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PSoC™ 4

masu_1341616
New Contributor II

I can see on your reccomendation of "General layout guideline of CY8CMBR3xxx_Design_Toolbox.xlsx" .

Our Proximity Spec

- Proximity Loop diameter      19mm

- Required Proximity Distance  19mm

Guideline

Proximity sensor Parasitic Capacitance (Cp)

Min 8 pF -- Max 45 pF

I input our parameter to "Table B: Cp Calclator of CY8CMBR3xxx_Design_Toolbox.xlsx".

This resuilt 6pFis out of your recommendation.  6pF < min 8pF

If you have any concern about this result. Please advice to avoid issue.

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1 Solution
Hari
Moderator
Moderator

Hi masu_1341616

Since MBR3 device uses smartsense algorithm for tuning, it is recommended to ensure that Cp criteria is met.

In the layout, you can leave a jumper to add a parallel capacitor in the proximity sensor trace if needed. This will ensure that Cp (parasitic capacitance) is added to the pin as observed by the MBR3 device and allows setting the parameters accordingly. In a prototype of the layout, if the sensor is not working as expected due to small Cp, the parallel cap will help adjust the capacitance.

Best regards

Hari

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4 Replies
Hari
Moderator
Moderator

Hi masu_1341616

Since MBR3 device uses smartsense algorithm for tuning, it is recommended to ensure that Cp criteria is met.

In the layout, you can leave a jumper to add a parallel capacitor in the proximity sensor trace if needed. This will ensure that Cp (parasitic capacitance) is added to the pin as observed by the MBR3 device and allows setting the parameters accordingly. In a prototype of the layout, if the sensor is not working as expected due to small Cp, the parallel cap will help adjust the capacitance.

Best regards

Hari

View solution in original post

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masu_1341616
New Contributor II

Hello Hari,

Thank you for your help.

I have aquestion about the parallel cap.

Does it have to connect to loop sensor and GND?

Do you have any advice about pattern layout? I will layout this pattern near by MBR3 IO.

Best Regards,

Masa

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Hari
Moderator
Moderator

Hi Masa-san,

Yes, the Capacitor needs to be connected to the loop sensor and ground. This need not be connected always and is required only if you observe poor sensor performance.

The parallel capacitor needs to be placed after the 560 ohm series resistor.

For the proximity sensor, the general guidelines need to be followed. A 1.5 mm thick sensor trace forming a loop will act as a proximity sensor. Providing a ground loop around the proximity sensor will help in improving noise performance.

You can also refer MBR3 CapSense design guide for more details.

Best regards

Hari

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masu_1341616
New Contributor II

Hello Hari-san,

Thank you for your answer. I update the design.

Best regards,

Masa

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