Datasheet AD7709 (Analog Devices)

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16-Bit - ADC with Switchable Current Sources AD7709 FEATURES APPLICATIONS 16-Bit - ADC Sensor Measurement Programmable Gain Front End Temperature Measurement Simultaneous 50 Hz and 60 Hz Rejection at 20 Hz Pressure Measurements Update Rate Weigh Scales VREF Select™ Allows Absolute and Ratiometric Portable Instrumentation Measurement Capability 4–20 mA Loops ISOURCE Select™ GENERAL DESCRIPTION 16-Bit No Missing Codes
The AD7709 is a complete analog front end for low frequency
13-Bit p-p Resolution @ 20 Hz, 20 mV Range
measurement applications. It contains a 16-bit ⌺-⌬ ADC, selectable
16-Bit p-p Resolution @ 20 Hz, 2.56 V Range
reference inputs, three switchable matched excitation current
INTERFACE
sources, low-side power switches, and a digital I/O port. The
3-Wire Serial
16-bit channel with PGA accepts fully differential, unipolar,
SPI®, QSPI™, MICROWIRE™, and DSP Compatible
and bipolar input signal ranges from 1.024 ⫻ REFIN/128 to
Schmitt Trigger on SCLK
1.024 ⫻ REFIN. It can be configured as two fully differential input channels or four pseudo-differential input channels. Signals
POWER
can be converted directly from a transducer without the need for
Specified for Single 3 V and 5 V Operation
signal conditioning.
Normal: 1.25 mA Typ @ 3 V Power-Down: 7 A (32.768 kHz Crystal Running)
The device operates from a 32.768 kHz crystal with an on-chip PLL generating the required internal operating frequency. The
ON-CHIP FUNCTIONS
output data rate from the part is software programmable. The
Rail-to-Rail Input Buffer and PGA
p-p resolution from the part varies with the programmed gain
Selectable Reference Inputs
and output data rate.
3 Switchable, Ratioed Current Sources for
The part operates from a single 3 V or 5 V supply. When
VBE Measurements
operating from 3 V supplies, the power dissipation for the part
4-Bit Digital I/O Port
is 3.75 mW. The AD7709 is housed in a 24-lead TSSOP package.
Low-Side Power Switches FUNCTIONAL BLOCK DIAGRAM REFIN1(+) REFIN2(+) REFIN1(–) REFIN2(–) XTAL1 XTAL2 VDD IEXC1 IEXC2 IEXC3 OSCILLATOR 8I 8I I AND IOUT1 PLL DOUT DIN IOUT2 I = 25 A SERIAL INTERFACE SCLK AND AIN1 CS CONTROL AIN2 LOGIC RDY BUF PGA 16-BIT - ADC AIN3/P3 MUX V RESET DD AIN4/P4 AINCOM I/O PORT AD7709 VDD GND PWRGND P1/SW1 P2/SW2
REV. A Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. No license is granted by implication or otherwise
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Document Outline FEATURES INTERFACE POWER ON-CHIP FUNCTIONS APPLICATIONS GENERAL DESCRIPTION FUNCTIONAL BLOCK DIAGRAM TABLE OF CONTENTS SPECIFICATIONS TIMING CHARACTERISTICS ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION ORDERING GUIDE PIN FUNCTION DESCRIPTIONS Typical Performance Characteristics ADC CIRCUIT INFORMATION Overview Sigma-Delta ADC NOISE PERFORMANCE ON-CHIP REGISTERS Communications Register (A1, A0 = 0, 0) Status Register (A1, A0 = 0, 0; Power-On-Reset = 00H) Configuration Register (A1, A0 = 0, 1; Power-On-Reset = 000007H) Filter Register (A1, A0 = 1, 0; Power-On-Reset = 45h) ADC Data Result Register (A1, A0 = 1, 1; Power-On-Reset = 0000h CONFIGURING THE AD7709 DIGITAL INTERFACE MICROCOMPUTER/MICROPROCESSOR INTERFACING AD7709-to-68HC11 Interface AD7709-to-8051 Interface AD7709-to-ADSP-2103/ADSP-2105 Interface CIRCUIT DESCRIPTION Analog Input Channels Programmable Gain Amplifier Bipolar/Unipolar Configuration Data Output Coding Excitation Currents Crystal Oscillator Reference Input Reset Input Power-Down Mode Grounding and Layout APPLICATIONS Pressure Measurement Temperature Measurement 3-Wire RTD Configurations Smart Transmitters OUTLINE DIMENSIONS Revision History