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PSoC 4 MCU

YoIs_1298666
Contributor II

Hello,

We know that the "CE210291 - PSoC® 4 CapSense® Low-Power One Button" project transitions between Deep Sleep and Active mode to achieve CapSense with low power consumption. When the Deep Sleep current is measured using CY8CKIT-041-40XX with the power supply voltage set to + 3.3V, it is several μA.

On the other hand, when the Deep Sleep current is measured with the power supply voltage set to + 5 V and the VREF set to 2.021 V, approximately 350 μA is consumed.

YoIs_1298666_0-1612924532686.png

Do we need to put VREF to sleep before executing CySysPmDeepSleep ()?

 

If the power supply voltage is + 5V and the Vref is 2.473V, the Deep Sleep current will be several μA.

YoIs_1298666_1-1612925226802.png

We would like to adjust the gain of raw count value with Vref.

YoIs_1298666_2-1612925447825.png

Best regards.

Yocchi

 

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Hari
Moderator
Moderator

Hello Yocchi-san, 

 

This is not recommended. Latest generation CapSense has an internal voltage measurement circuit that tries to set the VREF according to the actual voltage level instead of the one set in PSoC creator. The conflict between these two might be the reason for the increased current draw. It is always recommended to set the VDDD and VDDA according to the actual operating parameters. 

 

Best regards, 
Hari

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Hari
Moderator
Moderator

Hello Yocchi, 

 

You do not have to set the VREF to sleep during a low power transition, but it is recommended to set the operating conditions equal to whatever you have on the board. 

If you are operating in 3.3V, the VDDD and VDDA are recommended to be set to 3.3V. Note that you will observe the same current consumption even if you disable CapSense, indicating the independence of VREF on the current consumption. 

 

Vref is strictly dependent on the operating voltage and is not recommended to be used as a parameter to adjust the gain. You can adjust the IDAC gain to obtain a lower IDAC code for better gain (for CSD it is recommended to have an IDAC code of 18 or greater). 

 

Best regards, 
Hari

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YoIs_1298666
Contributor II

Hello Hari-san,

Thank you for your reply.

If I don't set it to DeepSleep mode, can I change the VREF like KBA220609?

https://community.cypress.com/t5/Knowledge-Base-Articles/VREF-of-PSoC-4-CapSense-Component-KBA220609...

YoIs_1298666_2-1613628509270.png

 

Does that mean that if I use DeepSleep mode, I should only use the settings painted in red?

YoIs_1298666_1-1613628449595.png

 

Best regards,

Yocchi

 

 

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Hari
Moderator
Moderator

Hi Yocchi-san, 

 

The CapSense component sets the VREF based on the VDDA on its own. This need not be set by the user. So, if your design has VDDA = 3.3V, the VREF that would be chosen for the sensor is 2.1V and if VDDA = 5V, then VREF would be 2.743V. There is no dependency on Deepsleep. 

The current consumption does not increase with lower VDDAs - I tried it on a 145-40XX kit (which has the same IC), powered it externally so that kitprog is not activated and with CapSense and VDDA = 3.3V, the current that I was seeing in DeepSleep mode was 16uA. 

 

Best regards, 
Hari

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YoIs_1298666
Contributor II

Hello Hari-san,

Thank you for your reply.

 

If Auto Calibration is turned on, it was observed that changing the VREF would change the IMOD and ICOMP values in the same direction and adjust the RawCount value to 85%.

Therefore, if we are conscious of setting the IDAC code to 18 or larger, I feel that it is better to have a large VREF.(Of course, it depends on the parasitic capacitance.)

YoIs_1298666_0-1613960820217.png

I have one question here.

Q1:Does the IDAC code of "an IDAC code of 18 or greater" mean an IMOD code?

 

Well, The following does not apply. If we set VDDA=5V, the current is about 5.0uA. 

And if we set VDDA=3.3V, it will be 387uA. I attach the project.

This project has been modified so that LED1 turns on when touched.

> The current consumption does not increase with lower VDDAs - I tried it on a 145-40XX kit > (which has the same IC), powered it externally so that kitprog is not activated and with

> CapSense and VDDA = 3.3V, the current that I was seeing in DeepSleep mode was 16uA. 

 

Best regards,

Yocchi

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Hari
Moderator
Moderator

Hello Yocchi-san, 

 

Q1:Does the IDAC code of "an IDAC code of 18 or greater" mean an IMOD code?

Yes, the IDAC code I am referring to here is the Modulator IDAC code in the component/tuner. 

 

I tried the same project - the only change being the VDDD and VDDA in the systems tab set to 3.3V and I am still observing a current draw of only 10-12uA. This is when there is no activity in CapSense and the system switches to slow scan mode with deepsleep. 

 

Please check the tuner and make sure that the CapSense sensors are not false triggering.

Also, during the current measurement, please make sure that the tuner is not active and the LEDs are off. 

 

Best regards, 
Hari

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YoIs_1298666
Contributor II

Hello Hari-san,

Perhaps the CY8CKIT-145-40XX's P4_ VDDD supply voltage is much lower than + 5V.

YoIs_1298666_0-1613981648086.png

Best regards,

Yocchi

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Hari
Moderator
Moderator

Hello Yocchi-san, 

 

So you are trying VDDD of 5V, VDDA of 3.3 where the current draw is higher?
Can you try a simpler project without CapSense to see the current draw without the effect of VREF?

 

Best regards, 
Hari

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YoIs_1298666
Contributor II

Hello Hari-san,

> So you are trying VDDD of 5V, VDDA of 3.3 where the current draw is higher?

The power supply VDDD for PSoC4000S is 5V and the operation condition in system of PSoC Creator is 3.3V.
 
The result with VDDD of 5V, VDDA of 3.3 is attached.
YoIs_1298666_0-1614213016925.png

Best regards,

Yocchi

 
 
 
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Hari
Moderator
Moderator

Hello Yocchi-san, 

 

This is not recommended. Latest generation CapSense has an internal voltage measurement circuit that tries to set the VREF according to the actual voltage level instead of the one set in PSoC creator. The conflict between these two might be the reason for the increased current draw. It is always recommended to set the VDDD and VDDA according to the actual operating parameters. 

 

Best regards, 
Hari

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YoIs_1298666
Contributor II

Hello Hari-san,

 

I agree with you.

I have the last question.

If I do not use the deepsleep mode and use only active mode, is it okay to set VDDD and VDDA that are different from the actual PSoC power supply voltage?

 

Best regards,

Yoccchi

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Hari
Moderator
Moderator

Hello Yocchi-san

 

I would not recommend doing that, especially if you have shield in the application. The reason is that the CapSense sensors have an internal voltage measurement circuit that tries to set the voltage according to the actual VDDA whereas, the shield depends on the value set in the design wide resources. This will lead to a difference in the voltage level of the sensor and shield that will increase the noise and limit the liquid tolerance. 

 

Hence, as a best practice, I recommend setting the right VDDA and VDD for all projects. 

 

Best regards, 
Hari

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YoIs_1298666
Contributor II

Hello Hari-san,

I agree with you.

KBA220609 should be set to the actual power supply voltage.

Best regards,

Yocchi

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