Datasheet

ManualsBrandsTEXAS INSTRUMENTS ManualsData collecting ICsData acquisition IC - AD converter (ADC) External SOIC 16 N

24-Bit

ADCDS

VREFP VREFN

CAP DVDD

GND

AINP

AINN

SCLK

SPEED

DRDY/DOUT

PDWN

AVDD

Internal

Oscillator

G=128

CAP

CLKIN

EMI

Filter

ADS1231

www.ti.com

SBAS414D –JULY 2009–REVISED OCTOBER 2013

24-Bit Analog-to-Digital Converter

for Bridge Sensors

Check for Samples: ADS1231

FEATURES

DESCRIPTION

The ADS1231 is a precision, 24-bit analog-to-digital

• Complete Front-End for Bridge Sensors

converter (ADC). With an onboard low-noise

• Internal Amplifier, Gain of 128

amplifier, onboard oscillator, precision third-order 24-

• Internal Oscillator

bit delta-sigma (ΔΣ) modulator, and bridge power

switch, the ADS1231 provides a complete front-end

• Low-Side Power Switch for Bridge Sensor

solution for bridge sensor applications including

• Low Noise: 35nVrms

weigh scales, strain gauges, and load cells.

• Selectable Data Rates: 10SPS or 80SPS

The low-noise amplifier has a gain of 128, supporting

• Simultaneous 50Hz and 60Hz Rejection at

a full-scale differential input of ±19.5mV. The ΔΣ ADC

10SPS

has 24-bit resolution and is comprised of a third-order

• Input EMI Filter

modulator and fourth-order digital filter. Two data

rates are supported: 10SPS (with both 50Hz and

• External Voltage Reference up to 5V for

60Hz rejection) and 80SPS. The ADS1231 can be

Ratiometric Measurements

put in a low-power standby mode or shut off

• Simple, Pin-Driven Control

completely in power-down mode.

• Two-Wire Serial Digital Interface

The ADS1231 is controlled by dedicated pins; there

• Supply Range: 3V to 5.3V

are no digital registers to program. Data are output

over an easily-isolated serial interface that connects

• Package: SOIC-16

directly to the MSP430 and other microcontrollers.

• Temperature Range: –40°C to +85°C

The ADS1231 is available in an SO-16 package and

APPLICATIONS is specified from –40°C to +85°C.

• Weigh Scales

• Strain Gauges

• Load Cells

• Industrial Process Control

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.

2All 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.

Summary of content (23 pages)

