LDC2114EVM: About the calculation method of the value of OUT of LDC2114

Hello,

Unfortunately I'm not able to share exactly how OUT is calculated. For applications that can use the LDC2114, the exact equations are not necessary. However, this application note discusses the internal algorithms that are applied to the raw data. There is pseudo code for some of them, which may give you a better idea of how the raw code is being modified.

Best Regards,

Hello, Mr. Kristin.

Thank you for your quick reply.

■ About the matter of not knowing the calculation of OUT DATA(Resister 0x02-0x09)

Even if you know how much the frequency has changed with respect to the frequency at the initial position, you can not determine the threshold without knowing what it will be as the value of OUTDATA
The frequency-target distance characteristics can be simulated (when the target conductor is made of aluminum by using Spiral Inductor designer). This characteristic shows the amount of frequency change with respect to the distance change of the target
The relationship between the amount of deflection of the button and the amount of frequency change can be understood
From the button shape and the target thickness, the relationship between the pressing force and the deflection amount is obtained.
From the above, the relationship between the amount of frequency change and the amount of change of OUT DATA becomes important. If you do not know this, you can not set the exact threshold (128 + Hysteresis, 128-Hysteresis).

What do you think?

Since the output value (12 bits) is calculated from register 0x02-0x09 (DATAx) based on the LC sensor frequency, it cannot be understood that the calculation formula cannot be understood. Is there anyone who knows this?

Part of the sensor design procedure I consider

1 coil design
->Characteristic of frequency-target distance is obtained (with Spiral Inductor designer)
2 Determine the distance between coil and target
->Initial LC frequency determined
3 Determine the rough threshold (128 + α)  Hysteresis ?
4 Determine the amount of change in frequency (DATA) due to button push from the threshold value
5 Find the relationship between the amount of change in DATA and the amount of actual change in LC frequency  (* important)
6 Determine the deflection of the target from the required frequency change
7 Determine the thickness of the button from the amount of deflection, the shape of the button, and the pressing force
※ Target conductor is aluminum

I think that will be the procedure. Is it wrong?

Anyway, I would like to know the relationship between data and sensor frequency.
I understand that frequency is expressed as a relative value.

Best regards/

Hello! Kristin

I’m sorry for the late reply.

Thank you for your information.

I have already read all documents related to LDC2114.

Snoa961, Snoa963, snoa993, data sheet, snou144, snaa302, snaa307

Still not sure. There is an impression that the design method is the same as the actual method to match the mechanism (including the sensor).

By Snoa963

1. Design the coil (Spiral Inductor Sesigner)

2. Design the mechanical part of the button part (determine the conductor thickness and holding method of the button part)

3. Read the current GAIN value (GAINnFACTORold)

4). Apply a predetermined pressing force (for example, 100 g) to the button part incorporating the sensor

5. Read output DATA Code (DATAn)

6). Calculate the new gain setting value (GAINnFACTORnew) from the formula and use it as the new setting value.

GAINnFACTORnew=SWICTHING_THRESHOLD x GAINnFACTORold) / DATAn

I don't know how to use LDC2114.

Please tell me about the correct design procedure.

What I am looking for

・Press force on the button part 3.54N

・I want to get DATAn twice the threshold ON value with this pressing force.

・Coil design size Φ13 mm (in the experiment, LDCCOILEVM M coil is used)

・The button size is φ20mm or 12x20mm.

・I want to find the thickness of the button at this time. Actually it is ABS resin, and aluminum tape (100μm) is pasted as a conductor.

(At the point of skin depth, depending on the frequency, more than 100μm may be required)

“Metal Deflection” is used to determine the thickness of the button, but here, not only the size but also the amount of deflection is required. The amount of deflection is the source of changes in DATA. This is why I say that the relationship between the amount of deflection and the amount of change in DATA is necessary. Please tell me the correct design procedure. 

.

Best regards

Hello! Kristin

I’m sorry for the late reply.

Thank you for your information.

I have already read all documents related to LDC2114.

Snoa961, Snoa963, snoa993, data sheet, snou144, snaa302, snaa307

Still not sure. There is an impression that the design method is the same as the actual method to match the mechanism (including the sensor).

By Snoa963

1. Design the coil (Spiral Inductor Sesigner)

2. Design the mechanical part of the button part (determine the conductor thickness and holding method of the button part)

3. Read the current GAIN value (GAINnFACTORold)

4). Apply a predetermined pressing force (for example, 100 g) to the button part incorporating the sensor

5. Read output DATA Code (DATAn)

6). Calculate the new gain setting value (GAINnFACTORnew) from the formula and use it as the new setting value.

GAINnFACTORnew=SWICTHING_THRESHOLD x GAINnFACTORold) / DATAn

I don't know how to use LDC2114 yet．

Please tell me about the correct design procedure.

What I am seeking is “Relationship between deflection amount and DATAn”.

Design requirements

・Press force on the button part 3.54N

・I want to get DATAn twice the threshold ON value with this pressing force.

・Coil design size Φ13 mm (in the experiment, LDCCOILEVM M coil is used)

・The button size is φ20mm or 12x20mm.

・I want to find the thickness of the button at this time. Actually it is ABS resin, and aluminum tape (Thickness100μm) is pasted as a conductor.

(At the point of skin depth, depending on the frequency, more than 100μm may be required)

“Metal Deflection” is used to determine the thickness of the button, but here, not only the size but also the amount of deflection is required. The amount of deflection is the source of changes in DATA. This is why I say that the relationship between the amount of deflection and the amount of change in DATA is necessary. Please tell me the correct design procedure.

Best regards

H.Sano

PS:I was very sorry to send you with Mr.the other day.

Hello,

Unfortunately the algorithms used are proprietary and I'm unable to share exactly how the DATAx values are calculated. However, this is not a necessary step to use the LDC2114. You do not need to design your system to achieve a specific change in DATAx when the button is pressed, because you can use the GAINx settings to increase the DATAx values if necessary. Instead of designing your system to achieve a specific DATAx value, design your system to have a strong inductive response, which you can do by following the steps listed in the documents.

Best Regards,

Hello, Ms. Jones

Thank you for your reply.
I understood what you are saying.
The most appropriate method is to adjust GAINn according to the actual button sensor.
LDC2114 adopts a groundbreaking system in a sense doesn’t it?.
I'll try for now.
I will contact you later.

Best regards.

Thank you for your reply.

I understood what you are saying.

The most appropriate method is to adjust GAINn according to the actual button sensor.

LDC2114 adopts a groundbreaking system in a sense doesn’t it?.

I'll try for now.

I will contact you later.