Datasheet

ManualsBrandsTEXAS INSTRUMENTS ManualsData collecting ICsData acquisition IC - AD converter (ADC) External , Internal QFN 20

Buffer

Internal

Reference

Internal

Temperature

Sensor

REF

DGND

AIN0

AIN1

AIN2

AIN3

AIN4

AIN5

AIN6

AIN7

Control

Logic

and

Sequencer

SCLK

DOUT

DIN

PDRST/

TM_BUSY

ADC

DVDDAVDD

ADS8028

www.ti.com

SBAS549B –MAY 2011–REVISED MARCH 2012

12-Bit, 1-MSPS, 8-Channel, SAR ADC

with Internal Reference and Internal Temperature Sensor

Check for Samples: ADS8028

FEATURES

DESCRIPTION

The ADS8028 is a 12-bit analog-to-digital converter

• Outstanding Performance:

(ADC), capable of operating at sampling speeds up to

– Throughput: Up to 1 MSPS

1 MSPS. The device is based on a successive

– No Missing Codes: 12 Bits

approximation register (SAR) core and provides an

inherent sample-and-hold (SH) front-end.

– INL: ±0.5 LSB

– SNR: 72 dB

In addition to having eight analog input channels, the

ADS8028 offers an internal temperature sensor with

• Highly Integrated:

0.25°C resolution and an internal voltage reference. A

– Eight Analog Inputs

nine-channel internal multiplexer enables multiple

– High-Resolution Internal Temperature

channels to be selected (including the internal

Sensor

temperature sensor) that are indefinitely scanned in a

sequential manner. A simple SPI-compatible serial

– Nine-Channel Multiplexer with Channel

interface provides easy communication and control

Sequencer

between the device and host controller. The digital

– Low-Drift Internal Voltage Reference

supply can operate from 1.65 V to 5.25 V, enabling

• Wide Supply Range:

direct interface with a wide range of processors and

controllers.

– Analog Supply (AVDD): 2.7 V to 5.25 V

At full speed of 1 MSPS, the ADS8028 dissipates

– Digital Supply (DVDD): 1.65 V to 5.25 V

only 17 mW. The device offers flexible power-down

• Low Power:

modes to save power when conversions are not

– 17 mW at 1 MSPS

being performed. The ADS8028 performance is

– Flexible Power-Down Modes

specified over the extended industrial temperature

range of –40°C to +125°C.

• SPI™-Compatible Serial Interface: 20 MHz

The ADS8028 is ideal for demanding measurement

• Small Footprint: 4-mm × 4-mm, Thin QFN-20

applications, such as sensor output monitoring,

power-supply monitoring, and printed circuit board

APPLICATIONS

(PCB) hot-spot analysis, and is available in a small

• Programmable Logic Controls (PLCs)

form-factor QFN-20 package.

• Industrial Process Controls (IPCs)

• Telecommunications

• Power-Supply Monitoring

• PCB Hot-Spot Analysis

• Battery-Powered Applications

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.

2SPI is a trademark of Motorola.

3All 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.

Summary of content (34 pages)

