Finding a low power IC for programmable(i2c) window frequency comparator (supervisor & reset)

Hi,

Base on your application, you can try the TPS3899 or TPS37x.  Both of these parts have a voltage threshold and frequency detection.  Both of these parts do not need I2C.  Have you check to see if any other GPIO based solutions can work for your application?  

The TPS37X can be programmed to sense a voltage at a set time.  When the voltage is above or below the threshold setting, a timer begins counting and if the sensed voltage is not detected at the programmed time, a fault signal is generated.  Also, if the frequency is varying where the voltage amplitude does not reach the programmed voltage threshold at the programmed time, a fault signal is generated.  There is an application in the TPS37X that describes something similar to what you are trying to achieve with your application.

The TPS3899 is a low voltage part with similar features of the TPS37X.

Good luck!

Ben 

Hi Ben,

Thanks for your reply, nano-power is exactly what I need, but seems the TPS3899 or TPS37x do not completely match my application because:

1. My input signal is an analog sine wave or a pulse after convert, and the frequency of the input signal may change according to a different environment(wind speed change), I hope I can monitor the frequency-changing and read the value out.

2. I need the run time software programmable, beside I2c, GPIO is also fine, to set the new threshold.

Kind regards,

Hansen

Hi Hansen,

1. My input signal is an analog sine wave or a pulse after convert, and the frequency of the input signal may change according to a different environment(wind speed change), I hope I can monitor the frequency-changing and read the value out.

You can try to rectify your analog sine wave, like what you see in the TPS37x on pg. 20.  Below is the picture that I am referring to:

2. I need the run time software programmable, beside I2c, GPIO is also fine, to set the new threshold.

Are your voltage thresholds changing over time or can they be a fixed threshold?

Ben 

Hi Ben,

Thanks, the thresholds are changing over time, I recorded a video as shown in the following when the wind speed changing, the wave how it looks like:

The highest frequency is less than 1kHz at wind speed about 37 m/s, this is the highest the product will support.

Hi Hansen,

Thanks for the video.  I have a better understanding of your application.  I really believe the TPS37x voltage supervisor can be a solution for your application.  What if you rectified the pulse waveform signal into a DC voltage?  If the windspeed slows down, your DC voltage will go down.  You can set a threshold voltage where the slowest windspeed will yield the lowest DC voltage and if the rectified voltage goes below the set threshold voltage, the voltage supervisor will output a "fault" signal?

Ben

Hi Ben

My name is Bluto, I'm hardware, Hansen's colleague.

Ablout our application, please allow me to add some information.

• We want to measure the wind speed, from 1m/s to 30+ m/s, we hope to be able to catch the change of every 1m/s or 0.5m/s, so there should be 30 or 60 threshold voltage level which can switch. (TPS37x seems only can set by  external components.)

• Our current plan
  1. sampling, get a sine wave that varies with frequency.
  2. reshaping, change the sine wave into fixed width pulse signal via Monostable Multivibrator (SN74LVC1G123)
  3. rectifying, pulse to DC voltage.
  4. DC voltage input ADS1114, if wind speed change, ADS1114 alarm, cpu wake up to reading data. If wind speed remain constant, cpu always on standby. It all about getting a very low power consumption.

Q1:  About step 3, rectified the pulse waveform signal into a DC voltage, Is there a better way? 

Q2:  Do you think TPS37X still meets our requirement?

Q3:  Whether ADS1114 is a good choice?

Kind regards,

Bluto

Hi Bluto,

See my response in red below:

Q1:  About step 3, rectified the pulse waveform signal into a DC voltage, Is there a better way? 

That is a good question.  I believe you would need to convert the signal to a DC voltage so its information can be usable for the TPS37x.

Q2:  Do you think TPS37X still meets our requirement?

Can I ask why you need to sense every 0.5 m/s to 1 m/s of change in wind speed?  That part I need more information from you.  From what Hansen said in his first post, he is looking for a low power supervisor that can detect a fault when the frequency is outside the programmed threshold range.  The TPS37x can do that where it can be used to detect a too fast or too slow frequency range.

Q3:  Whether ADS1114 is a good choice?

Again, I am not sure about the application but I believe the ADS1114 may be a solution as well for your application.  I still think the TPS37x will be a good and simple solution to your application.

Ben 

Hi Ben，

About our application:

1. We need to measure the wind speed, this is our core function.
2. This is a battery-powered device, so ultra-low power consumption is necessary.
   1. When there is no wind, the system stands by.
   2. When wind blow, system wake up and measure.
   3. There is also a situation, The wind keep blowing. This will consume a lot of power.
   4. So we hope system only wakes up when the wind speed changes. That's the reason we need to sense every 0.5m/s or 1m/s change in wind speed.

So I think TPS37X only apply to "a, b", right ? 

ADS1114 seems can be set the alarm voltage threshold via i2c interface.

Do you have any other Suggestions, please?

Best regards

Bluto

Hi Ben,

Sorry for our late reply, as your suggestions, we are planning to use TPS37x as an option in the product, we need to do some further integration for the next evaluation.

Thanks for your help!

Hi Hansen,

Glad to be of help!  Please keep me updated!  Good luck!

Ben