Process Control (Design Conference 2013)

Process Control Reference Designs and System Applications

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2

Today’s Agenda

Field Instruments Introduction 2-wire/4-wire systems—loop-powered vs. non loop-powered Communications

PLC/DCS Systems Introduction Analog input module Analog output module

Demo Update Circuits from the Lab® reference circuits

3

Industrial Field Instruments

4

Introduction

Industrial Control System

5

Sensing

Control Data/ Communication

Control

Process

Visualization

Field

Control Room

Field Instruments

Actuators PLC Control

High Level System Level Overview

Typical Sensor Actuator Network Architecture Control network options: industrial Ethernet, field buses, RS-485, CAN, … Field network options: 4 mA to 20 mA, HART®, IO-link, AS-interface, CC-

link/LT, CompoNet, RS-485, … Sensors and actuators available, which support field level and control level

connectivity

6


7

Field Instrument

Field Instrument—Sensors Temperature

Pressure

Flow

Level

Position

Angle

Acidity (pH)

Oxygen Content

Gas Detection

Corrosion

8

Two Categories of Transmitters

Loop-Powered 2-wire connection supplying both power and communication Power is supplied over the current loop from the control room Entire transmitter must operate on <3.2 mA for a standard transmitter and

<2.7 mA for a HART enabled transmitter

Non Loop-Powered 4-wire connection, two for power and two for communication No power consumption limitations Used in situations where sufficient power cannot be derived from the

current loop

9

2-Wire Connection, 4 mA to 20 mA Loop

Current Loop Carries Both: Information AND

Power for Instrument

Only Low Power Available Min voltage for instrument Usually specified as ≥12 V

Min current ≤4 mA

Total available power <50 mW

Low Power Design

10

ADC

Rsens ~250 Ω

4–20mA ANALOG INPUT

CONTROL SYSTEM

FIELD INSTRUMENT

24V DC.

POWER SUPPLY

2-WIRE CONNECTION

Field Instrument Signal Chain Loop-Powered Pressure Transmitter

11

Σ−∆ ADC

MU

X

DIFFERENTIAL PRESSURE (MAIN VALUE MEASURED)

STATIC PRESSURE (COMPENSATION)

TEMPERATURE (COMPENSATION)

Σ−∆ ADC

MCU FLASH SRAM

CALIBRATION

LINEARIZATION COMPENSATION

IN-AMP (PGA)

ADC (24-BIT)

IN-AMP (PGA)

ADC (24-BIT)

CLOCK

DAC (16-BIT)

4mA to 20mA DRIVER

DAC

COMMUNICATION POWER MANAGEMENT

VREF

LCD WATCHDOG

HART MODEM

4-20 mA +HART

VOLTAGE REGULATORS

(SPI)

(UART)

(I2C) DIAGNOSTICS

PROCESSING 32-BIT RISC

Loop-Powered System Architecture

Modem

ADC MCU

3.3V

FET

LOOP IN

LOOP OUT

10 V to 45 V supply 4 mA to 20 mA

DAC

LDO

R1 R2

Total Energy Available Under Worst Case 3.3 V at 4 mA

Circuit regulates current as appropriate via sense resistor

Current is modulated to deliver more or less current from FET as needed

I

The total system must run from <4 mA. This includes sensor/ADC/MCU/4 mA to 20 mA circuitry power. → Every parts needs to be as low power as possible..

12

Key Trends to Field Instruments

The Housing is Becoming Smaller Need for smaller parts Need for more integration Need for higher temp rated

parts Need for more efficient parts More safety targeted parts—

diagnostics

There Is a Trend for More Processing Requirements Lower power MCU cores Better processing capability

13

Pressure Transmitter (Loop-Powered Instrument)


14

Field Instrument Signal Chain Loop-Powered Pressure Transmitter

15

Σ−∆ ADC

MU

X




Σ−∆ ADC

MCU FLASH SRAM CALIBRATION LINEARIZATION COMPENSATION

IN-AMP (PGA)

ADC (24-BIT)

IN-AMP (PGA)

ADC (24-BIT)

CLOCK

DAC (16-BIT)

4 mA to 20 mA DRIVER

DAC


VREF

LCD WATCHDOG

HART MODEM

4-20 mA +HART

VOLTAGE REGULATORS

(SPI)

