NPM1304

[c2scott]

Is there any characterization for the nPM1304 (or any in the series) with a charging input voltage in the 3.5-4.0 range? I have a ~4V power source, but depending on load it may dip below 4V.

(As a side note to Nordic: nPM1304 is not yet selectable in DevZone for posting this question).

[mathiaso]

Hi, Scott.

Have you had a look at the electrical characteristics in the nPM1304's preliminary datasheet?

Best regards,
Mathias

[c2scott]

I've tried.  Under the link provided I see no insight.  Under https://docs.nordicsemi.com/bundle/ps_npm1300/page/vbusin.html#ariaid-title7  I See VBUSmin is 3.6v, but not clear what happens under 4v.  I see chart showing VBusIn vs VSYS but only characterizes to VBUS to 4V.  Maybe I'm missing something or the only choice is to set up a board and experiment.  

[mathiaso]

As you say, VBUS_MIN is 3.6V, so it is possible to charge a battery in the VBUS voltage region of 3.6-4.0V, as long as VBUS - VBAT > 160mV (VBUSVALIDF). If this difference goes below 160 mV, it will only resume when it goes > ~200mV (VBUSVALIDR). 

But beware that if VBUS dips below 3.6V, the nPM1304 will switch back to VBAT as the power source until VBUS recovers to > 3.9V. Additionally, in a depleted battery scenario, you would not be able to boot up with VBUS < 3.9 V, and you would get brownouts if VBUS drops below 3.8V.

We've not done any characterisation of the charging in the region where VBUS is between 3.6 and 4.0V, so I'm afraid you'll have to perform your own testing here.

[c2scott]

Thank you, so noted.  If characterization is performed I'd appreciate an update, but understand this is not the intended use case.