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Constant “10” in the Fsw(max) equation - KBA234212

Constant “10” in the Fsw(max) equation - KBA234212

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Constant “10” in the Fsw(max) equation - KBA234212

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The maximum sense clock frequency [Fsw(max)] is calculated as follows:

KBA234212.PNG

 The selected sense clock frequency should be such that the sensor will charge and discharge completely in each sense clock period. The equation for the maximum sense clock frequency comes from the characteristics of the RC circuit.

In an RC circuit, it takes about 5 RC until the capacitor is completely discharged. Because the discharge is performed in half the time of one cycle, the time of one cycle is T = 2 * 5RC = 10RC; the frequency is calculated as 1 / T; therefore, it is 1/10 RC.

See AN85951 – PSoC™ 4 and PSoC™ 6 MCU CAPSENSE™ design guide for more information.

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