(UART)

(I2C) DIAGNOSTICS


Field Instruments—Analog Front End ADI SUCCESS: AD779x Family

16

Σ−∆ ADC

MU

X Differential Pressure (Main Value Measured)

Static Pressure (Compensation)

Temperature (Compensation)

Σ−∆ ADC

uC CALIBRATION LINEARIZATION COMPENZATION

In-AMP (PGA)

ADC (24-bit)

DIAGNOSTICS

In-AMP (PGA)

ADC (24-bit)

uC COMMUNICATION

HART MODEM

DAC (16-bit)

4-20mA Driver

DAC

LINEAR REGULATOR Intrinsic Safety

LINEAR REGULATORS

12V..50V 4-20mA

POWER MANAGEMENT

VREF

uC DISPLAY

LCD

SWITCH MODE REGULATOR >90% efficiency

WATCHDOGS

ADI’s Success: Low Power Sigma-Delta Cores Fully Integrated System on a Chip

Application—Thermocouple Sensor

Application Features

Cold-Junction Compensation Thermocouple voltage is proportional to

the temperature difference Second sensor needed to measure

temperature of the “cold junction”

Low Voltage Signal −20 mV to +80 mV FS 10 µV/°C to 50 µV/°C

Long Connections 50 Hz/60 Hz interference

Front-End Solution with 16- to 24-Bit Σ-Δ ADC AD7792/AD7793—low power, in-amp, voltage

reference, excitation currents, 50 Hz/60 Hz rejection AD7708/AD7718—up to 10 AIN channels, gain, 50 Hz/60 Hz rejection AD7719—2 × ADC, gain, excitation currents,50 Hz/60 Hz rejection

19

VOLTAGEREF.

ADC

FRONT - END

SER

IAL

INTE

RFA

CE

CALIBRATIONSDIAGNOSTICS

DIGITALFILTER

BIASVOLTAGE

AIN1

AIN2

IEXCMUX

CLOCK

REFINRREF

RT

METAL 1

METAL 2

THERMOCOUPLE

TERMINALBLOCK“COLD

JUNCTION”

Thermocouple V ~ (T1-T2)

Programmable Gain Amplifier

> 16-bit Resolution

Voltage Reference for Thermocouple Voltage

Serial Interface

50 /60Hz Rejection

Thermistor or RTD or Diode to measure T2

Excitation Current

AIN2 and REFIN to measure RT / RREF

Bias Voltage

Precision Analog Microcontroller


20

Field Instrument—Example Precision Microconverter

21

Σ−∆ ADC

MU

X




Σ−∆ ADC

MCU FLASH SRAM

CALIBRATION


In-AMP (PGA)

ADC (24-BIT)

IN-AMP (PGA)

ADC (24-BIT)

CLOCK

DAC (16-BIT)

4mA to 20mA Driver

DAC


VREF

LCD WATCHDOG

HART MODEM

4-20 mA +HART


VOLTAGE REGULATORS

(SPI)

(UART)

(I2C) DIAGNOSTICS

MU

X

ADuCM360

ADuCM360 Product Description

22

IDD: Cortex™-M3/SRAM/FLASH = 290 µA/MHz ADC – 70 µA per ADC PGA G = 4/8/16 = 130 µA PGA G = 32/64/128 = 180 µA DAC = 50 µA CPU = 500 kHz, both ADCs active, both PGAs =16, IDD = 1 mA (max)

Analog Performance: ADCs are 24-bit monotonic up to 500 SPS ADC ENOB > 21 RMS bits, fADC = 4 Hz ADC ENOB > 19 RMS bits, fADC = 50 Hz Simultaneous 50 Hz/60 Hz rejection at fADC=50 SPS, 80 dB Internal 1.2 V reference, Tempco = 4 ppm typ/15 ppm max DAC 12-bit monotonic

Other Details Specified for 1.8 V to 3.6 V operation (3.96 V compatible I/O) Packages: 7 mm × 7 mm, 48-LFCSP (complete system on a chip)