PAGE 1
ADS8028 www.ti.com SBAS549B – MAY 2011 – REVISED MARCH 2012 12-Bit, 1-MSPS, 8-Channel, SAR ADC with Internal Reference and Internal Temperature Sensor Check for Samples: ADS8028 FEATURES DESCRIPTION • The ADS8028 is a 12-bit analog-to-digital converter (ADC), capable of operating at sampling speeds up to 1 MSPS. The device is based on a successive approximation register (SAR) core and provides an inherent sample-and-hold (SH) front-end.
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ADS8028 SBAS549B – MAY 2011 – REVISED MARCH 2012 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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ADS8028 www.ti.com SBAS549B – MAY 2011 – REVISED MARCH 2012 ELECTRICAL CHARACTERISTICS Minimum and maximum specifications apply from TA = –40°C to +125°C. Typical specifications are at TA = +25°C. All specifications at AVDD = 2.7 V to 5.25 V, DVDD = 1.65 V to 5.25 V, fSAMPLE = 1 MHz, fSCLK = 20 MHz, and VREF = 2.5 V internal, unless otherwise noted.
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ADS8028 SBAS549B – MAY 2011 – REVISED MARCH 2012 www.ti.com ELECTRICAL CHARACTERISTICS (continued) Minimum and maximum specifications apply from TA = –40°C to +125°C. Typical specifications are at TA = +25°C. All specifications at AVDD = 2.7 V to 5.25 V, DVDD = 1.65 V to 5.25 V, fSAMPLE = 1 MHz, fSCLK = 20 MHz, and VREF = 2.5 V internal, unless otherwise noted.
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ADS8028 www.ti.com SBAS549B – MAY 2011 – REVISED MARCH 2012 ELECTRICAL CHARACTERISTICS (continued) Minimum and maximum specifications apply from TA = –40°C to +125°C. Typical specifications are at TA = +25°C. All specifications at AVDD = 2.7 V to 5.25 V, DVDD = 1.65 V to 5.25 V, fSAMPLE = 1 MHz, fSCLK = 20 MHz, and VREF = 2.5 V internal, unless otherwise noted. ADS8028 PARAMETER TEST CONDITIONS MIN TYP MAX UNIT AVDD = DVDD = 3.0 V 17 18.9 mW AVDD = DVDD = 3.6 V 20.9 22.7 mW AVDD = DVDD = 5.
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ADS8028 SBAS549B – MAY 2011 – REVISED MARCH 2012 www.ti.com PARAMETER MEASUREMENT INFORMATION TIMING CHARACTERISTICS tPH_CSZ tCONV CS tSU_CSCK SCLK 1 2 t ACQ tPH_SCLK tSCLK 3 4 5 6 13 14 15 16 tPL_SCLK tD_CKDO tDV_CSDO DOUT 3-State ADD3 ADD2 ADD1 ADD0 tSU_CKDI DIN WRITE DB11 tHT_CKDO DB10 DB2 tDZ_CKDO DB1 DB0 3-State tHT_CKDI REPEAT AIN0 AIN1 AIN2 AIN3 EXT_REF TMP_AVG STANDBY Figure 1.
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ADS8028 www.ti.com SBAS549B – MAY 2011 – REVISED MARCH 2012 PIN CONFIGURATIONS AIN2 AIN1 AIN0 PD/RST DVDD 20 19 18 17 16 RTJ PACKAGE(1) QFN-20 (TOP VIEW) AIN3 1 15 SCLK AIN4 2 14 DOUT AIN5 3 13 DIN AIN6 4 12 TM_BUSY AIN7 5 11 CS 10 AVDD 8 NC 9 7 REF DGND 6 AGND Thermal Pad (1) The exposed thermal pad on the bottom of the package must be soldered to the printed circuit board (PCB) ground for proper functionality and heat dissipation. NOTE: NC = no connection.
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ADS8028 SBAS549B – MAY 2011 – REVISED MARCH 2012 www.ti.com TYPICAL CHARACTERISTICS All plots at TA = +25°C, AVDD = 3.0 V, DVDD = 3.0 V, fSAMPLE = 1 MHz, fSCLK = 20 MHz, and VREF = 2.5 V internal, unless otherwise noted. TYPICAL FFT INL vs VREF 0 0.6 Amplitude (dB) −40 Intergral Nonlinearity (LSB) fSAMPLE = 1.176 MHz fIN = 41.68 kHz fSCLK = 20 MHz SNR = 72.7 dB THD = −93.6 dB −20 −60 −80 −100 −120 −140 0 50 0.4 0.2 0 Minimum INL −0.2 AVDD = 5 V DVDD = 5 V External Reference Mode −0.4 −0.
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ADS8028 www.ti.com SBAS549B – MAY 2011 – REVISED MARCH 2012 TYPICAL CHARACTERISTICS (continued) All plots at TA = +25°C, AVDD = 3.0 V, DVDD = 3.0 V, fSAMPLE = 1 MHz, fSCLK = 20 MHz, and VREF = 2.5 V internal, unless otherwise noted. VREF vs CURRENT LOAD SINAD vs VREF 75 Signal to Noise and Distortion (dB) 3 Reference Voltage (V) 2.5 2 1.5 1 0.5 0 −11 −9 −7 −5 −3 −1 1 3 Current Load (mA) 5 7 9 69 66 AVDD = 5 V DVDD = 5 V External Reference Mode 63 60 11 1 1.5 G007 2.5 3 3.
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ADS8028 SBAS549B – MAY 2011 – REVISED MARCH 2012 www.ti.com TYPICAL CHARACTERISTICS (continued) All plots at TA = +25°C, AVDD = 3.0 V, DVDD = 3.0 V, fSAMPLE = 1 MHz, fSCLK = 20 MHz, and VREF = 2.5 V internal, unless otherwise noted.
