FDC2212: FDC2212 steps in signal

Hi 

To debug this, please measure the oscillation amplitudes on both INxA and INxB of that specific channel. Ideally, both of those should be the same amplitude. Also, please share the amplitude of the devices which don't have this behavior. 

Regards

Sharath.

Hi Sarath, 

Because of coronna, i don't have access to an oscilloscope.

We add high loads to the measurement , therefore we run the measurement with a way to high IDRIVE. 

this allows us to measure over a wider impedance range with a minimized effekt of amplitude reduction.

9 of 10 measurementes deliver the expected results - a relativlely noisy but but stable measurement 

the idle amplitude is arround 3.5-3.6V (limited internally) 

is it possible, that the internall amplitude limiting circuit gets warm ands shows this effect? 

best regards Frido

Hi,

Thank you for providing the details of the test. 

Yes, you might correct about getting warm. Typically, we get the best performance with nominal operating conditions. There will be non-linearities and other effects with extreme conditions. You can run the test with lower IDRIVE settings to see if help with the noise? 

Regards

Sharath.

Hi Sharath, 

I've tested with optimum IDRIVE as well. (No amplitude warnings)

One of the units still shows the effect of steps in the signal. 

Can the chip be destroyed by a to high IDRIVE ?

best regards

Hi,

No, the chip won't be destroyed by high IDRIVE. It will have a lot of margin. 

Do you have a pico scope or other portable scope to measure the amplitudes of the channel? Is it possible to swap a good device on this noisy board to make sure that it is not related to board-related issues?

Let me know if you can d this testing.

Regards

Sharath.

Hi Sharath,

I swapped good and bad setups - the problem is related to the measurement.

Today, I measured the LC-tank amplitude of a bad measurement. 

With optimal IDRIVE  (looks good for me):

With to high IDRIVE: 

What do you think?

Regards

Hi,

The amplitude on the channels should be between 1.2V and 1.8V. Higher amplitudes on the sensor will have long term reliability issues. Please adjust the IDRIVE settings to meet the recommended voltage levels

Regards

Sharath.

please have a look at the graph with optimal drive current - the amplitude is 1.6V 

even then, i have steps in my signal...

What do you mean with "long term reliability issues"?

What else could cause steps in the signal when the amplitude is in range?

regards

Hi,

I am closing this as we are communicating through email.

Regards

Sharath.