Li-Ion / LiPo charger 4.2 V, 500 mA
Linear single-cell Li-Ion / LiPo charger from USB 5 V, 4.2 V charge voltage and 500 mA charge current, with the battery on a Molex PicoBlade connector. An open-drain status output tells the MCU when the battery is charging. A switched divider gives half the battery voltage to the MCU ADC and draws no current when not measuring.
Key specifications
- Input 3.75–6 V (USB 5 V)
- Charge voltage 4.2 V, charge current 500 mA
- Charge status: open drain, low = charging
- Battery voltage / 2 for the ADC while the divider is enabled
Design notes
- Open point: the divider switch may not turn on fully at a full battery with 3.3 V logic, so the ADC reading can be low. To be measured on the first boards; if needed, the switch moves to the low side of the divider.
Seen in real hardware
This block is not available yet. It is released once its checks are complete. Planned price: €29.
Planned package contents
KiCad 10 design block
Schematic and PCB layout fragment; symbols and footprints embedded
BOM (CSV)
Manufacturer part numbers and LCSC codes
Schematic PDF + README
Interface, specs, population options and design notes
3D models
STEP models of the special parts; standard parts use KiCad’s 3D library
template.yaml
Machine-readable interface and limits
PCB Composer
Get blocks like this one composed and routed into one board for your device, without opening KiCad. Quote within 24 h.
About PCB ComposerDevelopment status
| Block ID | 0125 |
|---|---|
| Block name | 0125-liion-charger-4v2-500ma |
| Version | 1.1 |
| Status | DRC clean – Schematic and layout pass the KiCad rule checks; not yet verified on hardware. |
| Open review items | 1 (0 blocking) |
| PCB layout | Rule-checked layout fragment |
| Format | KiCad 10 design block (schematic + PCB) |
| Last change | 2026-11-03 |
Interface
Hierarchical labels the block exposes to the rest of your design.
| Net | Direction | Description |
|---|---|---|
| VBUS | Power in | USB 5 V charger input |
| +BATT | Power out | Battery + (battery connector), charger output |
| AI_BATTERY_FBK | Output | Battery voltage / 2 for the MCU ADC while DO_SUPPLY_EN is high |
| DI_CHARGE_STATE | Output | Charge status, open drain with pull-up to LOGIC_SUP, low = charging |
| DO_SUPPLY_EN | Input | High = battery divider on (for a measurement) |
| LOGIC_SUP | Power in | Pull-up supply for DI_CHARGE_STATE; connect to the MCU logic supply |
FAQ
Which KiCad version do I need?
KiCad 10. The files are saved in the KiCad 10 format and are meant to be placed with KiCad’s Design Blocks feature (schematic block, then “Apply Design Block Layout” on the PCB).
Do I need the Circuit Issues part library?
No. Symbols are embedded in the schematic and footprints in the PCB, so the block opens on its own. Parts carry manufacturer part numbers and LCSC codes.
Is the layout production-ready?
The layout fragment passes the KiCad design rule check. Route it into your board and run DRC with your own fab rules.
Can I use the template in a commercial product?
The licence terms are published together with the first release.
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Designed