Cmod voltage wave from CY3280-BK1 board

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befic_2639911
Level 2
Level 2
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hello,every one.

          I captured the Cmod voltage wave from CY3280-21x34 at the CY3280-BK1 board,just as below.csd.png

While according to 《Cypress’ CapSense Sigma-Delta Algorithm》,the wave should  like this.

          cmod.png

they are very different.

how to explain the Oscilloscope wave?

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1 Solution
BragadeeshV
Moderator
Moderator
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First question asked 1000 replies posted 750 replies posted

Hi beyows_2639911​,

CY8C21X34 uses first generation CSD structure( with Rbleed resistor). In this structure, Vref connected to delta-sigma comparator is adjustable based on the component config (Reference and Ref Value parameter). Hence CMOD voltage not being equal to 1.2 V is expected.

CMOD pin will be shorted to GND to fully discharge. Hence the negative pulse, at the end of each scan cycle is also expected.

Regards,

Bragadeesh

Regards,
Bragadeesh

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BragadeeshV
Moderator
Moderator
Moderator
First question asked 1000 replies posted 750 replies posted

Hi beyows_2639911​,

CY8C21X34 uses first generation CSD structure( with Rbleed resistor). In this structure, Vref connected to delta-sigma comparator is adjustable based on the component config (Reference and Ref Value parameter). Hence CMOD voltage not being equal to 1.2 V is expected.

CMOD pin will be shorted to GND to fully discharge. Hence the negative pulse, at the end of each scan cycle is also expected.

Regards,

Bragadeesh

Regards,
Bragadeesh
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