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ADS8028 www.ti.com SBAS549B – MAY 2011 – REVISED MARCH 2012 TYPICAL CHARACTERISTICS (continued) All plots at TA = +25°C, AVDD = 3.0 V, DVDD = 3.0 V, fSAMPLE = 1 MHz, fSCLK = 20 MHz, and VREF = 2.5 V internal, unless otherwise noted. INL vs TEMPERATURE OFFSET ERROR vs TEMPERATURE 1 4 0.6 Maximum INL 0.4 Offset Error (LSB) Integral Nonlinearity (LSB) 0.8 0.2 0 Minimum INL −0.2 −0.4 2 0 −2 −0.6 −0.8 −1 −40 −15 10 35 60 85 Free− Air Temperature (dB) −4 −40 110 125 −15 G022 Figure 20.
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ADS8028 SBAS549B – MAY 2011 – REVISED MARCH 2012 www.ti.com TYPICAL CHARACTERISTICS (continued) All plots at TA = +25°C, AVDD = 3.0 V, DVDD = 3.0 V, fSAMPLE = 1 MHz, fSCLK = 20 MHz, and VREF = 2.5 V internal, unless otherwise noted. GAIN ERROR vs AVDD 4 2 2 Gain Error (LSB) Offset Error (LSB) OFFSET ERROR vs AVDD 4 0 −2 0 −2 DVDD = 1.8 V −4 2.7 DVDD = 1.8 V 3.2 3.7 4.2 4.7 AVDD, Analog Supply Voltage (V) −4 2.7 5.2 3.2 3.7 4.2 4.7 AVDD, Analog Supply Voltage (V) G030 Figure 26.
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ADS8028 www.ti.com SBAS549B – MAY 2011 – REVISED MARCH 2012 OVERVIEW The ADS8028 is a 12-bit successive-approximation register (SAR) analog-to-digital converter (ADC) that can support throughput rates up to 1 MSPS. The device features a 2.5-V internal reference, but can also function with an external reference source. The analog input range is 0 V to VREF. The device supports eight single-ended analog inputs and integrates an internal temperature sensor.
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ADS8028 SBAS549B – MAY 2011 – REVISED MARCH 2012 www.ti.com TEMPERATURE SENSOR The internal temperature sensor measures the ADS8028 die temperature. The temperature sensor can be selected for conversion by setting the TSENSE bit in the Control Register to '1'. The TM_BUSY pin goes high as soon as the temperature sensor is selected for conversion and remains high until the conversion is completed (100 µs, max).
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ADS8028 www.ti.com SBAS549B – MAY 2011 – REVISED MARCH 2012 If the output data MSB is ‘0’, the temperature can be calculated with Equation 3: Temperature = VEXT_REF ADC_Code 10 + 109.3 - 273.15 where: VEXT_REF is the value of the external reference voltage (3) If the output data MSB is ‘1’, the temperature can be calculated with Equation 4: Temperature = VEXT_REF ADC_Code - 4096 + 109.3 - 273.15 10 where: VEXT_REF is the value of the external reference voltage (4) For a 2.
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ADS8028 SBAS549B – MAY 2011 – REVISED MARCH 2012 www.ti.com ADC TRANSFER FUNCTION The ADS8028 output is in straight binary format for all analog input channels (AIN0 to AIN7) and is in twos complement format for the temperature sensor conversion result. The transition in output code occurs at every LSB step. For the ADS8028, LSB step size is VREF/4096. The ideal ADS8028 transfer characteristic for straight binary coding is shown in Figure 32.
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ADS8028 www.ti.com SBAS549B – MAY 2011 – REVISED MARCH 2012 SERIAL INTERFACE Figure 33 shows a detailed ADS8028 serial interface timing diagram. The device uses the serial clock (SCLK) for internal conversion and for data transfer into and out of the device. The CS signal defines one frame of conversion and serial transfer. The ADS8028 samples the analog input on the CS falling edge. The sample-and-hold circuit enters into hold mode and the serial data bus comes out of 3state.
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ADS8028 SBAS549B – MAY 2011 – REVISED MARCH 2012 www.ti.com DATA WRITE OPERATION Control Register Settings The ADS8028 operation is controlled by the status of the internal Control Register. Data written into the Control Register decide the configuration of the ADS8028 for the next conversion cycle. The Control Register is 16 bits wide, and only supports write operation. The Control Register can be written to with the serial interface.
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ADS8028 www.ti.com SBAS549B – MAY 2011 – REVISED MARCH 2012 DATA READ OPERATION Table 3 shows the ADS8028 output data format. Bits ADD[3:0] specify the channel selected for conversion and bits DB[11:0] are the conversion result for the selected channel. Table 3.
PAGE 20
