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LLS3 - I2C Charger/PMIC (2x Voltage Out) + RTC

Tiny I2C Programmable LiPo Battery Charger/Monitor, Buck, Buck-Boost, RTC and I2C level shifter

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This is an I2C programmable module that aims to cover the basic needs of battery powered microcontroller projects.

It has two programmable voltage outputs that can be adjusted/enabled/disabled according to your application requirements.

To enable I2C communication between the two voltage domains, the board also has a level shifter integrated onto it.

The charger has extensive battery protection and monitoring features so you can deploy your device in a safe manner.

With the supercapacitor backed RTC it is ideal for solar powered sensor nodes that might not be able to keep a charged battery year-round but still need accurate timestamps.

Why I made it

When building microcontroller projects I often found myself cobbling together an RTC, a charger and some sort of regulator often in the form of breakout boards.

Most of the time you end up with a working, albeit not-so-pretty but colorful salad of wires.

While browsing charging ICs from various manufacturers i stumbled upon the ADP5360. It is marketed as an "Advanced Battery Management PMIC" which it totally is. There is none quite like it, but what intimidated me was that it is only available as an 0.4mm pitch WLCSP (Wafer-level Chip Scale Package).

Last year I dumped a bunch of money on this project taking advantage of the assembly service many PCB manufacturers offer. I would consider it a great learning experience but I wasn't quite satisfied with the result.

So this year I decided to have a new take on the old project and cram what I consider the most essential components onto a small PCB module with castellated edges so I could use it for prototyping as well as as solder-on module for "finished" projects.

As far as I know this is the first module using the ADP5360. Combined with the extremely accurate MAX31343 RTC and a level shifter it is a lot of premium components on a very small module that can enable anyone to make low-power battery powered devices.

Features Overview

What follows is a list of this boards features that should give you a broad idea of the module's capabilities. If you want to know more about the details consider reading the linked datasheets.

Buck/Buck-Boost

  • Buck: 0.6-3.75V (1.8V default) current limit: 100-400mA
  • Buck-Boost: 1.8-5.5V (3.3V default) current limit: 100-800mA
  • 1.1A max drain current from battery

Li-Po Charger

  • Battery protection
  • NTC temperature sensor (optional)
  • Compliant with JEITA charge temperature specification
  • Battery fuel gauge (battery capacity adjustment with aging/temperature)

RTC

  • High accuracy (±5ppm)
  • Two time-of-day alarms
  • Supercapacitor backup

I2C level shifter

  • Converts I2C clock and data lines between configured levels
  • Integrated 10 kOhm pull-up resistors
  • Enable/Disable pin (power saving)

Other features

  • Small footprint: 2x2 cm (0.8x0.8 in)
  • Castellated edges -> breadboard and PCB friendly
  • "Shipment mode"

  • Yield Rate Update

    Leonard Pollak08/28/2021 at 07:36 0 comments

    After my initial two attempts at soldering these boards I was confident I would end up with a higher yield rate >50%.

    Apparently I was wrong.

    After soldering 11 boards I ended up with 2.5/11 working ones which is a yield rate of ~22%.
    The .5 had problems with the level shifter but is otherwise OK.

    Lessons learned:

    • soldering 0.4mm pitch WLCSP is hard
    • proper stencil alignment and paste application is mandatory
    • proper soldering equipment is a must (hot plate + hot air is too inconsistent)
    • blaming the equipment for your mistakes is always possible

    In short this means that these boards will not be available in my tindie store for a little while. I will have to fix the aperture for the stencil in some places and get a proper hot air oven (probably a modded toaster).

    I am still happy the layout of the board was correct on the first try and, as usual, I learned a lot in the process of breaking things. I have also added a picture of my testing jig for your enjoyment.

  • Hackaday Prize 2021

    Leonard Pollak08/21/2021 at 14:54 0 comments

    Today I saw on the hackaday blog that there is a running contest for which this project might be eligible. I've updated the projects details with a "Why I made it" section and added two pictures with application examples for the module.

  • Hardware Update

    Leonard Pollak08/19/2021 at 18:52 0 comments

    Today the PCBs arrived! Yay!

    I soldered two of them which was kind of tricky since the components are really, really small.

    The first one I soldered was a fail. I could see solder bridges under the ADP5360

    chip. The second one (the one with the pin headers) turned out nicely and both I2C devices

    showed up.

    Except for a few missing capacitors that went flying somewhere and the one board with shorts (which I

    kind of expected since it was a first for me) I am quite happy with the results up until now.

    I have enough of the expensive components to solder 9 more which I will hopefully be able to do

    this weekend.

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