LDC1101EVM: LDC1101 EVM Max sampling freq

Johann Van Niekerk

Part Number: LDC1101EVM
Other Parts Discussed in Thread: LDC1101

Hey All.

Simple question.

The LDC1101 seems to have a maximum sampling frequency of 5.3uS, is this correct or am I reading it wrong ?

If correct or not, what settings ( sensors frequency, capacitor and inductance would give the best/ fastest response time.

From My testing the larger coils( inductance) has a very slow recover rate once triggered.

Thanx

7 months ago

0 Eddie LaCost 7 months ago

TI__Mastermind 39130 points

Hi Johann,

That is pretty close to the maximum sampling rate. For LHR measurements, setting the RCOUNT to the minimum value will provide the highest sample rate. For Rp+L mode, the sensor frequency will also have an effect on the sample rate, so a higher sensor frequency can help speed things up. You can use the LDC calculator tool in the LDC1101 tab below to adjust for different values as well.

https://www.ti.com/tool/LDC-DESIGN-TOOLS

0 Johann Van Niekerk 7 months ago in reply to Eddie LaCost

Prodigy 40 points

Hi Eddie

Thanx for the info, I have been playing with these numbers but have not been able to get any lower then 6uS. Is there another LDC ic with faster rate ?

With regards to the uS conversion rate. Would this rate be constant that could be offset as a constant.?

My target will be in range for around 15uS, but with 5uS sample rate that would mean sometimes I get 2 sample per event maybe 3. and these readings could take place anywhere within the 5us cycle if that makes sense. So does not seem like a constant offset would work.. Im trying to measure the time duration between two LDC1101 measurement points. So if the 5uS was constant on both sides then it wouldnt matter but thats not my understanding of it.

+1 Eddie LaCost 7 months ago in reply to Johann Van Niekerk

TI__Mastermind 39130 points

Johann,

For fast sample rates, LDC1101 is the recommended device. We have devices like the LDC131x and LDC161x, which offer higher resolution and more channels, but the sample rate is slower.

The LHR mode uses a constant conversion rate, but Rp+L mode varies based on sensor frequency. Keep in mind that with the lower RCOUNT values, you will lose effective resolution of the measurement(see table 1 for max sample rate). I would only suggest this for applications which have a large change that is being sensed as you must overcome the noise of a lower resolution measurement.

0 Johann Van Niekerk 7 months ago in reply to Eddie LaCost

Prodigy 40 points

Thanx for the info Eddie.

i tried the faster rate and the noise is an issue indeed. Im starting to wonder if a capacitive sensing approach is more suitable, FDC2x1y as an example