ADuCM36x Key Performance Specs—Low Power High Performance Analog Front End

23

Complete Closed-Loop Precision Analog Microcontroller Thermocouple Measurement System With 4 mA to 20 mA Output (CN0300) Description and Benefits: 4 mA to 20 mA loop is the standard

interface for communicating measured values from sensors to a controller

The ADuCM360, along with the ADP1720 LDO, provides a complete solution for loop-powered transmitter applications

Improve the overall system reliability and efficiency

Inputs: 4 mA to 20 mA loop Thermocouple RTD

End Market Target Applications

Key Parts Used

• Industrial • Field instruments • ADuCM360 Available now

24

4-20mA Interface


25

Field Instrument Example— 4 mA to20 mA Outputs

26

Σ−∆ ADC

MU

X




Σ−∆ ADC

MCU FLASH SRAM

CALIBRATION


IN-AMP (PGA)

ADC (24-BIT)

IN-AMP (PGA)

ADC (24-BIT)

CLOCK

DAC (16-BIT)

4mA to 20mA Driver

DAC


VREF

RS485 WATCHDOG

HART MODEM

4-20 mA +HART


VOLTAGE REGULATORS

(SPI)

(UART)

(I2C) DIAGNOSTICS

MU

X AD5421/22

AD5421—Integration, Accuracy, Performance, Safety

27

AD5421 Enhanced Diagnostic Features

AD5421 Fault Detect Features SPI interface watchdog timer SPI interface packet error check Loop current out of range Overtemperature Power supply monitor

29

HART Communication


30

Field Instrument Example— 4 mA to 20 mA Outputs

31

Σ−∆ ADC

MU

X




Σ−∆ ADC

MCU FLASH SRAM

CALIBRATION


IN-AMP (PGA)

ADC (24-BIT)

IN-AMP (PGA)

ADC (24-BIT)

CLOCK

DAC (16-BIT)

4mA to 20mA Driver

DAC


VREF

LCD WATCHDOG

HART MODEM

4-20 mA +HART


VOLTAGE REGULATORS

(SPI)

(UART)

(I2C) DIAGNOSTICS

MU

X

AD5700

What Is HART—Highway Addressable Remote Transducer

Global Communication

Standard

Enhances Measurement

Capability

Enables Diagnostics

Control System Field Instruments

HART DIGITAL DATA HART-ENABLED INSTRUMENTS

HART-ENABLED I/O MODULES

ANALOG 4 mA TO 20 mA

32

Why HART

Industry Trends: Need for more diagnostics Need for asset management Need for more communication

Traditional Analog 4 mA to 20 mA Interface… Single direction only Single channel—single value only Limited diagnostics—working/failing Limiting the system evolution

HART “Digital” communication option Analog 4 mA to 20 mA compatible Widely accepted, often implemented by

field instruments vendors Recently, wider adoption by PLC/DCS

vendors One of the trends in the process control

33

SENSOR

24 V DC

2-wire connection

4–20 mA DC

HART AC

AD5700 Integrated HART FSK Modem Simplifying Applications, Saving PCB Space Integrated Receive

Band-Pass Filter

Integrated Low Power 0.5% Precision Oscillator

High Output Drive Capability

34

Minimum External Components Required

AD5700: Lowest Power, Smallest Package Outperforming Existing HART Modems on Specifications That Matter

Industry-Leading Specifications Lowest power

consumption 178 µA demodulation

and reference Smallest package 24-lead, 4 mm × 4 mm

LFCSP Industry’s widest

temperature range –40°C to +125°C

Widest supply range VDD of 1.71 V to 5.5 V

38% Reduction in Power

75% Footprint Savings

60% Reduction in

External Components

35

Loop-Powered System Architecture—Example

Total Energy Available Under Worst Case 3.3 V at 3.5 mA

Modem

MCU

10 V to 45 V Supply 4 mA to 20 mA

DAC SENSOR

Total Current ~2.722 mA

Sensors Current

Resistive Pressure Sensor/RTD Temp Sensor ~0.8 mA

3.3v

ADC Cortex-M3 System on a Chip 2 x 24-Bit ADC Fully Running with Input Buffers 2 x Instrumentation Amplifier 2 (Gain = 16), Fully Running SPI, UART, Timers, Watchdog, Other Circuitry

