Cypress CapSense CY8CMBR2044, Руководство по конструкции

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CapSense Schematic Design
AN66308 - CY8CMBR2044 CapSense® Design Guide, Doc. No. 001-66308 Rev. *F 27
C
P
, Power Consumption and Response Time Calculator
After the board layout has been completed, use this calculator to check the design before building the button board
prototype. To verify the C
P
value of each button, insert the button diameters and trace lengths into Table A. After you
enter the information, the toolbox confirms whether each button is within the specified C
P
range of 5 pF to 40 pF. The
power calculator in Table B is used to optimize power consumption. Power consumption is a function of the button
scan rate, which is set by the resistor value on the ScanRate/Sleep pin. Refer to
Section 3.4 Scan Rate and Table
3-4 . Table C outputs the button response time based on the inputs in Tables A and B.
Figure 3-14. C
P
, Power Consumption and Response Time Calculator
Inputs:

Button diameter and trace length of CS0
–CS3 as designed in layout

Button Scan rate resistor value

The percentage of time a finger is on the buttons
Outputs:

Parasitic Capacitance (C
P
) for each sensor. Confirms whether the C
P
values are within the specified range
of 5 pF to 40 pF

Power consumption per button

Button response time
After you have built and tested the prototype board, you can determine the actual parasitic capacitance (C
P
) and
noise condition (noise count) of each button according to the Section 3.1.10 Serial Debug Data Out . Use this
information and the Design Validation Sheet to validate the design, as detailed in Section 0Design Validation