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ADS1231 www.ti.com SBAS414D – JULY 2009 – REVISED OCTOBER 2013 24-Bit Analog-to-Digital Converter for Bridge Sensors Check for Samples: ADS1231 FEATURES DESCRIPTION • • • • • • • The ADS1231 is a precision, 24-bit analog-to-digital converter (ADC).
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ADS1231 SBAS414D – JULY 2009 – REVISED OCTOBER 2013 www.ti.com 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.
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ADS1231 www.ti.com SBAS414D – JULY 2009 – REVISED OCTOBER 2013 ELECTRICAL CHARACTERISTICS Minimum/maximum limit specifications apply from –40°C to +85°C. Typical specifications at +25°C. All specifications at AVDD = DVDD = VREFP = +5V, VCM = 2.5V and VREFN = GND, unless otherwise noted. ADS1231 PARAMETER CONDITIONS MIN TYP MAX UNIT ANALOG INPUTS Full-scale input voltage (AINP – AINN) ±0.5VREF / 128 V VREF = AVDD = 5V ±19.5 mV VREF = AVDD = 3V ±11.7 mV Common-mode input range GND + 1.
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ADS1231 SBAS414D – JULY 2009 – REVISED OCTOBER 2013 www.ti.com ELECTRICAL CHARACTERISTICS (continued) Minimum/maximum limit specifications apply from –40°C to +85°C. Typical specifications at +25°C. All specifications at AVDD = DVDD = VREFP = +5V, VCM = 2.5V and VREFN = GND, unless otherwise noted. ADS1231 PARAMETER CONDITIONS MIN TYP MAX UNIT POWER SUPPLY Power-supply voltage (AVDD, DVDD) 3 V 900 μA Normal mode, AVDD = 5V 900 μA Standby mode 0.1 μA Power-down 0.
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ADS1231 www.ti.com SBAS414D – JULY 2009 – REVISED OCTOBER 2013 PIN CONFIGURATION D PACKAGE SO-16 (TOP VIEW) DVDD 1 16 DRDY/DOUT GND 2 15 SCLK CLKIN 3 14 PDWN SPEED 4 13 AVDD CAP 5 12 SW CAP 6 11 GND AINP 7 10 VREFP AINN 8 9 VREFN PIN DESCRIPTIONS NAME TERMINAL ANALOG/DIGITAL INPUT/OUTPUT DVDD 1 Digital Digital power supply GND 2 Supply Ground for digital and analog supplies CLKIN 3 Digital input DESCRIPTION External clock input: typically 4.9152MHz.
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ADS1231 SBAS414D – JULY 2009 – REVISED OCTOBER 2013 www.ti.com NOISE PERFORMANCE The ADS1231 offers outstanding noise performance. Table 1 summarizes the typical noise performance with inputs shorted externally for different data rates and voltage reference values. The RMS and Peak-to-Peak noise are referred to the input.
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ADS1231 www.ti.com SBAS414D – JULY 2009 – REVISED OCTOBER 2013 TYPICAL CHARACTERISTICS At TA = +25°C, AVDD = DVDD = REFP = 5V, REFN = GND, and VCM = 2.5V unless otherwise noted.
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ADS1231 SBAS414D – JULY 2009 – REVISED OCTOBER 2013 www.ti.com TYPICAL CHARACTERISTICS (continued) At TA = +25°C, AVDD = DVDD = REFP = 5V, REFN = GND, and VCM = 2.5V unless otherwise noted. GAIN ERROR vs TEMPERATURE 0.02 1500 0.015 1000 0.01 Gain Error (%) Offset (nV) OFFSET DRIFT vs TEMPERATURE 2000 500 0 -500 0.005 0 -0.005 -1000 -0.01 -1500 -0.015 -2000 -0.02 10 -40 -27.5 -15 -2.5 22.5 35 47.5 60 85 72.5 -40 -27.5 -15 -2.5 22.5 47.5 35 Temperature (°C) Figure 7. Figure 8.
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ADS1231 www.ti.com SBAS414D – JULY 2009 – REVISED OCTOBER 2013 OVERVIEW The ADS1231 is a precision, 24-bit ADC that includes a low-noise PGA, internal oscillator, third-order deltasigma (ΔΣ) modulator, and fourth-order digital filter. The ADS1231 provides a complete front-end solution for bridge sensor applications such as weigh scales, strain gauges, and pressure sensors. Data can be output at 10SPS for excellent 50Hz and 60Hz rejection, or at 80SPS when higher speeds are needed.
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ADS1231 SBAS414D – JULY 2009 – REVISED OCTOBER 2013 www.ti.com LOW-SIDE POWER SWITCH (SW) CLOCK SOURCE The ADS1231 incorporates an internal switch for use with an external bridge sensor, as shown in Figure 15. The switch can be used in a return path for the bridge power. By opening the switch, power dissipation in the bridge is eliminated. The ADS1231 can use the internal oscillator or an external clock source to accommodate a wide variety of applications.
