Datasheet

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

SPI

AV DD DVDD

GND

AIN0P

AIN1P

AIN0N

AIN1N

PDEN

SAR

ADC

SCLK

SDO

REFGNDREF

CHSEL

MUX

S/H

ADS7947

ADS7948

ADS7949

www.ti.com

SLAS708 –SEPTEMBER 2010

12/10/8-Bit, 2MSPS, Dual-Channel, Unipolar, Pseudo-Differential, Ultralow-Power

SAR Analog-to-Digital Converters

Check for Samples: ADS7947 , ADS7948, ADS7949

FEATURES

DESCRIPTION

• Sample Rate: 2MSPS

The ADS7947/8/9 are 12-bit, 10-bit, and 8-bit 2MSPS

analog-to-digital converters (ADCs), respectively.

• Pin-Compatible Family: 12/10/8-Bit

Devices operate at 2MSPS sample rate with a

• Outstanding Performance:

standard 16 clock data frame. In addition, it is

– No Missing Codes

possible to operate the ADS7947 (12-bit) at

– INL: 1LSB (max) 2.1MSPS, the ADS7948 (10-bit) at 2.57MSPS, and

the ADS7949 (8-bit) at 3MSPS with a short data

– SNR: 72dB (min)

frame optimized for the number of clocks sufficient for

• Low Power:

conversion with no drop in performance. The devices

– 7.5mW at 2MSPS Operation

feature both outstanding dc precision and excellent

dynamic performance, this family of pin-compatible

– Auto Power-Down at Lower Speeds:

devices includes a two-channel input multiplexer and

– 3.8mW at 500kSPS

a low-power successive approximation register (SAR)

– 0.8mW at 100kSPS

ADC with an inherent sample-and-hold (S/H) input

stage.

– 0.16mW at 20kSPS

• Wide Supply Range:

The ADS7947/8/9 support a wide analog supply

range that allows the full-scale input range to extend

– Analog: 2.7V to 5.5V

to 5V. A simple SPI™, with a digital supply that can

– Digital: 1.65V to AVDD

operate as low as 1.65V, allows for easy interfacing

• Simple Serial Interface (SPI)

to a wide variety of digital controllers. Automatic

power-down can be enabled when operating at

• Fully Specified from –40°C to +125°C

slower speeds to dramatically reduce power

• Tiny Footprint: 3mm × 3mm QFN

consumption.

Offered in a tiny 3mm × 3mm QFN package, the

APPLICATIONS

ADS7947/8/9 are fully specified over the extended

• Communication Systems

temperature range of –40°C to +125°C and are

• Optical Networking

suitable for a wide variety of data acquisition

• Medical Instrumentation

applications where high performance, low power, and

• Battery-Powered Equipment

small size are key.

• Data Acquisition Systems

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 (38 pages)

