User's Manual

Introduction www.ti.com
The Gas Sensor Platform with Bluetooth low-energy (BLE) is intended as a reference design that
customers can use to develop end-products for consumer and industrial applications to monitor gases like
carbon monoxide (CO), oxygen (O
2
), ammonia, fluorine, chlorine dioxide etc. . BLE adds a wireless
feature to the platform that enables seamless connectivity to an iPhone
®
or an iPad
®
. Customers can
easily replace the targeted gas sensor based on their application, while keeping the same analog front-
end (AFE) and BLE design. The system runs on a CR2032 coin-cell battery. AFE from TI — LMP91000 —
interfaces directly with the electrochemical cell. The LMP91000 interfaces with CC2541 which is a BLE
system on a chip from TI.
An iOS application running on an iPhone 4S
®
and newer generations or an iPad 3
®
and newer
generations lets customers interface with this reference platform. Customers can use and customize the
iOS application, the hardware files and firmware source code of CC2541, which TI provides as an open
source. The Gas Sensor Platform with BLE provides customers with a low-power, configurable AFE and
the option to integrate wireless features in gas-sensing applications. This platform helps customers access
the market faster and helps differentiate from performance, power, and feature sets.
The platform complies with the below certifications on wireless:
• EN 300 328 compliant
• FCC 15.247 compliant
• IC RSS-210 compliant
The platform complies with the below certifications on EMC:
• FCC – FEDERAL COMMUNICATIONS COMMISSION Part 15, Class B
• IC – INDUSTRY CANADA ICES-003 Class B
• EN 301 489-17
The heart of this reference platform is the AFE from TI, the LMP91000. The LMP91000 is perfect for use
in micropower, electrochemical-sensing applications. The LMP91000 provides a complete signal-path
solution between a sensor and a microcontroller that generates an output voltage proportional to the cell-
current. This device provides all of the functionality for detecting changes in gas concentration based on a
delta current at the working electrode.
The LMP91000 is programmed to support multiple electrochemical sensors, such as 3-lead toxic gas
sensors (see Figure 1-4) and 2-lead galvanic cell sensors (see Figure 1-5) with a single design as
opposed to multiple discrete solutions. The AFE supports gas sensitivities over a range of 0.5 to 9500
nA/ppm. It also allows for an easy conversion of current ranges from 5 to 750 µA, full scale.
The adjustable cell-bias and transimpedance amplifier (TIA) gain are programmed through the I
2
C™
interface. The I
2
C 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 micropower
applications, and operates over a voltage range of 2.7 to 5.25 V. The total current consumption can be
less than 10 μA. Additional power-saving capabilities are possible by switching off the TIA and shorting the
reference electrode to the working electrode with an internal switch
The LMP91000 supports many different toxic gases and sensors, and is configured to address the critical
parameters of each gas.
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Gas Sensor Platform Reference Design User's Guide SNOA922–April 2013
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