TI’s LMP91000 is a programmable low-power chemical sensor analog front end (AFE) that provides a complete signal path solution between the sensor and the MCU. Gas sensitivity from 0.5 nA/ppm to 9500 nA/ppm, easily converted to current from 5μA To 750μA. Working voltage 2.7V-5.25V, working current less than 10 μA, battery conditioning current up to 10mA, programmable battery bias voltage, low bias voltage drift. Mainly used in chemical sample identification, galvanometer and electrochemical blood glucose meter. This article presents the LMP91000 key features, block diagram, various application block diagrams, and chemical and gas sensor solution block diagrams and key features.
LMP91000 Sensor AFE System: Configurable AFE Potentiostat for Low-Power Chemical Sensing Applications
The LMP91000 is a programmable Analog Front End (AFE) for use in micro-power electrochemical sensing applications.
It provides a complete signal path solution between a sensor and a microcontroller that generates an output voltage proportional to the cell current. The LMP91000’s programmability enables it to support multiple electrochemical sensors such as 3-lead toxic gas sensors and 2-lead galvanic cell sensors with a single design as opposed to the multiple discrete solutions.
The LMP91000 supports gas sensitivities over a range of 0.5 nA/ppm to 9500 nA/ppm. It also allows for an easy conversion of current ranges from 5μA to 750μA full scale.
The LMP91000’s adjustable cell bias and transimpedance amplifier (TIA) gain are programmable through the the I2C interface.
The I2C interface can also be used for sensor diagnostics.
An integrated temperature sensor can be read by the user through the VOUT pin and used to provide additional signal correction in the μC or monitored to verify temperature conditions at the sensor.
The LMP91000 is optimized for micro-power applications and operates over a voltage range of 2.7V to 5.25V. The total current consumption can be less than 10μA. Further power savings are possible by switching off the TIA amplifier and shorting the reference electrode to the working electrode with an internal switch.
Main features of LMP91000:
Typical Values, TA = 25℃
■ Supply voltage 2.7 V to 5.25 V
■ Supply current (average over time) <10 μA
■ Cell conditioning current up to 10 mA
■ Reference electrode bias current (85℃) 900pA (max)
■ Output drive current 750μA
■ Complete potentiostat circuit to interface to most chemical cells
■ Programmable cell bias voltage
■ Low bias voltage drift
■ Programmable TIA gain 2.75kΩ to 350kΩ
■ Sink and source capability
■ I2C compatible digital interface
■ Ambient operating temperature -40℃ to 85℃
■ Package 14 pin LLP
■ Supported by Webench Sensor AFE Designer
LMP91000 application:
■ Chemical species identification
■ Amperometric application
■ Electrochemical blood glucose meter
Figure 1. LMP91000 block diagram
Figure 2. LMP91000 AFE Gas Detector Block Diagram
Figure 3. LMP91000 3-Wire Ammeter Unit Block Diagram
Figure 4. LMP91000 2-Wire Primary Cell Grounding Block Diagram
Figure 5. LMP91000 2-wire primary cell in a potentiostat configuration
Figure 6. LMP91000 Smart Gas Sensor Analog Front End (AFE) Connection Diagram on I2C Bus
Electrochemical sensors are widely used as a sense mechanism for gas and chemical sensing. Common applications include carbon monoxide detectors, chemical species identification, Amperometric sensors etc. Electrochemical sensors can be considered simply as transducers that convert the physical characteristic of gas/chemical concentration to an electrical signal which can be processed by instrumentation.
Signal Conditioning:
The programmable Analog Front End (AFE) is perfect for use in micro-power electrochemical sensing applications. It provides a complete signal path solution between a sensor and a microcontroller that generates an output voltage proportional to the cell current. The programmability enables it to support multiple electrochemical sensors such as 3-lead toxic gas sensors and 2-lead galvanic cell sensors with a single design as opposed to the multiple discrete solutions. The AFE supports gas sensitivities over a range of 0.5 nA/ppm to 9500 nA/ppm. It also allows for an easy conversion of current ranges from 5µA to 750µA full scale. The adjustable cell bias and Transimpedance amplifier (TIA) gain are programmable through the I2C interface. The I2C interface can also be used for sensor diagnostics. An integrated temperature sensor can be read by the user through the VOUT pin and used to provide additional signal correction in the µC or monitored to verify temperature conditions at the sensor. The AFE is optimized for micro-power applications and operates over a voltage range of 2.7V to 5.25V. The total current consumption can be less than 10μA. Further power savings are possible by switching off the TIA amplifier and shorting the reference electrode to the working electrode with an internal switch.