Voltage Reference, RTD Current Source Reference

µC Core, FLASH, SRAM (Core Clock = 2 MHz) Clock Generator Total 1.72 mA

Hart Modem Current

0.157 mA

36

FET

R1 R2

3.3V LDO

LOOP IN

LOOP OUT

4 mA to 20 mA Output Stage Current

4 mA to 20 mA Output Circuitry, Including LDO ~0.225 mA

Field Instrument Demo

37

HART MODEM

50Ω

DAC

LOOP(–) CIN

HART_OUT

ADC_IN

3.3V

COM

3.3V

DEMO – AD5700D2Z

AD5421 ADuCM360 +

–

UA

RT

REGIN

SPI

COM

AD5700

ADC

V-REGULATOR

VLOOP

ADC 1

TemperatureSensor PT100

TEMP.SENSOR

REF

Vdd

Vdd

ADC 0 μC

SRAM FLASH Clock Reset

Watchdog

Iexc

COM

Watchdog Timer

3.3V Pressure Sensor Resistive Bridge

4-20 mA +HART

REGOUT

HART Physical Layer Specification Noise During Silence—System Design Challenging

39

Analog Rate of Change—Fastest Analog Signal Settling

Request for analog signaling step change e.g., 4 mA to 20 mA

HW filter combined with SW algorithm

Change split into

20 steps in 1 ms distance

Simple integer calculation in each step 1× multiplication 1× bit manipulation 1× integer addition Indexed table Write_DAC (DAC_previous + (DAC_diff ×

StepTable[i]) >> 16);

Analog signal settled in ~25 ms

40

LIMIT

LIMIT

DEMO-AD5700-D2Z—Complete ADI Solution for Industrial HART Communication

AD5700HART

Modem

SPIADC

UART

AIN(+)

AIN(–)

3.3V

DAC

LOOP(–)CIN

V-REG

HART OUT

HART IN

3.3V

COM

3.3V

AD5421ADuCM360

uC

CHART

CSLEW

+

–UART

REGIN

0-100%

SPI

REGOUT

Analog InputSimulation

CFILTER

41

HART Stack

ADI does not provide HART stack Plan to publish simplified example code for the demo ADuCM360 (configuration, PGA, 2× ADC, Vref, … ) AD5421 (SPI) AD5700 (UART) One HART command But not HART stack…

HCF does not provide HART stack on commercial basis

Some 3rd parties may provide this service

42

Communications


43

Field Instrument Example— 4 mA to 20 mA Outputs

44

4-20 mA +HART

Σ−∆ ADC

MU

X DIFFERENTIAL PRESSURE (MAIN VALUE MEASURED)



Σ−∆ ADC

MCU FLASH SRAM CALIBRATION LINEARIZATION COMPENZATION

IN-AMP (PGA)

ADC (24-BIT)

IN-AMP (PGA)

ADC (24-BIT)

CLOCK

DAC (16-BIT)

4mA to 20mA DRIVER

DAC


VREF

RS485 WATCHDOG

HART MODEM

PROCESSING 32-bit RISC

VOLTAGE REGULATORS

(SPI)

(UART)

(I2C) DIAGNOSTICS

MU

X

PROFIBUS CANBUS MODBUS

iCoupler® and isoPower® Isolation Products

®

45

Growth through Continuous Innovation and Industry Firsts

46

®

ADuM1100 First

iCoupler Digital Isolator

ADuM140x 4 Channels in

1 Package

ADM248x RS-485

ADuM120x 2 Channels in Narrow

SO-8

AD7400 Ʃ-Δ ADC

ADuM125x

I2C

ADuM1220 ½ Bridge

Gate Driver

ADuM240x 5 kV RMS Isolation

ADuM524x isoPower

ADuM5230 ½ Bridge

Driver with isoPower

ADM3251E

RS-232

ADuM7410 1 kV rms

ADuM4160 USB

ADM2582

RS-485 with isoPower

ADM305x

Cum

ulat

ive

Cha

nnel

s of

iCou

pler

Isol

atio

n [M

illio

ns]

ADE7913 Isolated

Metering AFE ADuM347x Switching Regulator

CANOpen Node

Customer Pain

Complexity of Solution

Size of Solution

Cost of Solution

Reliability of Solution (Optocoupler Wearout)

