Power Supply Card

The Power Supply Card is a Tool Card from HW Media Lab LLC that fits a programmable bench power supply into a Framework Expansion Card form factor¹. It is designed to work with the DockFrame modular USB-C hub or plugged directly into any USB-C host, sourcing power entirely from USB-C Power Delivery¹².

In Development

The Power Supply Card is in pre-production as of 2026. A Crowd Supply campaign is planned. All hardware and software will be open-sourced after the campaign closes¹³.

Design

The card uses a USB-C PD front-end followed by a programmable buck-boost converter¹:

• PD sink: STUSB4500QTR, configured to request the highest available contract (up to 20 V)
• Load switch: STL6P3LLH6 P-FET (soft-start, hot-plug, hardware kill)
• System rails: AP64060WU-7 (+5 V), SY8089A1AAC (+3V3)
• Output stage: TPS55289RYQR (30 V I²C-programmable buck-boost)
• MCU: ESP32-S3R8 with WiFi and BLE

The buck-boost topology allows output voltages both below and above the negotiated PD rail (e.g., 12 V output from a 9 V PD contract)¹.

Block Diagram

USB-C PD VBUS (5/9/15/20 V)
  → STUSB4500QTR (PD negotiator)
    → INA180A2 (input current telemetry)
      → STL6P3LLH6 (P-FET load switch)
        ├→ AP64060WU-7 → +5 V → SY8089A1AAC → +3V3
        └→ TPS55289RYQR → programmable output (0.8–22 V)
                             → banana jacks

All rails are managed and monitored by the ESP32-S3 over I²C, with input current sense from the INA180 closing the telemetry loop¹.

Software

Same approach as the Multimeter Card: browser-based app over Web Serial API, no drivers or accounts¹. Protocol is plain text at 115200 baud over USB CDC (SET:V 5.0, SET:I 0.5, OUTPUT ON, READ). A mobile app over BLE is planned¹.

Thermal

The TPS55289 PowerPAD uses three 0.5/0.3 mm thermal vias and ~107 GND vias across the buck-boost stage, achieving ~55 °C/W junction-to-ambient (~37 °C above ambient at full load)¹. SW1/SW2 pads are deliberately un-stitched to avoid noise broadcast¹.

Specifications

Specification	Details
MCU	ESP32-S3R81
PD sink	STUSB4500QTR (up to 20 V)1
Output stage	TPS55289RYQR (I²C buck-boost)1
Output voltage	0.8–22 V programmable1
Input current sense	INA180A21
Wireless	WiFi + BLE (ESP32-S3)1
Host software	Web Serial API (browser-based)1
Connectors	Banana jacks1
License	Open source (CERN-OHL-S hardware, MIT firmware)3
Source	HW-Lab-Hardware-Design-Agency (GitHub)3

Related Projects

Project	Description
DockFrame	HW Media Lab's modular USB-C hub hosting this card
Multimeter Card	Isolated multimeter in the same Tool Card format
Breadboard Card	XIAO-based development card in the same Tool Card format

Footnotes

1. Building a Power Supply in a Framework Expansion Card — HW Lab Blog ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹ ↩¹² ↩¹³ ↩¹⁴ ↩¹⁵ ↩¹⁶ ↩¹⁷ ↩¹⁸

2. DockFrame — HW Media Lab LLC ↩

3. HW-Lab-Hardware-Design-Agency — GitHub ↩ ↩² ↩³