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ADS7947 ADS7948 ADS7949 www.ti.com SLAS708 – SEPTEMBER 2010 12/10/8-Bit, 2MSPS, Dual-Channel, Unipolar, Pseudo-Differential, Ultralow-Power SAR Analog-to-Digital Converters Check for Samples: ADS7947 , ADS7948, ADS7949 FEATURES DESCRIPTION • • • The ADS7947/8/9 are 12-bit, 10-bit, and 8-bit 2MSPS analog-to-digital converters (ADCs), respectively. Devices operate at 2MSPS sample rate with a standard 16 clock data frame. In addition, it is possible to operate the ADS7947 (12-bit) at 2.
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ADS7947 ADS7948 ADS7949 SLAS708 – SEPTEMBER 2010 www.ti.com These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam during storage or handling to prevent electrostatic damage to the MOS gates.
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ADS7947 ADS7948 ADS7949 www.ti.com SLAS708 – SEPTEMBER 2010 ELECTRICAL CHARACTERISTICS: ADS7947 (12-Bit) Minimum/maximum specifications at AVDD = 2.7V to 5.5V, DVDD = 1.65V to AVDD, TA = –40°C to +125°C, and fSAMPLE = 2MSPS, unless otherwise noted. Typical specifications at AVDD = 3V, DVDD = 1.8V, TA = +25°C, and fSAMPLE = 2MSPS. PARAMETER TEST CONDITIONS MIN TYP MAX UNITS ANALOG INPUT Full-scale input span (1) AINxP – AINxN Absolute input range 0 VREF V AIN0P, AIN1P –0.2 AVDD + 0.
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ADS7947 ADS7948 ADS7949 SLAS708 – SEPTEMBER 2010 www.ti.com ELECTRICAL CHARACTERISTICS: ADS7947 (12-Bit) (continued) Minimum/maximum specifications at AVDD = 2.7V to 5.5V, DVDD = 1.65V to AVDD, TA = –40°C to +125°C, and fSAMPLE = 2MSPS, unless otherwise noted. Typical specifications at AVDD = 3V, DVDD = 1.8V, TA = +25°C, and fSAMPLE = 2MSPS. PARAMETER TEST CONDITIONS MIN TYP MAX UNITS AVDD 2.7 3.3 5.5 V DVDD 1.65 3.
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ADS7947 ADS7948 ADS7949 www.ti.com SLAS708 – SEPTEMBER 2010 ELECTRICAL CHARACTERISTICS: ADS7948 (10-Bit) Minimum/maximum specifications at AVDD = 2.7V to 5.5V, DVDD = 1.65V to AVDD, TA = –40°C to +125°C, and fSAMPLE = 2MSPS, unless otherwise noted. Typical specifications at AVDD = 3V, DVDD = 1.8V, TA = +25°C, and fSAMPLE = 2MSPS. PARAMETER TEST CONDITIONS MIN TYP MAX UNITS ANALOG INPUT Full-scale input span (1) AINxP – AINxN Absolute input range 0 VREF V AIN0P, AIN1P –0.2 AVDD + 0.
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ADS7947 ADS7948 ADS7949 SLAS708 – SEPTEMBER 2010 www.ti.com ELECTRICAL CHARACTERISTICS: ADS7948 (10-Bit) (continued) Minimum/maximum specifications at AVDD = 2.7V to 5.5V, DVDD = 1.65V to AVDD, TA = –40°C to +125°C, and fSAMPLE = 2MSPS, unless otherwise noted. Typical specifications at AVDD = 3V, DVDD = 1.8V, TA = +25°C, and fSAMPLE = 2MSPS. PARAMETER TEST CONDITIONS MIN TYP MAX UNITS AVDD 2.7 3.3 5.5 V DVDD 1.65 3.
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ADS7947 ADS7948 ADS7949 www.ti.com SLAS708 – SEPTEMBER 2010 ELECTRICAL CHARACTERISTICS: ADS7949 (8-Bit) Minimum/maximum specifications at AVDD = 2.7V to 5.5V, DVDD = 1.65V to AVDD, TA = –40°C to +125°C, and fSAMPLE = 2MSPS, unless otherwise noted. Typical specifications at AVDD = 3V, DVDD = 1.8V, TA = +25°C, and fSAMPLE = 2MSPS. PARAMETER TEST CONDITIONS MIN TYP MAX UNITS ANALOG INPUT Full-scale input span (1) AINxP – AINxN Absolute input range 0 VREF V AIN0P, AIN1P –0.2 AVDD + 0.
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ADS7947 ADS7948 ADS7949 SLAS708 – SEPTEMBER 2010 www.ti.com ELECTRICAL CHARACTERISTICS: ADS7949 (8-Bit) (continued) Minimum/maximum specifications at AVDD = 2.7V to 5.5V, DVDD = 1.65V to AVDD, TA = –40°C to +125°C, and fSAMPLE = 2MSPS, unless otherwise noted. Typical specifications at AVDD = 3V, DVDD = 1.8V, TA = +25°C, and fSAMPLE = 2MSPS. PARAMETER TEST CONDITIONS MIN TYP MAX UNITS AVDD 2.7 3.3 5.5 V DVDD 1.65 3.
