High Current in IDLE

[Hermano Guimaraes]

Hello.

We are implementing npm1100 in our project. I'm measuring about 4mA without any load connected.

Please see circuit below:

Did I made anything wrong?

Thanks.

[Kazi Afroza Sultana]

Hello,

Your schematic looks ok.

I have measured VBAT current without any load and it was 4.6 MA. Then I try to enter ship mode by pressing SHPACt button, which reduces the current to 0.47 uA. 

Ship mode isolates the battery, reducing quiescent current. To enter Ship mode, SHPACT must be set high for a minimum period of t_activeToShip when VBUS is disconnected and SHPHLD held high (V_IH) (https://infocenter.nordicsemi.com/topic/ps_npm1100/product_overview.html?cp=7_0_0_2_4#ship_mode). 

Thanks.

BR

kazi

[Hermano Guimaraes]

Hello Kazi.

In the datasheet the typical quiescent current is 800nA. This is correct?
My application need a very low quiescent current. Today I use a regulator that drain 1.9uA, I was hoping that npm1100 had a better performance.

Is npm1100 suitable for my application?

Thanks

[Hermano Guimaraes]

Today I'm using TPS7A0233PDBVR regulator.

My circuit is draining 900uA while running and 16uA in sleep mode, I don't have shipping mode at the moment, this is one of the drivers for my change to npm1100.

In sleep mode the regulator drains 1.9uA, nrf52832 drains 280nA, accelerometer 9uA and A/D converter 300nA. The others components drain the rest.

I measured this currents with a precision true RMS multimeter and with a oscilloscope, both with same results.

My goal is to repleace the regulator and battery charging circuitry for npm1100 without increasing the current drain.

[Kazi Afroza Sultana]

Hello,

Looking at your schematic once again I can see MODE pin is connected to VSYS. Setting MODE to VSYS causes the BUCK to operate in PWM mode.  This causes extra current consumption (4.5mA) (unfortunately not quite well documented in PS) (https://infocenter.nordicsemi.com/topic/ps_npm1100/chapters/core_components/buck/doc/frontpage.html?cp=7_0_0_5_2_1#buck_mode_selection)

Ship mode isolates the battery, reducing quiescent current. If using SHIPMODE feature, SHPHLD cannot be connected to VSYS because VSYS is 0V in SHIPMODE and it will wake-up the device. Instead, it must be connected to VBAT through a pull-up resistor. See https://infocenter.nordicsemi.com/topic/ps_npm1100/chapters/application/doc/frontpage.html?cp=7_0_0_6_6#unique_2037983651 

To enter Ship mode, SHPACT must be set high for a minimum period of time (200ms) when VBUS is disconnected and SHPHLD held high. 

There are two ways to exit Ship mode. Either connect the USB (VBUS) or set SHPHLD low for a minimum period of 200ms. The battery supply (VBAT) is used to hold SHPHLD high through a weak pull-up resistor when Ship mode is enabled. 

If Ship mode is not required, then SHPACT and SHPHLD pins may be tied to AVSS.

[Hermano Guimaraes]

Hi

If I use Hysteretic Mode my radio performance will be affected?
How is the consumption for this mode?

[JONATHAN LL]

Hermano Guimaraes said:

Hysteretic Mode my radio performance will be affected?

It should not be. 

Hysteretic modes for low load currents(90mA/40mA), but it is not possible to lock the device to use only Hysteretic mode. It will automatically switch to PWM if load currents demand it. 

You can see the data shown here: https://infocenter.nordicsemi.com/topic/ps_npm1100/chapters/core_components/buck/doc/frontpage.html?cp=7_0_0_5_2_4#elec_chara 

Regards,
Jonathan

[Hermano Guimaraes]

Hi Jonathan,

My circuit drain 780uA so I changed the configuration to Hysteretic mode and didin't affect my radio performance. The voltage looks clean in the oscilloscope even switching the strain gauges.

In this mode the npm1100 is draining 900nA without load, very close to the datasheet. Now is working fine for me in terms or current consumption.

The only issue that I'm having right now is the PCB layout, I have such small space to work, but that is another topic.

Thanks,

Hermano