Power management IC for larger battery and higher current

[Scigrapher]

I'm putting together a project that requires a "large" (1500mAh+) rechargable battery, both because of the desire for long times between charges and to enable powering a peripheral that has a significant current draw (PPK2 measurement linked).  The vast majority of the time the display is unpowered, but a few times a day it will do as in the measurement - ~230mA average, 1.32A max, ignoring a 1.5A spike when it first is enabled).  I'm looking for a solution with LiPo battery charging, USB power input (no PD needed), fuel gauging, support for the display's current draw (plus safety buffer), and a low power usage.  I happen to have an nPM1304EK that I've been using for a smaller version that works great, but I don't think it's going to scale up to the full size because of the increased current requirements.  

If I used the nPM1304, I have to figure out a couple of problems:

1. Powering the display - Have a separate buck off the unregulated rail (which I THINK can handle this load?  I can't find whre I saw the max current) for powering the display. I have some components that should work, but if you have recommendations on something with a low IQ and supports ~2A, I'd love to hear it.
2. Battery support - Figure out how to create a battery profile for the large battery.  PowerUp doesn't support anything even remotely close to 1500mAh.  It doesn't really matter to me that it might take a day to charge it.

Alternatively, I can use something else besides the nPM1304.  It seems like my project might be outside the target audience for it.

Any thoughts or recommendations?

  PPK2 recording:  13 Inch display update.ppk2

[mathiaso]

Hi, Patrick.

At a first glance, it seems like the nPM1300 should at least be closer to what you need than the nPM1304.

If you can help me to shortly summarise this, what you need is a PMIC that'll be able to support a 1500mAh battery and to deliver currents up to 1500mA? Or will it need to deliver up to 2000mA?

Some pointers may be given to you by looking at the nPM1300 and nPM1304 product overviews:

• nPM1300 supports charging up to 800 mA and delivers up to 500 mA of adjustable regulated voltage. Power is supplied to external components from two configurable, dual mode 200 mA BUCK regulators, and two dual purpose 50 mA LDO/100 mA load switches. In addition, an unregulated power rail delivers up to 1340 mA when powered from battery, or up to 1.5 A when powered from a USB port configured as DCP.
• nPM1304 supports charging up to 100 mA and delivers adjustable regulated voltage to external components from two configurable, dual mode 200 mA BUCK regulators, and two dual purpose 50 mA LDO/100 mA load switches. An unregulated power rail delivers up to 150 mA (the current consumed by the BUCKs and LDOs included) when powered from battery, or up to 1.5 A when powered from a USB port configured as DCP.

Battery support - Figure out how to create a battery profile for the large battery.  PowerUp doesn't support anything even remotely close to 1500mAh.  It doesn't really matter to me that it might take a day to charge it.

The nPM Fuel Gauge Board supports batteries with capacities ranging from 100 mAh to 3000 mAh, so this shouldn't be a problem with the nPM1300 at least. As described here, the nPM1304 EK includes battery profiling functionality to generate the battery model, and hence doesn't need the nPM Fuel Gauge Board.

Best regards,
Mathias

[Scigrapher]

The nPM1300 definitely seems closer to what I need.  Ideally it would be able to deliver 2A just to give me some safety factor, since the display will likely pull 1.5A at points, but I'd be willing to try it to see.  I haven't done extensive current testing with the display, just collected recordings of some examples.  The PPK2 is pretty convenient!

A 1500mAh battery is more of a minimum to support the current draw (typically they seem to be rated 1C).  It's coincidentally about where I think it needs to be to support ~ 1 year on a charge, which is the project goal.  That depends largely on usage.  With the nRF54l15 I've gotten my current under 200 uA average, so I can't imagine needing more than 3Ah... that would likely mean I messed up the firmware.

What worries me is that you say the unregulated rail only goes up to 1340mA on battery.  My project will almost exclusively be on battery power (unless charging), and that's right at the limit of what my recording says I need.  That said, the peaks above what the rail supports are very short (< 100 microseconds) and intermittent (~20 ms between peaks), so it's possible that I can mitigate the peaks with capacitors.  I don't suppose the PMIC can handle short bursts above the limit like this?

Are there any reference/example/tutorial boards that use an external buck on the unregulated rail?  I'm just getting into this and having examples to study could be really useful.

[mathiaso]

Scigrapher said:

What worries me is that you say the unregulated rail only goes up to 1340mA on battery.  My project will almost exclusively be on battery power (unless charging), and that's right at the limit of what my recording says I need.  That said, the peaks above what the rail supports are very short (< 100 microseconds) and intermittent (~20 ms between peaks), so it's possible that I can mitigate the peaks with capacitors.  I don't suppose the PMIC can handle short bursts above the limit like this?

I'll check this up internally for you.

Scigrapher said:

Are there any reference/example/tutorial boards that use an external buck on the unregulated rail?  I'm just getting into this and having examples to study could be really useful.

Do you mean connecting VSYS (the unregulated output rail) and an external buck in parallel to drive one single device (the display you're talking about in this case)?

And would you, btw, be able to upload the pptx file directly here in the ticket, instead of using the OneDrive link?

[Scigrapher]

No, I mean just connecting the external buck to VSYS and driving a single device from it.  Nothing crazy.  It'd be helpful to see a design that does it and so I'd have something to reference and compare against.  I have no idea if there is a collection of open reference boards out there that people can look at (other than the DKs/EKs).  If you know of anything like that, please let me know.

It didn't let me upload it before, but let me try again.

13 Inch display update.ppk2

[Scigrapher]

It worked!  Here's a quick description:  The initial spike is the inrush current when the display is enabled.  Then there's an initialization phase, uploading the image data to the display, and then clearing and showing the new image on the display.  It's an e-ink display, so it takes a while.

[mathiaso]

Cool to hear!

I got an answer to the internal ticket I created as well.

1340mA is the limit we can support from VSYS. This is limited by the discharge current limit of the battery. It is possible to use bigger bulk caps at the display for filtering of the short pulses. You can add the capacitor and use the PPK2 to characterise the current profile to make sure the current stays below the current limit.

Regarding your request for a recommendation of a discrete buck, I'm afraid it's difficult for us to recommend parts we haven't designed ourselves.

[Scigrapher]

If 1340mA is limited by the discharge current of the battery, does that mean a battery with a higher discharge current will result in a higher supported VSYS current?  The discharge current of the battery I'll be using will be 1500mA+.

My nPM1300EK should be arriving today, so hopefully I can start trying things out soon.  I'll need to do some calculations for the capacitors.  

I understand about the recommendation.  I have a buck EK from TI I'm going to give a go.

[mathiaso]

Scigrapher said:

If 1340mA is limited by the discharge current of the battery, does that mean a battery with a higher discharge current will result in a higher supported VSYS current?  The discharge current of the battery I'll be using will be 1500mA+.

No, might not have been the best formulation there. I'm sorry. By the discharge current limit, we're talking about the current limiter of the nPM1300 itself. The battery current limit has two settings, 280mA and 1460mA (typical). And when adding some margin, we get a maximum current of 1340mA.