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PSoC 5, 3 & 1 MCU

Honored Contributor

Hi,

We would like to confirm for CapSense CSD component of PSoC5LP.

From the CapSense datasheet excerpt,

RawcountVsVcc.JPG
We understand that the sensitivity changes when the supply voltage changes.

What is this "supply voltage" dependent on?

1. VDDA

2. VDDD

3. VDDIO (GPIO use d in CapSense sensor)

4. All the above

Because the sensitivity changes due to the fluctuation of the power supply voltage,
We are considering using LDO.
So, we would like to know which voltage to care for.

Regards,

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1 Solution
Moderator
Moderator

Hi,

The CapSense IP uses IDACs which are directly connected to the VDDA supply. Therefore there will be slight variation in raw counts due to variation in VDDA because of IDAC characteristics.

If you are using IDAC sinking mode, the sensors are directly switched by VDDD so the sensitivity changes in this case when VDDD changes. There will not be any dependency on VDDD if you use IDAC sourcing mode.

Finally, I would like to say that if the SNR is greater than 5 through out the voltage range, there will not be any problem.

Thanks

Ganesh

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2 Replies
Moderator
Moderator

Hi,

The CapSense IP uses IDACs which are directly connected to the VDDA supply. Therefore there will be slight variation in raw counts due to variation in VDDA because of IDAC characteristics.

If you are using IDAC sinking mode, the sensors are directly switched by VDDD so the sensitivity changes in this case when VDDD changes. There will not be any dependency on VDDD if you use IDAC sourcing mode.

Finally, I would like to say that if the SNR is greater than 5 through out the voltage range, there will not be any problem.

Thanks

Ganesh

View solution in original post

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Honored Contributor

Ganesh-san,

Thank you for your response.

I understood that it depends on VDDA and VDDD, and only VDDIO has no effect.

Consider the use of LDO because the VDDA voltage fluctuation is severe.

Regards,

Masashi

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