
−
V
DD
CLOCK GENERATOR
The ADS1000 features an onboard clock generator.
The
Typical Characteristics
show variations in data
rate over supply voltage and temperature. It is not
possible to operate the ADS1000 with an external
clock.
USING THE ADS1000
OPERATING MODES
The ADS1000 operates in one of two modes:
continuous conversion and single conversion.
In continuous conversion mode, the ADS1000
continuously performs conversions. Once a
conversion has been completed, the ADS1000
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