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ADS7947 ADS7948 ADS7949 www.ti.com SLAS708 – SEPTEMBER 2010 TIMING DIAGRAM Sample N Sample N+1 1/fSAMPLE tACQ tCONV CS tSU1 SCLK 1 tWH 2 3 tD1 SDO D11 4 5 6 7 D9 8 9 10 tW1 tD4 11 12 13 14 15 16 tD3 tD2 tH1 D10 tWL D8 D7 D6 D5 D4 D3 D2 D1 D0 Data from Sample N-1 TIMING REQUIREMENTS All specifications at DVDD = 1.65V to AVDD and TA = –40°C to +125°C, unless otherwise noted. TEST CONDITIONS (1) PARAMETER tCONV tACQ Conversion time MAX UNIT ADS7947 (12-bit) 13.
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ADS7947 ADS7948 ADS7949 SLAS708 – SEPTEMBER 2010 www.ti.com PIN CONFIGURATION DVDD SDO SCLK CS 16 15 14 13 RTE PACKAGE QFN-16 (TOP VIEW) REF 3 10 NC REFGND 4 9 NC 8 CH SEL AIN1P 11 7 2 AIN1N AVDD 6 PDEN AIN0N 12 5 1 AIN0P GND PIN FUNCTIONS PIN NO.
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ADS7947 ADS7948 ADS7949 www.ti.com SLAS708 – SEPTEMBER 2010 TYPICAL CHARACTERISTICS: ADS7947, ADS7948, ADS7949 At TA = +25°C, DVDD = 1.8V, VREF = 2.5V, and fSAMPLE = 2MSPS, unless otherwise noted. SUPPLY CURRENT vs ANALOG SUPPLY VOLTAGE SUPPLY CURRENT vs TEMPERATURE 3.2 2.4 AVDD = 3V 2.38 Supply Current (mA) Supply Current (mA) 3 2.8 2.6 2.4 2.36 2.34 2.32 2.2 2 2.3 2.7 3.2 3.7 4.2 4.7 5.7 5.
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ADS7947 ADS7948 ADS7949 SLAS708 – SEPTEMBER 2010 www.ti.com TYPICAL CHARACTERISTICS: ADS7947 (12-Bit) At TA = +25°C, DVDD = 1.8V, VREF = 2.5V, and fSAMPLE = 2MSPS, unless otherwise noted. INTEGRAL LINEARITY vs ANALOG SUPPLY VOLTAGE 1 1 0.8 0.8 0.6 0.6 0.4 Integral Linearity (LSBs) Differential Linearity (LSBs) DIFFERENTIAL LINEARITY vs ANALOG SUPPLY VOLTAGE Maximum DNL 0.2 0 -0.2 Minimum DNL -0.4 -0.6 -0.8 -1 Maximum INL 0.4 0.2 0 -0.2 Minimum INL -0.4 -0.6 -0.8 2.7 3.2 3.7 4.2 4.
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ADS7947 ADS7948 ADS7949 www.ti.com SLAS708 – SEPTEMBER 2010 TYPICAL CHARACTERISTICS: ADS7947 (12-Bit) (continued) At TA = +25°C, DVDD = 1.8V, VREF = 2.5V, and fSAMPLE = 2MSPS, unless otherwise noted. OFFSET ERROR vs TEMPERATURE 1 0.8 0.8 0.6 0.6 Offset Error (LSBs) Offset Error (LSBs) OFFSET ERROR vs ANALOG SUPPLY VOLTAGE 1 0.4 0.2 0 -0.2 -0.4 0.4 0.2 0 -0.2 -0.4 -0.6 -0.6 -0.8 -0.8 -1 2.7 3.2 3.7 4.2 4.7 -1 5.7 5.
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ADS7947 ADS7948 ADS7949 SLAS708 – SEPTEMBER 2010 www.ti.com TYPICAL CHARACTERISTICS: ADS7947 (12-Bit) (continued) At TA = +25°C, DVDD = 1.8V, VREF = 2.5V, and fSAMPLE = 2MSPS, unless otherwise noted. SNR vs ANALOG SUPPLY VOLTAGE fIN = 2kHz AVDD = 3V fIN = 2kHz 73.8 Signal-to-Noise Ratio (dB) 73.8 Signal-to-Noise Ratio (dB) SNR vs TEMPERATURE 74 74 73.6 73.4 73.2 73 72.8 72.6 72.4 73.6 73.4 73.2 73 72.8 72.6 72.4 72.2 72.2 72 72 2.7 3.2 3.7 4.7 4.2 5.2 5.
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ADS7947 ADS7948 ADS7949 www.ti.com SLAS708 – SEPTEMBER 2010 TYPICAL CHARACTERISTICS: ADS7947 (12-Bit) (continued) At TA = +25°C, DVDD = 1.8V, VREF = 2.5V, and fSAMPLE = 2MSPS, unless otherwise noted. SINAD vs REFERENCE VOLTAGE SINAD vs INPUT FREQUENCY 74 AVDD = 5V fIN = 2kHz 73.8 Signal-to-Noise and Distortion (dB) Signal-to-Noise and Distortion (dB) 74 73.6 73.4 73.2 73 72.8 72.6 72.4 72.2 72 AVDD = 3V Throughput = 2MSPS 73.8 73.6 73.4 73.2 73 72.8 72.6 72.4 72.2 72 2.5 3.5 3 4.
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ADS7947 ADS7948 ADS7949 SLAS708 – SEPTEMBER 2010 www.ti.com TYPICAL CHARACTERISTICS: ADS7947 (12-Bit) (continued) At TA = +25°C, DVDD = 1.8V, VREF = 2.5V, and fSAMPLE = 2MSPS, unless otherwise noted. SFDR vs AVDD SFDR vs TEMPERATURE -87.75 fIN = 2kHz -87 Total Harmonic Distortion (dB) Total Harmonic Distortion (dB) -86.8 -87.2 -87.4 -87.6 -87.8 -88 -88.2 AVDD = 3V fIN = 2kHz -87.8 -87.85 -87.9 -87.95 -88 -88.05 -88.1 -88.4 2.7 3.7 3.2 4.2 4.7 5.2 5.