ADS8028 SBAS549B – MAY 2011 – REVISED MARCH 2012 www.ti.com Internal Temperature Sensor Channel The internal temperature sensor can be selected for conversion by writing a '1' to the TSENSE bit in the Control Register. On the next CS falling edge, the TM_BUSY pin goes high and remains high throughout the temperature sensor conversion process.
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ADS8028 www.ti.com SBAS549B – MAY 2011 – REVISED MARCH 2012 If multiple channels are selected by writing a '1' to all associated bits in the Control Register, the ADS8028 converts all selected channels sequentially (in ascending order) in successive frames as defined by the CS falling edges. When all selected channels in the Control Register are converted, the ADS8028 stops conversions and waits for a valid write operation to be executed in the Control Register to select the next channel to be converted.
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ADS8028 SBAS549B – MAY 2011 – REVISED MARCH 2012 www.ti.com The ADS8028 continues to operate in repeat mode until a valid write operation is executed to reprogram the Control Register. When the Control Register is updated, the ADS8028 comes out of repeat mode and begins operating as per the new programmed settings.
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ADS8028 www.ti.com SBAS549B – MAY 2011 – REVISED MARCH 2012 It takes four serial transfer cycles for the ADS8028 to exit STANDBY mode and transmit the first valid conversion data, as shown in Figure 38. The first cycle updates the STANDBY bit to '0'; the second cycle selects the channels and operation mode; the third cycle converts the selected channel; and the result of this conversion can be clocked out in the fourth cycle.
PAGE 24
ADS8028 SBAS549B – MAY 2011 – REVISED MARCH 2012 www.ti.com RESET The ADS8028 can be RESET by pulling the PD/RST pin to a logic low state for no longer than 60 ns. This input is asynchronous to the clock. On RESET, the Control Register bits are set to the default state and the temperature sensor averaging feature is reset and disabled. When the PD/RST is pulled back to a logic high state, the ADS8028 is placed in normal mode.
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ADS8028 www.ti.com SBAS549B – MAY 2011 – REVISED MARCH 2012 APPLICATION INFORMATION USAGE OF INTERNAL TEMPERATURE SENSOR The ADS8028 accurately measures and converts the temperature of its own silicon die. Most of the heat transfer between any external heat source and the ADS8028 die occurs via the thermal pad. Therefore, the ADS8028 can be used to measure the temperature of any external heat source by minimizing the thermal resistance between the heat source and the device thermal pad.
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ADS8028 SBAS549B – MAY 2011 – REVISED MARCH 2012 www.ti.com The ac performance of the circuit in Figure 40 was tested with a 2.36-VPP (–0.5 dBFS), 49.911499023-kHz input sine wave. The FFT of the sampled input signal with 8192 samples is shown in Figure 41. The high-precision input signal frequency used to achieve coherent sampling without a windowing function is applied to the data prior to the Fourier Transform.
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ADS8028 www.ti.com SBAS549B – MAY 2011 – REVISED MARCH 2012 REVISION HISTORY NOTE: Page numbers for previous revisions may differ from page numbers in the current version. Changes from Revision A (March 2012) to Revision B • Page Changed product status from Product Preview to Production Data .....................................................................................
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PACKAGE OPTION ADDENDUM www.ti.
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PACKAGE MATERIALS INFORMATION www.ti.com 14-Jul-2012 TAPE AND REEL INFORMATION *All dimensions are nominal Device Package Package Pins Type Drawing SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) B0 (mm) K0 (mm) P1 (mm) W Pin1 (mm) Quadrant ADS8028IRTJR QFN RTJ 20 3000 330.0 12.4 4.25 4.25 1.15 8.0 12.0 Q2 ADS8028IRTJT QFN RTJ 20 250 180.0 12.4 4.25 4.25 1.15 8.0 12.
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PACKAGE MATERIALS INFORMATION www.ti.com 14-Jul-2012 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) ADS8028IRTJR QFN RTJ 20 3000 367.0 367.0 35.0 ADS8028IRTJT QFN RTJ 20 250 210.0 185.0 35.
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