AFE Eval Platforms Merit Closer Look

I met with an engineering team at Texas Instruments while I was attending DesignCon in Santa Clara, Calif. The engineers showed me a new analog front end (AFE) IC they have released. More semiconductor manufacturers are starting to turn out AFE ICs. This one is intended for use with three-terminal electrochemical gas sensors.

The AFE device looks pretty straightforward.

The TI LMP91000 AFE.

The TI LMP91000 AFE.

What makes this one unique is the Eval platform the apps guys there put together. Except for the gas sensor cell and the 3V lithium coin cell to power it, all the important parts are from TI. There's the LMP91000 device (shown above), a TPS61220 boost converter, an LM4120 LDO, and the CC2541 Bluetooth IC. The Eval module also has two circuit boards and the usual small number of connectors or headers, resistors, and capacitors.

The complete coin cell-powered, Bluetooth-linked AFE module.

The complete coin cell-powered, Bluetooth-linked AFE module.

The boost converter is needed just to give the AFE and chemical cell sufficient voltage over the life of the battery. It's a very high-efficiency device, which it must be for a battery-operated device. Also, the LDO is the right part for battery apps. The input-to-output differential is very low, and so is the quiescent current.

What makes this device even more special is the time it took the apps team to put this together. From the initial concept through schematic capture, PCB layout, writing the software, and assembling the first prototype, the total elapsed time was 11 days. The implications for anyone working on a similar design (the companies in western Pennsylvania come immediately to mind) are obvious.

The unit I saw had an O2 sensor, but the same AFE can work with sensors for H2 S, CO, and CO2 . The total current draw is around 40uA, so it can run more than six months on the coin cell. TI demonstrated the sensor with an iPad app to show O2 concentration in the air. Fortunately, it was around 20 percent, so everyone in the room could breathe easy.

Gas sensors like this will see use at oil refineries and by firefighters and mine workers. Portable blood analyzers can also benefit from the technology. For all these applications, the threat of toxic or life-threatening gases is extremely serious, so the work TI's engineers are doing is especially good humanitarian work.

7 comments on “AFE Eval Platforms Merit Closer Look

  1. eafpres
    February 3, 2013

    Hi Brad–this is totally cool.  The TI guys have been leading the ultra-low power wireless area, and adding integration to integrate to senosrs will just make it that much easier for users.  This enables connecting all sensors in your building or factory to Bluetooth (Low Energy, of course) then using gateways to aggregate all those BT devices onto a LAN or WLAN (WiFi).  Bingo, you have your analog sensors on your network.

  2. Brad Albing
    February 4, 2013

    I agree – cool stuff. I hadn't been watching TI's low power devices much, but now that I see what they're doing, I'll pay more attention. Their devices should be useful for companies doing smart home, home automation, and remote [utility] meter reading apps.

  3. jkvasan
    February 5, 2013

    AFEs from TI are very valuable. I have been using the ADS1298R for ECG application. It provides easy integration with MCU and has everything a good ECG preamp has. What interested me most was, the device was able to do all this with separate 24 bit ADCs for each channel. Simultaneous sampling of signals – to the letter.

  4. Brad Albing
    February 12, 2013

    Hmm… multiple ADCs? Very nice. I've been involved in some product designs in the past that could have greatly benefitted from such an IC.

  5. Joshua Israelsohn
    February 15, 2013

    Tres cool application development tool!

    This reminds me of a challenge for designers of transducer based systems: Performance confirmation for transducers and their signal conditioners requires a reference in the transducer's input domain . In this case, for example, one would need reference gas samples to confirm a gas detector's baseline and span accuracy.

    I know there are a number of ways of confirming gas composition, but there are other transducer types with less obvious references. An example that I've found vexing is that of acoustic measurements: Acoustic transducers  speakers  are characterized with measurement microphones. Does anyone know what manufacturers use to calibrate or confirm the response of the measurement microphones? Where do you buy reference SPLs over a spectrum?


  6. Brad Albing
    March 28, 2013

    Oh – and medical apps – sorry – forgot that one – both in the hospital/clinic and in the home. That's what I was hinting at w/ “western PA.”

  7. Brad Albing
    March 28, 2013

    Just to be clear – you'll still want a good intrmentation ampto be able to achieve the needed very high CMRR.

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