Datasheet

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

12-Bit, 4-Channel Serial Output Sampling

ANALOG-TO-DIGITAL CONVERTER

FEATURES

● SINGLE SUPPLY: 2.7V to 5V

● 4-CHANNEL SINGLE-ENDED OR

2-CHANNEL DIFFERENTIAL INPUT

● UP TO 200kHz CONVERSION RATE

● ±1LSB MAX INL AND DNL

● NO MISSING CODES

● 72dB SINAD

● SERIAL INTERFACE

● DIP-16 OR SSOP-16 PACKAGE

● ALTERNATE SOURCE FOR MAX1247

● ADS7841ES: +125°C Version

DESCRIPTION

The ADS7841 is a 4-channel, 12-bit sampling Analog-to-

Digital Converter (ADC) with a synchronous serial inter-

face. The resolution is programmable to either 8 bits or 12

bits. Typical power dissipation is 2mW at a 200kHz through-

put rate and a +5V supply. The reference voltage (V

REF

) can

be varied between 100mV and V

, providing a correspond-

ing input voltage range of 0V to V

REF

. The device includes

a shutdown mode which reduces power dissipation to under

15µW. The ADS7841 is tested down to 2.7V operation.

Low power, high speed, and on-board multiplexer make the

ADS7841 ideal for battery-operated systems such as per-

sonal digital assistants, portable multi-channel data loggers,

and measurement equipment. The serial interface also pro-

vides low-cost isolation for remote data acquisition. The

ADS7841 is available in a DIP-16 or a SSOP-16 package

and is specified over the –40°C to +125°C

(1)

temperature

range.

NOTE: (1) ES grade only.

CDAC

SAR

Comparator

Four

Channel

Multiplexer

Serial

Interface

and

Control

CH0

CH1

CH2

CH3

COM

REF

SHDN

DIN

DOUT

MODE

BUSY

DCLK

ADS7841

APPLICATIONS

● DATA ACQUISITION

● TEST AND MEASUREMENT

● INDUSTRIAL PROCESS CONTROL

● PERSONAL DIGITAL ASSISTANTS

● BATTERY-POWERED SYSTEMS

ADS7841

SBAS084B – JULY 2001

www.ti.com

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.

PRODUCTION DATA information is current as of publication date.

Products conform to specifications per the terms of Texas Instruments

standard warranty. Production processing does not necessarily include

testing of all parameters.

Summary of content (19 pages)

