Compact 2-Port USB Charger Module

This project designs a two‑port USB charger that operates from a 12 V input and delivers up to 15 W (5 V at 3 A) per port. It uses a buck converter and power‑distribution switches to provide regulated, current‑limited 5 V outputs. The board is designed as a pluggable module but can be modified to include through‑hole pins or flying leads.

Schematic Design

This section explains the selection of key components such as the buck converter and USB power switches and how they interact in the schematic.

• Buck converter – The LM73606 synchronous buck converter steps down the 12 V input to a 5 V rail. A large inductor and banks of input and output capacitors reduce ripple and ensure stable power delivery.
• USB switches – Each port uses a TPS2549 power‑distribution switch. These ICs provide current limiting, port power control and role detection for USB charging.
• Indicator LEDs – LEDs connected to the TPS2549 fault pins provide visual indication of charging status.
• Connectors and sockets – Socket footprints are used for the 12 V input, ground and a DIM control pin. Two USB A connectors provide the outputs.
• Differential pair considerations – The D+ and D– lines from each TPS2549 to the USB connectors form differential pairs. Assign net labels with “_P” and “_N” suffixes and add differential pair directives in the schematic to aid routing.

Layout Strategy

Compact layout is critical in charger designs. The guidelines here discuss board size, layer count, placement and routing for the dual‑port charger.

• Board size and layers – The layout is compact: 31.7 mm × 18.6 mm. It can be implemented on a 2‑layer board, though a 4‑layer stack with internal power and ground planes offers better impedance control and EMI shielding.
• Component placement – Place large components like the USB connectors and buck converter in the PCB editor, then define the board outline around them. Use both sides of the board for placement to save space.
• Routing – Route the two differential pairs from the TPS2549 to the USB connectors using the interactive differential pair router. Use wide traces and larger vias for the power and ground nets.
• Power polygons – Create copper polygons for the 5 V and ground nets. This reduces impedance and simplifies routing. Place silkscreen markings on the top and bottom layers to label the input pins and component reference designators.

Using The Charger

Follow these steps to supply power to the charger, connect devices and monitor their charging status.

• Input power – Connect a 12 V supply to the input pads. Ensure the power source can provide at least 6 A if both ports are used at full load.
• Charging devices – Plug devices into the USB A ports. Each port can supply up to 3 A. The TPS2549 monitors current and will limit or disable a port if an over‑current condition occurs.
• Control and indicators – Use the DIM pin to enable or disable both ports simultaneously. The LEDs indicate power and fault status for each port.

This design illustrates a reliable USB charger that delivers high current while protecting connected devices. The design can be adapted for different input voltages or additional ports by selecting appropriate buck converters and power‑switch ICs.

In addition to charging phones and tablets, the module can power single‑board computers or development kits that require a stable 5 V supply. The TPS2549 supports BC1.2 and DCP protocols, enabling fast‑charging negotiation with compatible devices. If you plan to deliver power over USB‑C connectors instead of USB A, select switches with USB‑C port control capabilities and update the layout accordingly. Always perform thermal analysis to ensure that the buck converter and switches remain within their safe operating area under full load.