Very high power consumption with CapSense Module (250uA instead of 6uA)

[DiRa]

Hi,

I tried to run the "CE210291 - PSoC® 4 CapSense® Low-Power One Button" example on our own hardware. This is a CY8C4025LQI-S411 with only the necessary components around.

Tooling: PSoC Creator 4.4  +  Kitprog2
Current measurement with a multimeter (Voltage on a 10Ohm resistor) and with an optical separated differential frontend with an oscilloscope.

When I run the sample code and measure the current consumption I measure 250uA. This is far more than the expected 6uA.

I tried out several things:

With and without connection to the I2C
Power only
Call CySysPmDeepSleep() at the begin of main()
Call CapSense_Start(), CapSense_CSDSetupWidgetExt(), CapSense_Sleep() in front of CySysPmDeepSleep()
Delete CapSense and/or EZI2C fron the “TopDesign.cysch”
Only the last try (without the CapSense module) the current was less than 10uA which was in the expected range.

The only thing I change from the example was the controller type and the pinning.

Can you give me a hint why initializing the CapSense module give me an offset of about 250uA and how I can get rid of it?

Our target is reading 9 keys every 30ms via I2C with a average current of less than 200uA which I think should be possible regarding the data-sheet.

Best regards and thank you in advance,

Dirk

[Hari · Accepted solution]

Hi @DiRa 

Please note that the CE210291 - PSoC® 4 CapSense® Low-Power One Button code example moves to a slow-scanning mode only if the sensors are not active. So, can you please make sure the sensors are not active while measuring the current consumption?

A few other points to consider - 

 - Please make sure that the debug interface is disabled while measuring the current consumption. This can be done by going to Design Wide Resources > System > and changing the SWD pins to GPIO instead of SWD. This will disable the debug block. 

Also, in the same window, please make sure you set the right VDDD and VDDA voltage levels. 

 - Check if the system is actually entering deep sleep mode - this can be done with the help of an LED. You can turn off the LED whenever the system is in debug mode and turn it on immediately after. This will make sure that the PSoC is indeed entering deep sleep mode. 

Best regards, 
Hari

[DiRa]

Hi Hari,

thank you for your fast reply.
The VDDD was the problem. I never measured the voltage that came from the KitProg2. It is 5V and the setting was 3,3V. After changing that to 5V I measure 5uA in slow and 16uA in fast mode (with a low cost multimeter at home).
Till I didn't start the scanning at all (go to deep-sleep at beginning of main()) and already set the SWD pins to GPIO, this was the only thing you mentioned and that was it.

Good start in the weekend 😉

Thank you and best regards,

Dirk