PAGE 1
ADS7841 ADS 784 ADS 784 1 1 SBAS084B – JULY 2001 12-Bit, 4-Channel Serial Output Sampling ANALOG-TO-DIGITAL CONVERTER FEATURES DESCRIPTION ● SINGLE SUPPLY: 2.7V to 5V The ADS7841 is a 4-channel, 12-bit sampling Analog-toDigital Converter (ADC) with a synchronous serial interface. The resolution is programmable to either 8 bits or 12 bits. Typical power dissipation is 2mW at a 200kHz throughput rate and a +5V supply.
PAGE 2
ELECTROSTATIC DISCHARGE SENSITIVITY ABSOLUTE MAXIMUM RATINGS(1) +VCC to GND ........................................................................ –0.3V to +6V Analog Inputs to GND ............................................ –0.3V to +VCC + 0.3V Digital Inputs to GND ........................................................... –0.3V to +6V Power Dissipation .......................................................................... 250mW Maximum Junction Temperature .......................................
PAGE 3
ELECTRICAL CHARACTERISTICS: +5V At TA = TMIN to TMAX, +VCC = +5V, VREF = +5V, fSAMPLE = 200kHz, and fCLK = 16 • fSAMPLE = 3.2MHz, unless otherwise noted. ADS7841E, P PARAMETER ANALOG INPUT Full-Scale Input Span Absolute Input Range CONDITIONS MIN Positive Input - Negative Input 0 Positive Input –0.2 Negative Input –0.2 Capacitance Leakage Current VREF +VCC +0.2 +1.25 ✻ ✻ ✻ TYP ±2 ✻ ✻ ✻ ✻ 68 72 0.1 DCLK Static 70 76 +VCC 5 40 2.5 0.001 3.0 –0.3 3.
PAGE 4
ELECTRICAL CHARACTERISTICS: +2.7V At TA = –40°C to +85°C, +VCC = +2.7V, VREF = +2.5V, fSAMPLE = 125kHz, and fCLK = 16 • fSAMPLE = 2MHz, unless otherwise noted. ADS7841E, P PARAMETER ANALOG INPUT Full-Scale Input Span Absolute Input Range CONDITIONS MIN Positive Input - Negative Input Positive Input Negative Input 0 –0.2 –0.2 TYP Capacitance Leakage Current POWER SUPPLY REQUIREMENTS +VCC Quiescent Current ✻ ✻ ✻ TYP 0.15 0.1 30 70 ±2 ±0.5 ±3 1.0 ±4 1.
PAGE 5
TYPICAL CHARACTERISTICS: +5V At TA = +25°C, +VCC = +5V, VREF = +5V, fSAMPLE = 200kHz, and fCLK = 16 • fSAMPLE = 3.2MHz, unless otherwise noted. FREQUENCY SPECTRUM (4096 Point FFT; fIN = 10.3kHz, –0.2dB) 0 0 –20 –20 –40 –40 Amplitude (dB) Amplitude (dB) FREQUENCY SPECTRUM (4096 Point FFT; fIN = 1,123Hz, –0.
PAGE 6
TYPICAL CHARACTERISTICS: +2.7V At TA = +25°C, +VCC = +2.7V, VREF = +2.5V, fSAMPLE = 125kHz, and fCLK = 16 • fSAMPLE = 2MHz, unless otherwise noted. FREQUENCY SPECTRUM (4096 Point FFT; fIN = 10.6kHz, –0.2dB) 0 0 –20 –20 –40 –40 Amplitude (dB) –60 –80 –100 –80 –100 –120 –120 0 15.6 31.3 46.9 62.5 0 15.6 31.3 46.9 62.
PAGE 7
TYPICAL CHARACTERISTICS: +2.7V (Cont.) At TA = +25°C, +VCC = +2.7V, VREF = +2.5V, fSAMPLE = 125kHz, and fCLK = 16 • fSAMPLE = 2MHz, unless otherwise noted. POWER DOWN SUPPLY CURRENT vs TEMPERATURE 400 140 350 120 Supply Current (nA) Supply Current (µA) SUPPLY CURRENT vs TEMPERATURE 300 250 200 150 100 80 60 40 100 20 –40 –20 0 20 40 60 80 100 –40 –20 0 40 60 80 100 DIFFERENTIAL LINEARITY ERROR vs CODE 1.00 1.00 0.75 0.75 0.50 0.
PAGE 8
TYPICAL CHARACTERISTICS: +2.7V (Cont.) At TA = +25°C, +VCC = +2.7V, VREF = +2.5V, fSAMPLE = 125kHz, and fCLK = 16 • fSAMPLE = 2MHz, unless otherwise noted.
PAGE 9
THEORY OF OPERATION The input current on the analog inputs depends on the conversion rate of the device. During the sample period, the source must charge the internal sampling capacitor (typically 25pF). After the capacitor has been fully charged, there is no further input current. The rate of charge transfer from the analog source to the converter is a function of conversion rate. The ADS7841 is a classic Successive Approximation Register (SAR) ADC.
PAGE 10
REFERENCE INPUT The voltage into the VREF input is not buffered and directly drives the Capacitor Digital-to-Analog Converter (CDAC) portion of the ADS7841. Typically, the input current is 13µA with a 2.5V reference. This value will vary by microamps depending on the result of the conversion. The reference current diminishes directly with both conversion rate and reference voltage.
PAGE 11
Control Byte MODE pin is HIGH, then the MODE bit determines the number of bits for each conversion, either 12 bits (LOW) or 8 bits (HIGH). Also shown in Figure 3 is the placement and order of the control bits within the control byte. Tables III and IV give detailed information about these bits. The first bit, the ‘S’ bit, must always be HIGH and indicates the start of the control byte. The ADS7841 will ignore inputs on the DIN pin until the start bit is detected.
PAGE 12
Digital Timing microcontrollers and digital signal processors as they are generally not capable of providing 15 clock cycles per serial transfer. However, this method could be used with Field Programmable Gate Arrays (FPGAs) or Application Specific Integrated Circuits (ASICs). Note that this effectively increases the maximum conversion rate of the converter beyond the values given in the specification tables, which assume 16 clock cycles per conversion.
PAGE 13
Data Format The ADS7841 output data is in straight binary format, as shown in Figure 7. This figure shows the ideal output code for the given input voltage and does not include the effects of offset, gain, or noise. FS = Full-Scale Voltage = VREF 1LSB = VREF/4096 1LSB 11...111 Output Code 11...110 11...101 gible. If the conversion rate is decreased by simply slowing the frequency of the DCLK input, the two modes remain approximately equal.
PAGE 14
LAYOUT For optimum performance, care should be taken with the physical layout of the ADS7841 circuitry. This is particularly true if the reference voltage is low and/or the conversion rate is high. The basic SAR architecture is sensitive to glitches or sudden changes on the power supply, reference, ground connections, and digital inputs that occur just prior to latching the output of the analog comparator.
PAGE 15
PACKAGE OPTION ADDENDUM www.ti.
PAGE 16
PACKAGE OPTION ADDENDUM www.ti.com 6-Jul-2009 (3) MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature. 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.
PAGE 17
PACKAGE MATERIALS INFORMATION www.ti.com 21-Mar-2008 TAPE AND REEL INFORMATION *All dimensions are nominal Device Package Package Pins Type Drawing SPQ Reel Reel Diameter Width (mm) W1 (mm) A0 (mm) B0 (mm) K0 (mm) P1 (mm) W Pin1 (mm) Quadrant ADS7841E/2K5 SSOP/ QSOP DBQ 16 2500 330.0 12.4 6.4 5.2 2.1 8.0 12.0 Q1 ADS7841EB/2K5 SSOP/ QSOP DBQ 16 2500 330.0 12.4 6.4 5.2 2.1 8.0 12.
PAGE 18
PACKAGE MATERIALS INFORMATION www.ti.com 21-Mar-2008 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) ADS7841E/2K5 SSOP/QSOP DBQ 16 2500 346.0 346.0 29.0 ADS7841EB/2K5 SSOP/QSOP DBQ 16 2500 346.0 346.0 29.
PAGE 19
IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications, enhancements, improvements, and other changes to its products and services at any time and to discontinue any product or service without notice. Customers should obtain the latest relevant information before placing orders and should verify that such information is current and complete.