Signal Acquisition and Processing:
TI’s high resolution differential ADCs have low power consumption, wide dynamic range and low noise. This can be used to digitize the conditioned analog bridge output for high resolution, precision measurements. Alternately, one could use TI’s MSP430 microcontrollers with integrated ADCs and DACs. Further post processing algorithms can be run on this MCU.
Interface and Communication:
Traditional analog (4 – 20mA) interface remains the popular choice for industrial control and sensor applications. The other popular protocols include HART, Profibus and IO-Link. TI’s IO-Link interface products have integrated regulators and diagnostic outputs. In addition, wireless options based on IEEE 802.15.4 protocols are becoming more prevalent. TI is committed to provide solutions for both traditional and emerging industrial interfaces.
Power Management
The Field Transmitter can be powered in one of three ways. Line powered transmitters are commonly powered by voltage rails of 12V, or 24V. Loop powered transmitters are powered by the 4-20 mA loop. Such transmitters require extremely low power architectures as the entire solutions has to be powered off the loop. TI provides high efficiency Step Down converters with low quiescent current and low output ripple appropriate for Line and Loop powered transmitters. Battery powered transmitters powered can be designed using TI’s low power Buck and Buck-Boost converters. The DC/DC buck converters offer over 95% efficiency over a wide battery voltage range, even with input voltage down to 1.8 volts extending life. Special Buck-Boost battery converters generate a stable required output voltage and supply constant current for over- and under -input voltage conditions and support various battery configurations.
Figure 7. LMP91000 Chemical and Gas Sensor Solution Block Diagram
Solution main features:
Configurable AFE with integrated electrode excitation
One design solution fits multiple electro-chemical sensors
16-bit MCU for configuration and communication
Extremely low power extends battery life and ensures operation under 4mA
Enables online or factory programmed configuration and calibration of sensor
4-20mA Current Loop Transmitter
Integrated 5V regulator capable of providing system power
.05% span error
For details, see:
http://www.ti.com/lit/ds/symlink/lmp91000.pdf
TI’s LMP91000 is a programmable low-power chemical sensor analog front end (AFE) that provides a complete signal path solution between the sensor and the MCU. Gas sensitivity from 0.5 nA/ppm to 9500 nA/ppm, easily converted to current from 5μA To 750μA. Working voltage 2.7V-5.25V, working current less than 10 μA, battery conditioning current up to 10mA, programmable battery bias voltage, low bias voltage drift. Mainly used in chemical sample identification, galvanometer and electrochemical blood glucose meter. This article presents the LMP91000 key features, block diagram, various application block diagrams, and chemical and gas sensor solution block diagrams and key features.
LMP91000 Sensor AFE System: Configurable AFE Potentiostat for Low-Power Chemical Sensing Applications
The LMP91000 is a programmable Analog Front End (AFE) for use in micro-power electrochemical sensing applications.
It provides a complete signal path solution between a sensor and a microcontroller that generates an output voltage proportional to the cell current. The LMP91000’s programmability enables it to support multiple electrochemical sensors such as 3-lead toxic gas sensors and 2-lead galvanic cell sensors with a single design as opposed to the multiple discrete solutions.
The LMP91000 supports gas sensitivities over a range of 0.5 nA/ppm to 9500 nA/ppm. It also allows for an easy conversion of current ranges from 5μA to 750μA full scale.
The LMP91000’s adjustable cell bias and transimpedance amplifier (TIA) gain are programmable through the the I2C interface.
The I2C interface can also be used for sensor diagnostics.
An integrated temperature sensor can be read by the user through the VOUT pin and used to provide additional signal correction in the μC or monitored to verify temperature conditions at the sensor.
The LMP91000 is optimized for micro-power applications and operates over a voltage range of 2.7V to 5.25V. The total current consumption can be less than 10μA. Further power savings are possible by switching off the TIA amplifier and shorting the reference electrode to the working electrode with an internal switch.