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ADS7947 ADS7948 ADS7949 www.ti.com SLAS708 – SEPTEMBER 2010 TYPICAL CHARACTERISTICS: ADS7947 (12-Bit) (continued) At TA = +25°C, DVDD = 1.8V, VREF = 2.5V, and fSAMPLE = 2MSPS, unless otherwise noted. TYPICAL DNL 1 0.6 0.6 DNL (LSBs) INL (LSBs) TYPICAL INL 1 0.2 -0.2 -0.6 -1 0.2 -0.2 -0.6 0 512 1024 1536 2048 2560 3072 3584 4096 -1 0 512 1024 1536 2048 2560 Output Code Output Code Figure 36. Figure 37.
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ADS7947 ADS7948 ADS7949 SLAS708 – SEPTEMBER 2010 www.ti.com OVERVIEW The ADS7947 is 12-bit, miniature, dual-channel, low-power SAR ADC. The ADS7948 and ADS7949 are 10-bit and 8-bit devices, respectively, from the same product family. These devices feature very low power consumption at rated speed. The PDEN pin enables an auto power-down mode that further reduces power consumption at lower speeds.
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ADS7947 ADS7948 ADS7949 www.ti.com SLAS708 – SEPTEMBER 2010 Figure 39 shows an equivalent circuit of the multiplexer and ADC sampling stage. The positive and negative inputs are separately sampled on 32pF sampling capacitorss. The multiplexer and sampling switches are represented by an ideal switch in series with a 12Ω resistance. During sampling, the devices connect the 32pF sampling capacitor to the ADC driver. This connection creates a glitch at the device input.
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ADS7947 ADS7948 ADS7949 SLAS708 – SEPTEMBER 2010 www.ti.com REFERENCE The ADS7947/8/9 use an external reference voltage during the conversion of a sampled signal. The devices switch the capacitors used in the conversion process to the reference terminal during conversion. The switching frequency is the same as the SCLK frequency. It is necessary to decouple the REF terminal to REFGND with a 1µF ceramic capacitor in order to get the best noise performance from the device.
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ADS7947 ADS7948 ADS7949 www.ti.com SLAS708 – SEPTEMBER 2010 ADC TRANSFER FUNCTION The ADS7947 (12-bit), ADS7948 (10-bit), and ADS7949 (8-bit) devices are unipolar, pseudo-differential input. The ADC output is in straight binary format. Figure 42 shows ideal characteristics for this family of devices. Here, FSR is the full-scale range for the ADC input (AINxP – AINxN) and is equal to the reference input voltage to the ADC (VREF).
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ADS7947 ADS7948 ADS7949 SLAS708 – SEPTEMBER 2010 www.ti.com DEVICE OPERATION The ADS7947/8/9 are typically operated with either a 16-clock frame or 32-clock frame for ease of interfacing with the host processor. 16-CLOCK FRAME Figure 43 through Figure 45 show the devices operating in 16-clock mode. This mode is the fastest mode for device operation. In this mode, the devices output data from previous conversions while converting the recently sampled signal.
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ADS7947 ADS7948 ADS7949 www.ti.com SLAS708 – SEPTEMBER 2010 Figure 44 and Figure 45 show the 16-clock mode operation for the ADS7948 and ADS7949, respectively. The operation for these 10-bit and 8-bit devices is identical to the ADS7947 except that the conversion ends on different edges of SCLK. For the ADS7948, the conversion ends and acquisition starts on the 11th SCLK rising edge. For the ADS7949, the device uses the ninth SCLK rising edge for the conversion end and acquisition start.
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ADS7947 ADS7948 ADS7949 SLAS708 – SEPTEMBER 2010 www.ti.com 32-CLOCK FRAME Figure 46 through Figure 48 show the devices operating in 32-clock mode. In this mode, the devices convert and output the data from the most recent sample before taking the next sample. Sample N Sample N+1 tACQ tCONV CS 1 SCLK 2 14 15 16 17 D11 SDO 18 23 24 25 26 27 28 D10 D5 D4 D3 D2 D1 D0 29 30 31 32 Data from Sample N Figure 46.
