KW41Z - Power Consumption

[jianalai]

Based on the datasheet, the power consumption of KW41Z in VLLS1 buck mode as shown as below. May i know under what condition to achieve this results? What are the configuration for the GPIOs (pull low/pull high, input/output and etc.) and clock before enter VLLS1?

Attached is my schematic, I have measured at VBAT point and got the power consumption around 14uA. It is quite much different compare with the spec from datasheet. Am I measured at the correct point?

[gerardo_rodriguez]

Hello Jia Na Lai,

Sorry for the delay.

You are correct, J18 is needed for programming because it provides voltage to P3V3_BRD and enables the debugging lines, but this means that the current will increase, so it needs to be removed for measuring current.

About the smac_low_power_node example, are you testing the low power modes with the [1] Manual Power Modes Configuration from the main menu? I believe the pins are not handled automatically in this test. I modified the code to prepare the pins before entering VLLS modes. I reused the BOARD_EnterLowPowerCb() from board.c and added it just after the gLPDMStateEnterLowPower_c: case inside the ManualLPMScenario() function. With this I am able to measure similar currents as the BLE demo in a FRDM-KW41.

About your last question, can you share how and where are you entering low power? I need to reproduce this behavior so I can investigate why you need a delay to enter the low power mode successfully.

[jianalai]

Hi,

Thanks for your support. You can download the project file which i have modified from the following link.

Dropbox - frdmkw41z_wireless_examples_smac_low_power_node_freertos_modified.zip 

I must put either one of the function (OSA_TimeDelay() or PWR_CheckIfDeviceCanGoToSleep()) just can prevent the SACKERR.

Pls help me to investigate why i need a delay to enter the low power mode.

Thanks. 

[gerardo_rodriguez]

Hello Jia Na Lai,

To reach the current reported by the datasheet you must take care that all your pins are in the disabled state (mux 0) to prevent unwanted leakage (potentially caused by floating inputs). You can refer to the chapter 2.6 Kinetis Energy Savings – Tips and Tricks from the Power Management for Kinetis MCUs AN4503 application note for more tips on how to reduce unwanted current.

Best regards,

Gerardo

[jianalai]

Hi,

Can you provide the sample code that will demonstrate shutdown to below 2uA when the KW41 enters VLLS1. 

[gerardo_rodriguez]

Hello Jia Na Lai,

The easiest way of testing this would be to run an example from the SDK such as the BLE heart rate sensor demo. This demo has low power support enabled by default and uses the DCDC in buck mode. The only difference is that this demo enters LLS3, but can be easily changed so that it enters VLLS1 instead. 

Change the deep sleep mode from 3 to 4 in PWR_ChangeDeepSleepMode() inside BleApp_Config() in heart_rate_sensor.c. This way, the demo will enter VLLS1 after the initialization is complete. A description of the power modes supported by the connectivity framework can be found at chapter 3.15.4.3 Deep sleep modes from the "<SDK>\docs\wireless\Common\Connectivity Framework Reference Manual.pdf" document. Please note that the recovery from VLLSx modes is through a reset sequence and is not handled by the demo. Also, make sure that you are using the latest KW41 SDK from the MCUXpresso builder.

With this configuration I was able to measure ~1.3µA in a FRDM-KW41Z. For measuring low power current on buck mode on the FRDM-KW41Z, you need to consider point 3 of the document FRDM-KW41Z Development Platform Errata. Since there is a pull up resistor that can prevent measuring the low power datasheet numbers. See below my jumper configuration so you can replicate the measurement. 

Let me know if you have any question or issue.

Regards,

Gerardo

[yaoxingshan]

Hello, I used the LPED example in the FRDM-KW41 SDK and measured the power consumption according to your diagram. I found that it is up to 10mA. Is there a problem?

[jianalai]

Hi,

Thanks for the info. With the BLE heart rate demo, on our board, are able to get about 1uA when entering VLLS1. When we try on the FRDM-KW41, with J18 remove as shown in the photo, we cannot get the JTAG/debug to work, we need to insert J!8 to program and remove it to measure the current, is this correct?

We are working on sdk example wireless_example_smac_low_power_node, the power consumption is 16uA on our board.

We also tried to disable the port pins used in the code (mux=0) but the currrent still remains at 16uA Please advise where should we look at to get the same current consumption as the BLE heart rate demo. 

Another question i have modified the code and why i cannot direct enter to low power mode need to put some delay just can enter to low power mode successfully else will get the SACKERR.