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ADS1231 www.ti.com SBAS414D – JULY 2009 – REVISED OCTOBER 2013 FREQUENCY RESPONSE 0 Data Rate = 10SPS 4 -50 Gain (dB) The ADS1231 uses a sinc digital filter with the frequency response shown in Figure 17 for fCLKIN = 4.9152MHz. The frequency response repeats at multiples of the modulator sampling frequency of 76.8kHz. The overall response is that of a low-pass filter with a –3dB cutoff frequency of 3.32Hz with the SPEED pin tied low (10SPS data rate) and 11.
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ADS1231 SBAS414D – JULY 2009 – REVISED OCTOBER 2013 www.ti.com Table 2. Data Rate Settings SETTLING TIME Fast changes in the input signal require time to settle. For example, an external multiplexer in front of the ADS1231 can generate abrupt changes in input voltage by simply switching the multiplexer input channels. These sorts of changes in the input require four data conversion cycles to settle. When continuously converting, five readings may be necessary in order to settle the data.
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ADS1231 www.ti.com SBAS414D – JULY 2009 – REVISED OCTOBER 2013 DATA READY/DATA OUTPUT (DRDY/DOUT) DATA RETRIEVAL This digital output pin serves two purposes. First, it indicates when new data are ready by going low. Afterwards, on the first rising edge of SCLK, the DRDY/DOUT pin changes function and begins outputting the conversion data, most significant bit (MSB) first. Data are shifted out on each subsequent SCLK rising edge.
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ADS1231 SBAS414D – JULY 2009 – REVISED OCTOBER 2013 www.ti.com STANDBY MODE When tSTANDBY has passed with SCLK held high, Standby mode activates. DRDY/DOUT stays high when Standby mode begins. SCLK must remain high to stay in Standby mode. To exit Standby mode (wake up), set SCLK low. The first data after exiting Standby mode are valid. Standby mode dramatically reduces power consumption by shutting down most of the circuitry.
PAGE 15
ADS1231 www.ti.com SBAS414D – JULY 2009 – REVISED OCTOBER 2013 POWER-DOWN MODE Power-Down mode shuts down the entire ADC circuitry and reduces the total power consumption close to zero. To enter Power-Down mode, simply hold the PDWN pin low. Power-Down mode also resets the entire circuitry. Power-Down mode can be initiated at any time during readback; it is not necessary to retrieve all 24 bits of data beforehand. Figure 23 shows the wake-up timing from PowerDown mode. AVDD DVDD PDWN ³ 10ms Figure 22.
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ADS1231 SBAS414D – JULY 2009 – REVISED OCTOBER 2013 www.ti.com APPLICATION EXAMPLE Weigh Scale System Figure 24 shows a typical ADS1231 application as part of a weigh scale system. 3V to 5.3V 3V (1) 1mF 13 AVDD 10 5 - VREFP CAP DRDY/DOUT 0.1mF 6 SCLK CAP + ADS1231 7 8 VDD DVDD (2) Load Cell (1) 1mF 1 PDWN SPEED AINP 16 15 14 MSP430x4xx 4 AINN 9 VREFN 12 CLKIN SW 3 GND GND 2, 11 (1) Place a 0.1μF or higher capacitor as close as possible on both AVDD and DVDD.
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ADS1231 www.ti.com SBAS414D – JULY 2009 – REVISED OCTOBER 2013 REVISION HISTORY NOTE: Page numbers for previous revisions may differ from page numbers in the current version. Changes from Revision C (December 2010) to Revision D Page • Changed "oscillator" to "clock" in data rate parameter of electrical characteristics .............................................................. 3 • Changed all "fCLK" to "fCLKIN" throughout data sheet ................................................................
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PACKAGE OPTION ADDENDUM www.ti.
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PACKAGE MATERIALS INFORMATION www.ti.com 9-Oct-2013 TAPE AND REEL INFORMATION *All dimensions are nominal Device ADS1231IDR Package Package Pins Type Drawing SOIC D 16 SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) 2500 330.0 16.4 Pack Materials-Page 1 6.5 B0 (mm) K0 (mm) P1 (mm) 10.3 2.1 8.0 W Pin1 (mm) Quadrant 16.
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PACKAGE MATERIALS INFORMATION www.ti.com 9-Oct-2013 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) ADS1231IDR SOIC D 16 2500 333.2 345.9 28.
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