nPM1100 questions and observations

[DBT]

We want to understand any surprises with using nPM1100 on existing or future products.

I just bought two nPM1100-EK units and finished the first round of my evaluation.

Here is a summary of my findings and questions:

1. Pressing the SHPACT button with VBUS present:  Section 3.5 of the nPM1100 datasheet "Using Ship mode" leaves the impression that ship mode won't be activated unless VBUS is discharged below VBUSmin.  Based on testing, it looks to me like pressing the SHPACT button enters ship mode regardless of the voltage on VBUS.  It's just that you will immediately exit shipmode when VBUS is high (that's one of the two ways to exit shipmode).  Activating shipmode while VBUS is high will effectively powercycle whatever VOUT is connected to.  The datasheet should be more clear.

2.  Battery charge threshold 2.1V:  If the battery voltage is < 2.1V when VBUS goes high, the nPM1100 will not start charging and signals a FAULT.  Our battery pack currently as a protection chip built into it that will disconnect the external load from the cell if the cell voltage drops below 2.8V, so the external voltage seen by the nPM1100 becomes 0V.  Is it correct that if our battery gets into this state, the nPM1100 will never charge it?  This is important because our device isn't meant to be opened, so if the battery over-discharge circuit kicks in, this feature will "brick" our device.

3. Static inputs (VTERMSET, ICHG, VOUTBSETx): In the nPM1100 datasheet, section "3.1.1 In circuit configurations" states "Static input pins must be configured before power-on reset." I thought this meant that if you changed the polarities of these pins after reset, it would have no effect, but I found in testing that when I changed these after reset they still took effect (VTERM, ICHG and VOUT would all change at the moment I changed the switch positions on the nPM1100-EK board).  Is there some reason these pins should not be changed dynamically?  The datasheet should be clear about what should not be done vs what will have no effect.

4. POR: Datasheet section "3.3 Power-on reset (POR) and brownout reset (BOR)" states "VBATPOR has a minimum and maximum range. To ensure the device exits reset, the voltage should be above the maximum of the parameter." but Table 15 only gives a typical value of VBATpor, not max/min values.

[Bendik Heiskel]

Hi again,

Sorry for the delay.

Is it correct that if our battery gets into this state, the nPM1100 will never charge it? 

There is a battery detection phase at the beginning of the charge, this should rise the voltage on VBAT pin above 2.8V to trigger the protection and close the protection device.

Is there some reason these pins should not be changed dynamically? 

Changing these pins dynamically may have an effect. But there is no guarantee changing these after power-on reset won't introduce unwanted behavior.

4. POR: Datasheet section "3.3 Power-on reset (POR) and brownout reset (BOR)" states "VBATPOR has a minimum and maximum range. To ensure the device exits reset, the voltage should be above the maximum of the parameter." but Table 15 only gives a typical value of VBATpor, not max/min values.

The maximum value for VBATPOR is 2.8V

 

Best regards,

Bendik

[DBT]

Please clarify the "battery detection phase" behavior.

Assuming the cell voltage and pack voltage are >=2.8V, charging will start as expected.

If cell voltage = 2.1V (pack voltage = 0V) the battery detection phase will apply some minimal charge current to the battery, see the 2.1V and continue charging?

If cell voltage < 2.1V (let's say its 1.5V) (pack voltage = 0V) the battery detection phase will apply some minimal charge current to the battery, see the 1.5V and disable charging?

[Ecic2002]

We are currently evaluating the nPM1100 for a new design. Did you ever receive an update from Nordic regarding this issue?

[DBT]

No, I didn't get answers beyond what is here, but at that point we had decided not to pursue nPM1100 further.  I would suggest you look at the nPM1300, nPM2100 and nPM6001 as well to see which would be best for your application, and then get an EK board to try it out before designing it in.

[Bendik Heiskel]

Hi,

Not sure what happened to this ticket, but I update with an answer(better late than never).

During the battery detection the VBAT pin will be raised to above 2.1V, if the battery is under 2.1V the 1uF capacitor on the VBAT pin will keep the voltage on the VBAT pin long enough for the charging to start.

Without the capacitor the VBAT voltage will drop to 0V after the battery detection and trigger over discharge protection immediately resulting in the charger not starting.

 

If you have any more questions please open a new ticket.

 

Best regards,

Bendik

[DBT]

I just received an email today stating "There is a new Product Change Notice 213 for nPM1300, in which the battery detection functionality has been removed and is no longer required to initiate charging. This functionality has been removed from the nPM1300 Product Specification v1.2.
The improved revision of the nPM1300 fixes erratas from nPM1300 Revision 1 Errata v1.2." so it sounds like this issue might be addressed in nPM1300