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ADS7947 ADS7948 ADS7949 www.ti.com SLAS708 – SEPTEMBER 2010 CS can be held low past the 16th falling edge of SCLK. The device continues to output recently converted data starting with the 16th SCLK falling edge. If CS is held low until the 30th SCLK falling edge, then the device detects 32-clock mode. Note that the device data from recent conversions are already out with no latency before the 30th SCLK falling edge.
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ADS7947 ADS7948 ADS7949 SLAS708 – SEPTEMBER 2010 www.ti.com tPDSU tPDH PDEN Sample N-1 Dummy Sample Sample N CS SCLK 1 15 2 16 1 2 15 16 1 11 2 12 13 14 15 16 SDO Data from Sample N-2 Data from Sample N-1 Data from Sample N Power-Down State (Internal) Active Power-Down Figure 50. Entry Into Power-Down with 16-Clock Burst Mode As shown in Figure 50, the two frames capturing the N–1 and Nth samples are normal 16-clock frames.
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ADS7947 ADS7948 ADS7949 www.ti.com SLAS708 – SEPTEMBER 2010 APPLICATION INFORMATION The device employs a sample-and-hold stage at the input; see Figure 39 for a typical equivalent circuit of a sample-and-hold stage. The device connects a 32pF sampling capacitor during sampling. This configuration results in a glitch at the input terminals of the device at the start of the sample.
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ADS7947 ADS7948 ADS7949 SLAS708 – SEPTEMBER 2010 www.ti.com DRIVING AN ADC WITHOUT A DRIVING OP AMP There are some low input signal bandwidth applications, such as battery power monitoring or mains monitoring. For these applications, it is not required to operate an ADC at high sampling rates and it is desirable to avoid using a driving op amp from a cost perspective. In this case, the ADC input sees the impedance of the signal source (such as a battery or mains transformer).
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ADS7947 ADS7948 ADS7949 www.ti.com SLAS708 – SEPTEMBER 2010 The device sampling rate can be maximized by using a 34MHz clock even for lower throughputs. Table 2 shows typical calculations for the ADS7947(12-bit). Table 2.
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ADS7947 ADS7948 ADS7949 SLAS708 – SEPTEMBER 2010 www.ti.com A common ground plane for both analog and digital often gives better results. Typically, the second PCB layer is the ground plane. The ADC ground pins are returned to the ground plane through multiple vias (PTH). It is a good practice to place analog components on one side and digital components on other side of the ADC (or ADCs). All signals must be routed, assuming there is a split ground plane for analog and digital.
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PACKAGE OPTION ADDENDUM www.ti.
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PACKAGE OPTION ADDENDUM www.ti.com 11-Apr-2013 Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties.
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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 ADS7947SRTER WQFN RTE 16 SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) B0 (mm) K0 (mm) P1 (mm) W Pin1 (mm) Quadrant 3000 330.0 12.4 3.3 3.3 1.1 8.0 12.0 Q2 ADS7947SRTET WQFN RTE 16 250 180.0 12.4 3.3 3.3 1.1 8.0 12.0 Q2 ADS7948SRTER WQFN RTE 16 3000 330.0 12.4 3.3 3.3 1.1 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) ADS7947SRTER WQFN RTE 16 3000 367.0 367.0 35.0 ADS7947SRTET WQFN RTE 16 250 210.0 185.0 35.0 ADS7948SRTER WQFN RTE 16 3000 367.0 367.0 35.0 ADS7948SRTET WQFN RTE 16 250 210.0 185.0 35.0 ADS7949SRTER WQFN RTE 16 3000 367.0 367.0 35.0 ADS7949SRTET WQFN RTE 16 250 210.0 185.0 35.
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