Amplifier and Data Converter Selection Guide

44 Amplifiers
➔
Sensor Conditioners and 4-20mA Transmitters
The PGA309 is a complete voltage output
bridge sensor conditioner that eliminates
potentiometers and sensor trims. Span and
Offset are digitally calibrated with temperature
coefficients stored in a low-cost, SOT23-5,
external EEPROM. Excitation voltage
linearization, internal/external temperature
monitoring and selection of internal/external
voltage references including supply are
provided. Over/Under scale limits are settable
and fault detection circuitry is included.
The 4-20mA transmitter provides a versatile
instrumentation amplifier (IA) input with a
current-loop output, allowing analog
signals to be sent over long distances
without loss of accuracy. Many of these
devices also include scaling, offsetting,
sensor excitation and linearization circuitry.
The XTR108 provides a digitally controlled
analog signal path for RTD signal conditioning.
The XTR108 allows for digital calibration of
sensor and transmitter errors via a standard
digital serial interface, eliminating expensive
potentiometers or circuit value changes.
Calibration settings can be stored in an
inexpensive external EEPROM for easy
retrieval during routine operation.
RTD
XTR
4-20mA
4-20mA transmitter design solutions.
V LOOP
T
Fault
Monitor
V EXC
Digital Temperature
Compensation
Ext Temp
Auto-Zero
PGA
Linearization
Circuit
Analog Sensor Linearization
Int
Temp
Temp
ADC
Over/Under
Scale Limiter
PGA309 functional block diagram.
Ref
Linearization
DAC
Analog Signal Conditioning
Control Register
Interface Circuitry
4-20mA Transmitters and Receiver Selection Guide
V S
V S
Linear V OUT
DIGITAL CAL
EEPROM
(SOT23-5)
PGA309 Key Features
• Voltage output: ratiometric or absolute
• Digital calibration: no potentiometers, no
sensor trim
• Sensor compensation: span and span drift,
offset and offset drift
•