Robustness

47

ADM3053 Applications Diagram

48

PLC/DCS Systems

Programmable Logic Controllers

50

Industrial Control System

51

Sensing

Control Data/ Communication

Control

Process

Visualization

Field

Control Room

Field Instruments

Actuators PLC Control

Market Trends—Smaller/Faster Modules/Increased Channel Density Intelligent Integration

Smaller form factor

More channels in same area

Intelligent Power Mgmt

Smaller housing = heat

Integrated power control

52

Channel 4

Channel 3

Channel 2

Channel 1 Channel 1

Analog O/P Analog I/P

Channel 1

Channel 2

Channel 3

Channel 4

Analog I/P Analog O/P

Channel 1

Channel 2

Channel 3

Channel 4

Channel 2

Channel 3

Channel 4

Self-Heating Issue Lower Power Designs


53

Analog Outputs Integration Power Efficiency Performance

Trends to System Requirements…

Module Size Getting Smaller → Business Card Sizes Power dissipated per module reduced: was 5 W to 10 W, now 3 W to 5 W,

future 2 W to 3 W

Channel Density Increasing → 8/12/16 Channels Increases power dissipation

Increased Speed (Settling) for Factory Automation Down to 20 µS for analog output channels → still require efficiency

Increased Safety Requirements for Process (SIL) Increased diagnostics/robustness

50

Innovation Evolution for Industrial Outputs

55

First Quad Universal Output Solution First Integrated Dynamic Power Control Integrated Functions and Diagnostics Fully Programmable Outputs

OP2177

OP2177

OP2177

OP2177 AD5664

Discrete Solution Quad DAC + Ext Gain Amps

Vout Iout

AD5750

Vout Iout

AD5750

Vout Iout

AD5750

Vout Iout

AD5750 AD5664

Semi-Integrated Solution Quad DAC + 4 Ext Drivers

Vout Iout

AD5422

Vout Iout

AD5422

Vout Iout

AD5422

Vout Iout

AD5422

Fully Integrated Single-Channel Solution

Vout Iout

Vout Iout

Vout Iout

Vout Iout

AD5755

Fully Integrated Quad Channel Solution NEW

Significant reduction in board area Minimal External Components Required Manages and Reduces Power and Heat

Efficiently Decreases TTM and Cost of Ownership

Universal Output Module with Embedded Dynamic Power Control Technology 4 Channels Enabled Driving 20 mA into Zero Ohm Load: Case 1: without dc-to-dc control enabled (pink) Case 2: with dc-to-dc control enabled (blue)

On-Chip Die Temperature Low When DC-to-DC Regulation Enabled

56

AD5755 Change in Temperature calculations

-50

0

50

100

150

200

250

0 5 10 15 20 25 30

Time (s)de

lat T

(°C

)

DC/DC 0 Ohm VBOOST 30V 200Ohms

In Production

System Outputs—Most Common Architecture

Main Micro

BUS

System Power -24 V Nom

DAC

Sign

al

Isol

atio

n

DC-DC Isolated Power Stage

28V

3.3V

ADP2441

-28V

5V

ADUM2485

Watchdog

Supervisor

DAC

DAC

DAC

.

.

.

.

20ma @ 1K

Analog Outputs: Driving 20 ma into 1 K load needs 20 V compliance. Adding headroom supply for DAC; Supply ~ 24 V. Including output regulation of the power stage a good estimate is 28 V. A short is a valid condition. This is mainly because ADC modules can be terminated with resistor values as low as 20 Ω for sensing. Therefore, an 8-channel module can dissipate up to 4 W from the analog portion alone. Include power losses from the dc-to-dc stage (say 80%) power loss can reach >6 W for the analog portion alone.

