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NaMo_1534561
Level 5
Level 5
Distributor - Macnica (Japan)
100 replies posted 100 sign-ins 50 replies posted

Hello,

What is the modulation rate(%) or modulation frequency of spread spectrum of Fourth-generation CapSense in each setting of SSC6, SSC7, SSC9 and SSC10?

Also, is the modulation rate the center spread or down spread?

Best Regards,

Naoaki Morimoto

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1 Solution
Hari
Moderator
Moderator
Moderator
750 replies posted 500 replies posted 250 solutions authored

Hello NaMo_1534561

SSC does not "modulate" the sense clock. It only spreads the clock frequency based on an LFSR. The spread spectrum frequency range must be within +/-10% of the sense clock frequency. This is taken care by the component and the component will allow you to choose the value only if this condition is satisfied. Please refer the component datasheet for details on the conditions required to be satisfied while choosing SSC.

Spread spectrum is center spread with center frequency equal to the sense clock frequency set in the component.

Best regards

Hari

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3 Replies
Hari
Moderator
Moderator
Moderator
750 replies posted 500 replies posted 250 solutions authored

Hello NaMo_1534561

SSC does not "modulate" the sense clock. It only spreads the clock frequency based on an LFSR. The spread spectrum frequency range must be within +/-10% of the sense clock frequency. This is taken care by the component and the component will allow you to choose the value only if this condition is satisfied. Please refer the component datasheet for details on the conditions required to be satisfied while choosing SSC.

Spread spectrum is center spread with center frequency equal to the sense clock frequency set in the component.

Best regards

Hari

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NaMo_1534561
Level 5
Level 5
Distributor - Macnica (Japan)
100 replies posted 100 sign-ins 50 replies posted

Hello Hari-san,

In the CSD (Self-cap) setting, the switching signal period on the sensor measured under the following conditions was 21.12us to 21.24us.

SSC7

Resolution 14bit

Modulation Clk 24000KHz

SnsClk 46.88KHz

It looks like it is the same as the Direct waveform.

Are there any other settings required to enable SSC?

Best regards,

Naoaki Morimoto

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Hari
Moderator
Moderator
Moderator
750 replies posted 500 replies posted 250 solutions authored

Hi NaMo_1534561

There are two conditions that need to be satisfied for SSC to take effect.

1. pastedImage_0.png

2. pastedImage_1.png

In the present configuration, condition 2 is not getting satisfied, as resolution, N = 14, mod clock = 24000kHz, SSCN = 7 and snsclk = 46.88.

Please make sure that the configuration satisfies the condition so that the component sets SSC correctly. If this condition is not satisfied, the component switches to Direct by default.

Best regards

Harigovind

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