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nPM1100 Operation

fmighani

We are using nPM1100 along with a STM CPU. When we put the CPU into deep sleep, it takes one minute for the current to go down to 20uA from 500uA.

We were expecting the nPM1100 goes down to low load mode right away not after 1 minute.

The question is, does nPM1100 need the 1 minute to detect low-load to drop the current?

Please advise.

Thanks.

Kind Regards,

Farhad Mighani 

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  • 0 in reply to runsiv

    Hi Farhad

    Could you clarify a bit regarding your setup. As of now I have the following questions:

    1. Is it a battery only system?

    2. Are you using 

    3. Are you using the DCDC buck to supply your MCU, if so what is the battery voltage, buck output voltage and what is the mode of the buck, automode or forced PWM?

    Regards

    Runar

  • 0 in reply to runsiv

    Hi Runar,

    Thanks for getting back to me.

    We are using nPM1100 to generate 1.8V to feed the MPU. We have both options to feed nPM1100 from a battery or USB interface. When we put the MPU into deep sleep, it is powered via the USB interface (wall powered).

    Please see below the configuration to answer some of your questions. I hope this helps to help us! Thanks. Kind Regards, Farhad

  • 0 in reply to fmighani

    Thanks for the information. 
    I have forwarded the information internally and will get back to you as soon as I have something

    Regards

    Runar

  • 0 in reply to runsiv

    Update 

    If you are supplying from VBUS input, then when in low current the DCDC might go in low power mode. But the rest of the chip is still requesting biasing current and references for the VSYS regulator and the battery charger to operate. So it seems normal to us to keep current consumption around 500uA. It is surprising it goes down to 20uA after 1 minute.So i'm asking internally if they have input.

    Edit: 

    Do you have any information regarding the voltage variations on VBAT, VBUS, or VSYS? 

    Regards

    Runar

  • 0 in reply to runsiv

    Thanks.

    We have left NTC open. Therefore, there should not be any battery charging going on.

    We feed nPM1100 from USB and there is no battery in the system. USB input is 5V. I suspect that VSYS is at 5.0 (we will measure). 

    When we are in deep sleep, we draw only 10uA. so, we are in low load mode for sure. According to the datasheet, in low load mode, nPM1100 quiescent current can be as low as 800nA (.8uA). we expect the nPM1100 to detect the low load and drop to what is needed (around 10uA-17uA). Do we need to run this in PWM mode for low load detection to take effect right away?

    This is very important to us. That is why we picked this device.

    Is it time to have a conf call?

    Thanks.

    Kind Regards,

    Farhad   

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