58

Precision 16-Bit DAC

AD5755 Block Diagram Dynamic Power Control

Diagnostics

I

30V

0-24mA

0 Ω load

I

5V

24mA

0Ω load

DC-DC

Voltage and Power is Dynamically Adjusted

Smart and High Efficiency Dynamic Power Control

(DPC)

59

Dynamic Power Control

DAC

Main Micro

BUS

System Power -24 V Nom

L

Sign

al

Isol

atio

n

DC-DC Isolated Power Stage

15V

3.3V

ADP2441

-15V

5V

ADUM2485

Watchdog

Supervisor

20mA at 0Ω DC-DC

C L

DAC

L 20mA at 0Ω

DC-DC

C L

AD5755 QUAD DAC

The addition of a per dc-to-dc to implement dynamic power control allows for individual power losses per channel to be minimized. Under a short condition for eight channels, the dc-to-dc regulates the output to 7.5 V, thereby limiting both on-chip power dissipation and module power dissipation. Assuming a dc-to-dc isolated stage of 80%, the total power dissipated using the dynamic power control for the 8-channel module is 3 W.

60

AD5755/AD5757 Output Ripple

Waveform of output ripple Yellow = IOUT Blue = VBOOST

(at 20 mA dc, 1 kΩ load)

Per Channel DC-to-DC Circuitry Circuitry at IOUT

Example of settling “shape”

(0 mA to 20 mA, 1 kΩ load)

With 0 nF capacitor at IOUT

7.6 mVp-p output ripple at 20 mA dc

≈ 580 µs settling time


4.24 mV p-p output ripple at 20 mA dc



1.68 mVp-p output ripple at 20 mA dc


61


62

Analog Inputs Trends in Analog Inputs Better Robustness: Overvoltage Protection Better Rejection of 50 Hz/60 Hz

High Speed/Performance ADC Cores

PLC/DCS Analog Inputs—Input Signals

10 V 0 V to 10 V ±10 V

20 mA Industrial standard 4 mA to 20 mA loop 0 mA to 20 mA loop

RTD Resistive temperature device Pt100, Ni1000, Cu10, …

Thermocouple Two metals connected together Low voltage (mV) ~ (T1-T2) Second temperature sensor (CJC)

10 V DC

0 – 10V

AIN

SENSOR 24 V DC AIN

ADC

AIN

A

ADC

ADC

DIVIDER

EXCITATION ~mA

AIN A ADC

T1 T2

Metal A

Metal B

Copper

Copper

Sens. (CJC)

Rsens

63

ADA4096-x – 36V OPX96 Performance 36V, RRIO, Precision, µPower, RRIO Op Amp with OVP Key Features Internal input overvoltage protection (OVP) Up to ±32 V beyond the rails Characterized OVP parametric impact

(compared to external OVP solutions) Low power: 60 µA typical Unity GBW:800 kHz at Vsy = ±15V typical

550 kHz at Vsy = ±5 V typical 475 kHz at Vsy = ±1.5 V typical

Low offset voltage: 35 µV typical

Applications Process control (PLC/DSC) Battery monitoring and current shunt sensing Sensor conditioning Portable instrumentation Wireless base stations

64

Isy GBW Vos Vos Drift Noise IB Voltage Temp Range

75 µA max 800 kHz typ 300 µV max 1 µV/°C typ 27 nV/√Hz typ 25 nA max 3 V to 30 V ˗40°C to 125°C

ADA4096-2 Dual Released ADA4096-4 Quad Production

Package: MSOP-8, LFCSP-8 (3 × 3) List Price: $1.87 at 1k units

Package: TSSOP-14, LFCSP-14 (3 × 3) List Price: $2.70 at 1k units

ADI Advantages With 2× the BW, ½ Vos and 1/3 TcVos, ½ Vn of

the closest competition, and 32 V Input OVP; the ADA4096 provides the industry’s highest level of

overvoltage protection for robust operation in demanding I&I applications

External Diode Protection Advantage Cheap solution

Disadvantage Not suitable for some

applications (i.e. precision)

Variable leakage current Variable capacitance Increase in nonlinearity Need external circuitry

Differential Diode Protection Advantage Cheap solution Constant leakage

current and capacitance

Disadvantage Need external circuitry Does not work when powered off Large Rlimit resistance will add noise to the

system

ADI OVP Solution Advantage Integrated OVP solution Provides most, if not all

protection needed Saves board area Prevents phase inversion beyond IVR

Disadvantage Might need extra external protection for

OVP beyond the protection limits

Surveying Various Internal and External OVP Solutions Internal ESD Protection

Advantage Cheap solution

Disadvantage Not robust enough

65

ADA4096

ADI’s OVP Op Amps

Overvoltage protection op amps: The most robust solution available Effects are included in data sheet specifications No phase inversion to the protection limits

