Considering the limited space, large batteries cannot be used, so I decided to use the Lir1452 coin-type lithium battery. This battery is 85mAh, which makes it unsuitable for more common and mature battery charging and management solutions. Fortunately, there are solutions specifically designed for small-capacity batteries, and today I’ve drafted the initial circuit.
I’m currently considering using the MCP73831 as the charging IC because it allows setting the charging current between 10–40mA, which is relatively safe, battery-friendly, and suitable for my current cell. In addition to the charging section, the Power Part also needs to handle path control, battery protection, and DC-DC boost functions. As a result, the space that initially seemed sufficient is now starting to feel a bit cramped.
Additionally, since I don’t have prior experience with the overall functionality, I’ve added several test points to the circuit to ensure easier debugging during the initial stages. These test points will help inspect various sections and troubleshoot potential issues more conveniently.
Based on reference materials from more mature solutions and my understanding of the currently selected ICs, the circuit schematic is:
Since this circuit requires manual soldering, large ground fills have been avoided to ensure ease of soldering. Additionally, all ICs use larger package sizes where possible, and the pads are designed for hand-soldering, which should help make the soldering process more convenient.
Of course, the overall layout and placement of the ICs may not look very tidy at the moment, but my priority is to first verify the functionality of the circuit. Once the functionality is confirmed, I will revisit and refine the IC placement and routing to improve the overall organization.
The soldering and testing will be completed next week.