nPM1100. From were this current is coming?

[p143]

Hi All.
I am using your NPM1100 PMIC as part of an IoT project in which low consumption is a critical restriction. The PMIC is working as expected, but there is a detail I don't understand. Once the charging cycle is completed and the green LED gets off, there is a remaining consumption of 1,7 to 1,9 mA through the VBUS, even if I disconnect the charged battery from VBAT and the secondary load from VOUTB. All this happens with the SW1 switch set to automatic, and If I set it to PWM -still with the secondary load disconnected-, the leak current goes even higher till 5,5 mA.
Could you tell me where this current is coming from? Can I be sure that this current won't load the battery, diminishing the module power autonomy once the primary charging power gets disconnected from VBUS?

Thanks

[Stian Røed Hafskjold]

Hi Juan,

I believe this VBUS current is normal when the USB cable is connected (VBUS voltage applied) as it powers up the battery charger etc (even though a battery is not connected). So I'm not sure if this power domain is power optimized, since VUBS current consumption is usually not an issue. However, when VBUS is disconnected, the quiescent current should be very low, since it is now running from the battery. I will do some measurements in the lab and ask the design team to confirm if this is correct or not, and get back to you shortly!

Best regards,
Stian

[p143]

Hi Stian,

Please. Check the schematics I sent to Priyanca. The nPM1100 EK is consuming 1,7 mA through Vbus while it is not loaded through VBAT, VSYS or VOUTB, and this is happening even with both LEDs disconnected. This is not dramatic, but it must be understood, because if it also happens while the battery is fully charged and takes command of the feeding (through VOUTB in my case), then 1,7mA would dramatically affect the battery autonomy, so let's wait for these lab measurements. 

Best regards,

Juan

[Stian Røed Hafskjold]

Hello!

I checked with measurements, and VBUS will consume 2mA while connected. This is current consumed inside the chip. When VBUS is disconnected the nPM1100 enters low power mode and the draw from the battery is about 800 nA when no other load is connected to VOUTB or VSYS.

The low power mode is described here: https://infocenter.nordicsemi.com/topic/ps_npm1100/product_overview.html?cp=7_0_0_2_1#system_desc

When VBUS is disconnected, SYSREG ensures the device enters Ultra-Low Power mode to minimize quiescent current

And here: https://infocenter.nordicsemi.com/topic/ps_npm1100/chapters/core_components/sysreg/doc/frontpage.html?cp=7_0_0_5_0_3#concept_vbus_disconnect

Here are some measurements showing the VBAT and VBUS current before and after VBUS is disconnected:

VBUS=5V

VBUS=0V

Best regards,
Stian

[p143]

Thanks, Stian.