MKL03Z: High Current Consumption in Low Voltage Conditions

[gauravbanyal]

I have a question about low voltage operation of the MCU.

In my application, when the MCU is in VLLS0 state (consuming around 0.1uA) and the supply voltage (Vbatt) is reducing gradually, somewhere in the vicinity of 1.2v, the current consumption of the MCU shoots up in the mA range and doesn’t go to the nA range again and the battery is completely discharged.

In the reverse path, when the battery voltage is gradually increased from 0V, the current consumption is in the mA range and around 1.9v, the current consumption again goes to around 0.1uA (VLLS0).

We want to avoid this high current draw from the MCU when the supply voltage is under these ranges. Is there a software setting for avoiding this? I think the LVD can help only when the device was in RUN mode and not in VLLS0. Is there a way?

Thanks and best regards,

Gaurav Banyal

[jorge_a_vazquez]

Hi Gaurav Banyal

According to your description, this is a normal behavior. When the supply voltage drops below the VPOR (1.1V for KL03), the POR circuit causes a reset condition. With this reset your MCU recover from VLLS and get in RUN mode, but LVD circuit holds the MCU in reset until the supply rises above the LVD low threshold VLVDL (1.6V), which will allow your MCU to execute code normally and allow you to get in VLLS again.

As you mentioned LVD system is Off in VLLS, so for this mode you will have to periodical check your battery voltage to avoid that it drops below Vpor.

Have a great day,
Jorge Alcala

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[gauravbanyal]

Well if this is the behavior the chip has, thats how it is.

I would just like to comment that this is not good design.

It might be worthwhile to send this feedback to your chip designers that outside of the allowed voltage ranges, the chip should not consume any power. 

Thanks for your response.

Best regards,

Gaurav.

[jorge_a_vazquez]

Hi Gaurav Banyal

Thanks for your feedback, I will share your comments to the development team. Sorry for the inconveniences that this may cause you.

Regards

Jorge Alcala