Analog Devices’ AD7193 is a quad 4.8kHz ultralow noise 24-bit Sigma-Delta ADC with PGA, RMS noise of 11 nV @ 4.7 Hz (gain = 128), offset drift of ±5 nV/°C, gain drift of ±1 ppm/℃, working voltage 3V-5.25V, mainly used in PLC/DCS analog input Module, data acquisition and stress gauge sensor. This article presents the AD7193 main features, functional block diagram, basic connection block diagram, typical application circuit diagram for a flow meter, and a simplified circuit diagram of a fully programmed universal analog front end (CN0209) for process control applications and the EVAL-CN0209-SDPZ evaluation board circuit diagram, bill of materials, and PCB Layout.

The AD7193 is a low noise, complete analog front end for high precision measurement applications. It contains a low noise, 24-bit sigma-delta (Σ-Δ) analog-to-digital converter (ADC). The on-chip low noise gain stage means that signals of small amplitude can interface directly to the ADC.

The device can be configured to have four differential inputs or eight pseudo differential inputs. The on-chip channel sequencer allows several channels to be enabled simultaneously, and the AD7193 sequentially converts on each enabled channel, simplifying communication with the part. The on-chip 4.92 MHz clock can be used as the clock source to the ADC or, alternatively, an external clock or crystal can be used. The output data rate from the part can be varied from 4.7 Hz to 4.8 kHz.

The device has a very flexible digital filter, including a fast settling option. Variables such as output data rate and settling time are dependent on the option selected. The AD7193 also includes a zero latency option.

The part operates with a power supply from 3 V to 5.25 V. It consumes a current of 4.65 mA, and it is available in a 28-lead TSSOP package and a 32-lead LFCSP package.

AD7193 main features:

Fast settling filter option

4 differential/8 pseudo differential input channels

RMS noise: 11 nV @ 4.7 Hz (gain = 128)

15.5 noise-free bits @ 2.4 kHz (gain = 128)

Up to 22 noise-free bits (gain = 1)

Offset drift: ±5 nV/℃

Gain drift: ±1 ppm/℃

Specified drift over time

Automatic channel sequencer

Programmable gain (1 to 128)

Output data rate: 4.7 Hz to 4.8 kHz

Internal or external clock

Simultaneous 50 Hz/60 Hz rejection

4 general-purpose digital outputs

Power supply

AVDD: 3V to 5.25V

DVDD: 2.7V to 5.25V

Current: 4.65 mA

Temperature range: −40℃ to +105℃

28-lead TSSOP and 32-lead LFCSP packages

Interface

3-wire serial

SPI, QSPI™, MICROWIRE™, and DSP compatible

Schmitt trigger on SCLK

AD7193 application:

PLC/DCS analog input modules

Data acquisition

Strain gage transducers

figure 1. AD7193 functional block diagram

figure 2. AD7193 basic connection diagram

image 3. AD7193 Typical Application Circuit Diagram (Flowmeter)

Fully Programmable Universal Analog Front End for Process Control Applications (CN0209) EVAL-CN0209-SDPZ

This circuit uses the EVAL-CN0209-SDPZ circuit board and the EVAL-SDP-CB1Z System Demonstration Platform (SDP) evaluation board. The two boards have 120-pin mating connectors, allowing for the quick setup and evaluation of the circuit’s performance. The The EVAL-CN0209-SDPZ board contains the circuit to be evaluated, as described in this note, and the SDP evaluation board is used with the CN0209 evaluation software to capture the data from the EVAL-CN0209-SDPZ circuit board.

Equipment Needed

PC with a USB port and Windows® XP or Windows Vista® (32-bit) or Windows® 7 (32-bit)

EVAL-CN0209-SDPZ Circuit Evaluation Board

EVAL-SDP-CB1Z SDP Evaluation Board

CN0209 Evaluation Software

Power supply: +15 V and –15 V

RTD temperature sensor

Thermocouple

The EVAL-CN0209-SDPZ evaluation board includes:

The EVAL-CN0209-SDPZ evaluation kit includes self-installing software on CD. The software is compatible with Windows® XP, Windows Vista (32-bits) and Windows 7 (32-bits).

The circuit shown in Figure 1 provides a fully programmable universal analog front end (AFE) for process control applications. The following inputs are supported: 2-, 3-, and 4- wire RTD configurations, thermocouple inputs with cold junction compensation, unipolar and bipolar input voltages, and 4 mA-to-20 mA inputs.

Today, many analog input modules use wire links (jumpers) to configure the customer input requirements. This requires time, knowledge, and manual intervention to configure and reconfigure the input. This circuit provides a software controllable switch to configure the modes along with a constant current source to excite the RTD. The circuit is also reconfigurable to set common-mode voltages for the thermocouple configuration. A differential amplifier is used to condition the analog input voltage range to the Σ-Δ ADC. The circuit provides industry-leading performance and cost. Because of the voltage gain provided by the AD8676 and AD8275, the design is particularly suitable for small signal inputs, all types of RTDs, or thermocouples.

The AD7193 is a 24-bit Σ-Δ ADC that can be configured to have four differential inputs or eight pseudo differential inputs. The ADuM1400 and ADuM1401 provide all the necessary signal isolation between the microcontroller and the ADC. The circuit also includes standard external protection and is compliant with the IEC 61000 specifications.

Main applications of EVAL-CN0209-SDPZ:

能源

Motor and Power Control

Process Control & Industrial Automation

Sensors and Sensor Interface

Temperature Controllers

Figure 4.Simplified Circuit Diagram of Fully Programmable Universal Analog Front End for Process Control Applications

Figure 5. EVAL-CN0209-SDPZ Evaluation Board Circuit Diagram (1)

Image 6. EVAL-CN0209-SDPZ Evaluation Board Circuit Diagram (2)
EVAL-CN0209-SDPZ Evaluation Board Bill of Materials (BOM):

Figure 7. EVAL-CN0209-SDPZ Evaluation Board PCB Layout
For details, see:
http://www.analog.com/static/imported-files/data_sheets/AD7193.pdf
and
http://www.analog.com/en/circuits-from-the-lab/CN0209/vc.html