Main features of LMP91000:
Typical Values, TA = 25℃
■ Supply voltage 2.7 V to 5.25 V
■ Supply current (average over time) <10 μA
■ Cell conditioning current up to 10 mA
■ Reference electrode bias current (85℃) 900pA (max)
■ Output drive current 750μA
■ Complete potentiostat circuit to interface to most chemical cells
■ Programmable cell bias voltage
■ Low bias voltage drift
■ Programmable TIA gain 2.75kΩ to 350kΩ
■ Sink and source capability
■ I2C compatible digital interface
■ Ambient operating temperature -40℃ to 85℃
■ Package 14 pin LLP
■ Supported by Webench Sensor AFE Designer
LMP91000 application:
■ Chemical species identification
■ Amperometric application
■ Electrochemical blood glucose meter
Figure 1. LMP91000 block diagram
Figure 2. LMP91000 AFE Gas Detector Block Diagram
Figure 3. LMP91000 3-Wire Ammeter Unit Block Diagram
Figure 4. LMP91000 2-Wire Primary Cell Grounding Block Diagram
Figure 5. LMP91000 2-wire primary cell in a potentiostat configuration
Figure 6. LMP91000 Smart Gas Sensor Analog Front End (AFE) Connection Diagram on I2C Bus
Electrochemical sensors are widely used as a sense mechanism for gas and chemical sensing. Common applications include carbon monoxide detectors, chemical species identification, Amperometric sensors etc. Electrochemical sensors can be considered simply as transducers that convert the physical characteristic of gas/chemical concentration to an electrical signal which can be processed by instrumentation.
Signal Conditioning:
The programmable Analog Front End (AFE) is perfect for use in micro-power electrochemical sensing applications. It provides a complete signal path solution between a sensor and a microcontroller that generates an output voltage proportional to the cell current. The programmability enables it to support multiple electrochemical sensors such as 3-lead toxic gas sensors and 2-lead galvanic cell sensors with a single design as opposed to the multiple discrete solutions. The AFE supports gas sensitivities over a range of 0.5 nA/ppm to 9500 nA/ppm. It also allows for an easy conversion of current ranges from 5µA to 750µA full scale. The adjustable cell bias and Transimpedance amplifier (TIA) gain are programmable through the I2C interface. The I2C interface can also be used for sensor diagnostics. An integrated temperature sensor can be read by the user through the VOUT pin and used to provide additional signal correction in the µC or monitored to verify temperature conditions at the sensor. The AFE is optimized for micro-power applications and operates over a voltage range of 2.7V to 5.25V. The total current consumption can be less than 10μA. Further power savings are possible by switching off the TIA amplifier and shorting the reference electrode to the working electrode with an internal switch.
Signal Acquisition and Processing:
TI’s high resolution differential ADCs have low power consumption, wide dynamic range and low noise. This can be used to digitize the conditioned analog bridge output for high resolution, precision measurements. Alternately, one could use TI’s MSP430 microcontrollers with integrated ADCs and DACs. Further post processing algorithms can be run on this MCU.
Interface and Communication:
Traditional analog (4 – 20mA) interface remains the popular choice for industrial control and sensor applications. The other popular protocols include HART, Profibus and IO-Link. TI’s IO-Link interface products have integrated regulators and diagnostic outputs. In addition, wireless options based on IEEE 802.15.4 protocols are becoming more prevalent. TI is committed to provide solutions for both traditional and emerging industrial interfaces.
Power Management
The Field Transmitter can be powered in one of three ways. Line powered transmitters are commonly powered by voltage rails of 12V, or 24V. Loop powered transmitters are powered by the 4-20 mA loop. Such transmitters require extremely low power architectures as the entire solutions has to be powered off the loop. TI provides high efficiency Step Down converters with low quiescent current and low output ripple appropriate for Line and Loop powered transmitters. Battery powered transmitters powered can be designed using TI’s low power Buck and Buck-Boost converters. The DC/DC buck converters offer over 95% efficiency over a wide battery voltage range, even with input voltage down to 1.8 volts extending life. Special Buck-Boost battery converters generate a stable required output voltage and supply constant current for over- and under -input voltage conditions and support various battery configurations.
Figure 7. LMP91000 Chemical and Gas Sensor Solution Block Diagram
Solution main features:
Configurable AFE with integrated electrode excitation
One design solution fits multiple electro-chemical sensors
16-bit MCU for configuration and communication
Extremely low power extends battery life and ensures operation under 4mA
Enables online or factory programmed configuration and calibration of sensor
4-20mA Current Loop Transmitter
Integrated 5V regulator capable of providing system power
.05% span error
For details, see:
http://www.ti.com/lit/ds/symlink/lmp91000.pdf
The Links: 2DI200A-050P MIG20J503L