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ADS1226 Schematic ( PDF Datasheet ) - Burr-Brown

Teilenummer ADS1226
Beschreibung (ADS1225 / ADS1226) 24-Bit Analog-to-Digital Converter
Hersteller Burr-Brown
Logo Burr-Brown Logo 




Gesamt 24 Seiten
ADS1226 Datasheet, Funktion
www.DataSheet4U.com
BurrĆBrown Products
from Texas Instruments
ADS1225 ¨
ADS1226 ¨
ADS1225
ADS1226
SBAS346 – MAY 2006
24-Bit Analog-to-Digital Converter
with One- and Two-Channel Differential Inputs and Internal Oscillator
FEATURES
100SPS Data Rate (High-Speed Mode)
Single-Cycle Settling
Easy Conversion Control with START Pin
Automatic Shutdown
Low Noise: 4µVRMS Noise (High-Resolution
Mode)
Input Multiplexer with Two Differential
Channels (ADS1226)
Voltage Reference Supports Ratiometric
Measurements
Self-Calibrating
Simple Read-Only 2-Wire Serial Interface
Internal High-Impedance Input Buffer
Internal Temperature Sensor
Internal Oscillator
Low-Power: 1mW While Operating, < 1µA
During Shutdown
Analog and Digital Supplies: 2.7V to 5.5V
APPLICATIONS
Hand-Held Instrumentation
Portable Medical Equipment
Industrial Process Control
TEMPEN
AVDD
DESCRIPTION
The ADS1225 and ADS1226 are 24-bit delta-sigma
analog-to-digital (A/D) converters. They offer
excellent performance, ease-of-use, and low power
in a small 4mm × 4mm QFN package and are
well-suited for demanding high-resolution
measurements, especially in portable and other
space-saving and power-constrained applications.
The ADS1225 and ADS1226 convert on command
using a dedicated START pin. Simply pulse this pin
to initiate a conversion. Data is read in a single cycle
for retrieval over a 2-wire serial interface that easily
connects to popular microcontrollers like the
MSP430. After the conversion completes, the
ADS1225 and ADS1226 automatically shuts down all
circuitry.
Internal features include a two-channel multiplexer
(ADS1226), selectable input buffer, temperature
sensor, and oscillator. The full-scale range is defined
by the external voltage reference with support
provided for up to a 5V differential input signal. Two
operating modes allow for speed (100SPS data rate,
15µVRMS noise) or resolution (4µVRMS noise, 16SPS
data rate).
The ADS1225/6 supports 2.7 to 5.5V analog and
digital supplies. Power consumption is 1mW while
converting with 3V supplies. The ADS1225 and
ADS1226 are fully specified over an extended
industrial temperature range of –40°C to +105°C.
VREFP VREFN DVDD
AINP1
AINN1
AINP2
AINN2
MUX
Buffer
START
DS
ADC
Serial Interface
SCLK
DRDY/DOUT
Oscillator
MODE
MUX
ADS1226 Only
BUFEN
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.
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 the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2006, Texas Instruments Incorporated






ADS1226 Datasheet, Funktion
ADS1225
ADS1226
SBAS346 – MAY 2006
RGV PACKAGE
QFN-16 4.0mm x 4.0mm
(TOP VIEW)
www.ti.com
START 1
SCLK 2
DRDY/DOUT 3
BUFEN 4
ADS1226
12 GND
11 AINN1
10 AINP1
9 AINN2
NAME
START
SCLK
TERMINAL
NO.
1
2
DRDY/DOUT
3
BUFEN
MUX
TEMPEN
MODE
AINP2
AINN2
AINP1
AINN1
GND
VREFN
VREFP
AVDD
DVDD
4
5
6
7
8
9
10
11
12
13
14
15
16
PIN DESCRIPTIONS – ADS1226
ANALOG/DIGITAL
INPUT/OUTPUT
Digital Input
Digital Input
Digital Output
Digital Input
Digital Input
Digital Input
Digital Input
Analog Input
Analog Input
Analog Input
Analog Input
Ground
Analog Input
Analog Input
Analog
Digital
DESCRIPTION
High: Start conversions; Low: Shutdown
Serial clock input
Dual-purpose output:
Data ready: indicates valid data by going low.
Data output: outputs data, MSB first, on the rising edge of SCLK.
Enables buffer after MUX
Selects analog input from MUX
Selects temperature sensor input from MUX
Selects between High-Speed and High-Resolution modes
Analog channel 2 positive input
Analog channel 2 negative input
Analog channel 1 positive input
Analog channel 1 negative input
Analog and digital ground
Negative reference input
Positive reference input
Analog power supply
Digital power supply
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ADS1226 pdf, datenblatt
ADS1225
ADS1226
SBAS346 – MAY 2006
TEMPERATURE SENSOR
Internal diodes provide temperature-sensing
capability. By setting the TEMPEN pin high, the
selected analog inputs are disconnected and the
inputs to the A/D converter are connected to the
anodes of two diodes scaled to 1x and 64x in current
and size inside the MUX, as shown in Figure 24. By
measuring the difference in voltage of these diodes,
temperature changes can be inferred from a baseline
temperature. Typically, the difference in diode
voltages is 106mV at +25°C, with a temperature
coefficient of 360µV/°C. A similar structure is used in
the MSC1210 for temperature measurement. For
more information, see TI application report
SBAA100, Using the MSC121x as a High-Precision
Intelligent Temperature Sensor, available for
download at www.ti.com.
AVDD
TEMPEN
8I 1I
1X 8X
AINP
AINN
AINP1
AINN1
AINP2
AINN2
MUX
Figure 24. Measurement of the Temperature
Sensor in the Input
www.ti.com
VOLTAGE REFERENCE INPUTS
(VREFP, VREFN)
The voltage reference used by the modulator is
generated from the voltage difference between
VREFP and VREFN: VREF = VREFP – VREFN. The
reference inputs use a structure similar to that of the
analog inputs. A simplified diagram of the circuitry on
the reference inputs is shown in Figure 25. The
switches and capacitors can be modeled with an
effective impedance of 250k.
VREFP
VREFN
AVDD
16pF
AVDD
ESD
Protection
Zeff = 500kW
Figure 25. Simplified Reference Input Circuitry
ESD diodes protect the reference inputs. To prevent
these diodes from turning on, make sure the
voltages on the reference pins do not go below GND
by more than 100mV, and likewise, do not exceed
VDD by 100mV. This limitation is shown in
Equation 2:
GND * 100mV t (VREFP, VREFN) t VDD ) 100mV
(2)
For best performance, bypass the voltage reference
inputs with a 0.1µF capacitor between VREFP and
VREFN. Place the capacitor as close as possible to
the pins.
The differential voltage reference inputs and the wide
range of operation (VREF can support up to AVDD)
make ratiometric measurements easy to implement.
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