(beyond the IVR) No external circuitry required Protects indefinitely and with power on or off

It is able to protect op amps and entire circuitry from: Input voltages above supply rails Manufacturing shorts Human error Transducers which produce voltages higher than supply rails

OVP is able to protect circuits from various unexpected errors, which in turns saves $$

66

ADA4091 ADA4096

Analog to Digital Converter


67

AD7176 Flexible Filter Options

Sinc3

Sinc5+ Sinc1

Enhanced Filters

AD7176 Maximize 50 Hz/60 Hz rejection Reduced settling time Improved channel switch rates 50 Hz and 60 Hz combined

Standard SD ADC filter Best noise performance and resolution Best choice for single channel high resolution Performs best at lower speeds

New filter design Fast channel switching with quickest settling Best performance at higher speeds

68

Improved Interface Robustness

CS rising edge resets the serial interface into a known state No reset required if interface synchronization is lost

Writing to AD7176 Reading from AD7176

CRC checksum prevents data corruption on digital interface Work on both reads and writes

Internal register checksum Validation of ADC configuration

69

Enhanced Filtering Simultaneous Rejection of 50 Hz and 60 Hz Multichannel 50 Hz/60 Hz Rejection

Fastest 50 Hz/60 Hz Rejection on the Market

Output Data Rate (SPS)

tSETTLE

(ms) Ch. Switch Rate =1/tSETTLE (Hz)

Rej. Of 50 Hz and 60 Hz (±1 Hz) (dB)

AD7176 Noise-Free Bits

27.27 36.67 27.27 47 23.3 25 40.0 25 62 23.3 20 50.0 20 85 23.5 16.667 60.0 16.667 90 23.5

Trading Faster Channel Switch Rates vs. Rejection

70

Motor Control/Data Acquisition: Faster Speed/ Robotics, Set Point Control

71

ADC

Rsens ~250 Ω

4mA to 20mA ANALOG INPUT

FIELD INSTRUMENT (SENSOR)

2-WIRE CONNECTION

DAC

ANALOG OUTPUT

4mA to 20mA FIELD INSTRUMENT (ACTUATOR)

2-WIRE CONNECTION

1K

IO MODULE

FASTER SETTLING PRODUCTIVITY EFFICIENCY CONTROL

Sinc5 + Sinc1 Filter Maximizing Channel Switch Rate Multichannel applications Max channel switch rate = 50 kSPS/channel Single cycle settling at < 10 kSPS ODR

Output Data Rate (ODR) (SPS) tSETTLE

Switching Rate (SPS)

F Notch (Hz) Noise (µV RMS)

Resolution (p-p) Noise-Free bits

(5 V Vref) 250,000 20 µs 50,000 250,000 9.7 17.25 50,000 36 µs 27,778 50,000 5 18.2 25,000 56 µs 17,857 25,000 3.6 18.7 15,625 80 µs 12,500 15,625 2.7 19.1 10,000 100 µs 10,000 11,905 2.5 19.2 1,000 1.0 ms 1,000 1,016 0.82 20.8 100 10.0 ms 100.0 100.16 0.46 21.7

59.94 16.68 ms 59.94 60.00 0.43 21.7 49.96 20.016 ms 49.96 50.00 0.42 21.8

16.667 60.02 ms 16.66 16.67 0.42 21.8 5 200.02 ms 5.00 5.00 0.32 22.1

66

AD7176-2, 24-Bit, 250 kSPS, 20 µs Settling Σ-Δ ADC

Fast and Flexible Output Data Rates 5 SPS to 250 kSPS 17.2 noise-free bits at 250 kSPS Flexible filter options Fastest 50 Hz/60 Hz rejection Fast settling—50 kSPS/channel scan rate INL 2.5 ppm typical Integrated 2.5 V reference (2 ppm) and

oscillator Per channel configuration and calibration Cross point mux with automatic sequencing

AIN 0

AIN 1

AIN 2

AIN 3

AIN 4AVSS

CrosspointMultiplexer

AVDD

Σ-Δ ADC

AVSS

SERIALINTERFACE& CONTROL

CS

SCLK

DIN

DOUT/RDY

SYNC/ERRORI/O

CONTROL

GPIO 0 GPIO 1

AVDD1 AVDD2

1.8VLDO

REGCAP A IOVDD

1.8VLDO

REGCAP D

DGND

BufferedPrecisionReference

REF+REF- REFOUT

XTAL1 CLKIO/XTAL2

XTAL & INTERNALCLOCK OSCILLATOR

CIRCUITRYAD7176-2

INTREF

DIGITALFILTER

Noise-Free P-P Bits

Channel Switch Rate

17.2 50 kSPS

18.5 31 kSPS

20.2 2.5 kSPS

23.5 20 SPS

73

Process Control Demo

Demo Station

74

Demonstration Overview

75

Loop-Powered, 4 mA to 20 mA + HART Interface with AD5421 + AD5700 (CN0267) Description and Benefits: 4 mA to 20 mA loop is the standard

interface for communicating measured values from sensors to a controller

HART (Highway Addressable Remote Transducer) protocol is the global standard for sending and receiving digital information across analog wires

The HART communication enables better diagnostic capabilities and asset management

Improve the overall system reliability and efficiency

Inputs: 4 mA to 20 mA loop Standard resistive pressure sensor

End Market

Target Applications

Key Parts Used

• Industrial

• Field instruments

• Smart transmitter

• AD5700 • AD5421 • ADUCM360

Available now

76

This demo board is available for purchase: www.analog.com/DC13-hardware

http://www.analog.com/DC13-hardware

DEMO-AD5700-D2Z—Complete ADI Solution for Industrial HART Communication (Transmitter Side)

AD5700HART

Modem

SPIADC

UART

AIN(+)

AIN(–)

3.3V

50Ω

DAC

LOOP(–)CIN

V-REG

HART OUT

HART IN

3.3V

COM

3.3V

AD5421ADuC

uC

CHART

CSLEW

+

–UART

REGIN

0-100%

SPI

REGOUT

Analog InputSimulation

CFILTER

77

Isolated, Single Channel Universal Analog Input (Voltage, Current, Thermocouple, RTD) with Overvoltage Protection (CN0325) Description and Benefits: Single channel analog front end

for process control systems Overvoltage protection Universal analog input Channel-to-Channel isolation

Inputs: Voltage Current Temperature (thermocouple + RTD)

End Market Target

Applications Key Parts Used

• Industrial • PLC/DCS • AD7795 • ADuM3471 • ADT7310

Available now

78



Isolated (ADUM347x), Single Channel, Voltage and Current Output (AD5422) with HART (AD5700) Suitable for Channel-to-Channel Isolated Systems (CN0321) Description and Benefits: Single channel analog output for

process control systems HART enabled Current and voltage output ranges Channel-to-Channel isolation

Inputs: Digital inputs

End Market Target Applications

Key Parts Used

• Industrial • PLC/DCS • ADUM3471 • AD5422 • AD5700

Available now

79



Tweet it out! @ADI_News #ADIDC13

What We Covered

Introduction to Industrial Control

Understand Field Instruments and PLC/DCS

Market Trends and ADI Products to Support This

Demo of ADI Process Control Boards

80

Reference Circuits

Some Other Relevant Circuit Notes for Process Control: Transmitters Complete closed-loop precision analog microcontroller thermocouple

measurement system with 4 mA to 20 mA output (CN0300) 4 mA to 20 mA loop-powered temperature monitor using the

ADuC7060/ADuC7061 precision analog microcontroller (CN0145) Complete thermocouple measurement system using the AD7793 24-bit

Sigma-Delta ADC (CN0206) EMC Compliant RS-485 transceiver protection circuits (CN0313)

PLC/DCS Precision 24-bit, 250 kSPS single-supply Sigma-Delta ADC system for

industrial signal levels, using the AD7176 (CN0310) Software configurable, universal analog front end for industrial and sensor

data acquisition (CN0209) High accuracy multichannel thermocouple measurement solution (CN0172) 4 channels, flexible, configurable, voltage and current output circuit for I/O

card and PLC applications (CN0229)

81

http://www.analog.com/CN0300








Date post:	17-Jun-2015
Category:	Technology
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