Building a USB Power Delivery Trigger HAT

Overview

This tutorial walks through a USB Power Delivery (USB PD) trigger HAT for Raspberry Pi projects. The board uses a fixed-voltage PD trigger controller such as the CH224K, FP28XX, or PD2001 family to request 5 V, 9 V, 12 V, 15 V, or 20 V from a USB-C PD charger, then routes the negotiated output to screw terminals for external loads.

The design is useful when a Raspberry Pi project needs a higher-voltage auxiliary rail for motors, LED strips, small actuators, or bench testing while keeping the control electronics on the Pi header isolated from high-current output paths.

Safety Notes

USB PD can deliver far more power than a normal 5 V USB port. Treat the output terminal as a power rail, not a GPIO signal.

• Verify the requested voltage before connecting a load.
• Size traces, connectors, and terminal blocks for the maximum current you expect.
• Add a fuse or resettable polyfuse for field-use boards.
• Keep the negotiated VBUS output away from Raspberry Pi 3.3 V GPIO pins.
• Use a USB-C PD charger and cable rated for the voltage/current you plan to draw.

Bill of Materials

Ref	Part	Suggested value	Notes
J1	USB-C receptacle	16-pin or 24-pin	Needs VBUS, GND, CC1, CC2 routed
U1	PD trigger controller	CH224K / FP28XX / PD2001	Pick a controller with fixed-voltage configuration pins
SW1	DIP switch or solder jumpers	3-bit select	Chooses 5 V, 9 V, 12 V, 15 V, or 20 V mode
C1	Bulk capacitor	10 uF to 47 uF	Place near U1/VBUS input
C2	Decoupling capacitor	100 nF	Place close to U1 supply pins
LED1	Status LED	Green	Shows power-good or negotiated output
R1	LED resistor	1 kΩ	Adjust for LED brightness
J2	Terminal block	2-4 positions	Output rail and ground

How the Circuit Works

A fixed-voltage PD trigger controller behaves like a USB-C sink device. It reads the charger capabilities through CC1/CC2, advertises the requested profile, and then allows the charger to raise VBUS from the default 5 V to the selected voltage.

The Raspberry Pi header is included only to provide the HAT outline and optional monitoring points. The high-current negotiated rail should not be fed directly into Raspberry Pi GPIO. If you want the Pi to sense power-good, use a divider or optocoupler so the GPIO never sees more than 3.3 V.

Step 1: Start with the HAT board

import { RaspberryPiHatBoard } from "@tscircuit/common"

export default () => (
  <RaspberryPiHatBoard name="HAT1">
    {/* USB PD trigger circuit goes here */}
  </RaspberryPiHatBoard>
)

Step 2: Add the USB-C input and PD controller

Route CC1 and CC2 as short, clean signal traces. Do not add random pull-up or pull-down values unless the controller datasheet calls for them; most trigger ICs integrate the USB-C sink behavior internally.

Step 3: Add filtering capacitors

Use a bulk capacitor for load transients and a 100 nF capacitor close to the controller. For long output leads or motor loads, add more output capacitance at the terminal block.

Step 4: Add voltage selection

Most fixed PD trigger ICs select the target voltage through resistor straps, solder jumpers, or logic pins. In this tutorial, a small DIP switch pulls configuration pins to ground.

Target voltage	Typical use
5 V	Logic, USB accessories, low-power boards
9 V	LED strips, small analog circuits
12 V	Fans, relays, motors, lab loads
15 V	Medium-power prototypes
20 V	High-power loads; verify every downstream rating

Always check the exact configuration truth table in your controller datasheet. CH224K, FP28XX, and PD2001-style parts do not all use the same pin names or resistor values.

Step 5: Add terminal output and status LED

import { RaspberryPiHatBoard } from "@tscircuit/common"

export default () => (
<RaspberryPiHatBoard name="HAT1">
  <chip
    name="U1"
    footprint="sop16"
    pinLabels={{ pin1: ["VIN"], pin2: ["GND"], pin8: ["PG"] }}
    pcbX={-4}
    pcbY={6}
  />
  <resistor name="R1" resistance="1k" footprint="0603" pcbX={8} pcbY={4} />
  <led name="LED1" color="green" footprint="0603" pcbX={14} pcbY={4} />
  <chip
    name="J2"
    footprint="pinrow4"
    manufacturerPartNumber="Output terminal block"
    pinLabels={{ pin1: ["VOUT+"], pin2: ["VOUT+"], pin3: ["GND"], pin4: ["GND"] }}
    pcbX={20}
    pcbY={-8}
  />
  <trace from=".U1 .PG" to=".R1 > .pin1" />
  <trace from=".R1 > .pin2" to=".LED1 > .anode" />
  <trace from=".LED1 > .cathode" to=".U1 .GND" />
  <trace from=".U1 .VIN" to=".J2 .VOUT+" />
  <trace from=".U1 .GND" to=".J2 .GND" />
</RaspberryPiHatBoard>
)

The terminal block duplicates VOUT and GND pins so heavier wires can be installed more securely. For a production board, add a series fuse and test pads for VBUS and ground.

PCB Layout Guidance

• Put the USB-C connector on the board edge with enough copper clearance around the shell.
• Keep VBUS traces wide. For 2-3 A output, use pours or multiple traces instead of a thin signal trace.
• Place C1/C2 close to the PD controller input pins.
• Keep CC traces away from switching nodes and high-current output copper.
• Use a ground pour on both layers if possible.
• Put the voltage-selection switch where it is accessible but unlikely to be changed accidentally.
• Label the terminal block clearly: VOUT+, GND, and selected voltage.

import { RaspberryPiHatBoard } from "@tscircuit/common"

export default () => (
<RaspberryPiHatBoard name="HAT1">
  <chip name="J1" footprint="usb_c" pinLabels={{ pin1: ["VBUS"], pin2: ["GND"], pin3: ["CC1"], pin4: ["CC2"] }} pcbX={-18} pcbY={8} />
  <chip name="U1" footprint="sop16" pinLabels={{ pin1: ["VIN"], pin2: ["GND"], pin3: ["CC1"], pin4: ["CC2"], pin8: ["PG"] }} pcbX={-4} pcbY={6} />
  <capacitor name="C1" capacitance="10uF" footprint="0805" pcbX={-10} pcbY={0} />
  <capacitor name="C2" capacitance="100nF" footprint="0603" pcbX={-2} pcbY={0} />
  <resistor name="R1" resistance="1k" footprint="0603" pcbX={8} pcbY={4} />
  <led name="LED1" color="green" footprint="0603" pcbX={14} pcbY={4} />
  <chip name="J2" footprint="pinrow4" pinLabels={{ pin1: ["VOUT+"], pin2: ["VOUT+"], pin3: ["GND"], pin4: ["GND"] }} pcbX={20} pcbY={-8} />
  <trace from=".J1 .VBUS" to=".U1 .VIN" />
  <trace from=".J1 .GND" to=".U1 .GND" />
  <trace from=".J1 .CC1" to=".U1 .CC1" />
  <trace from=".J1 .CC2" to=".U1 .CC2" />
  <trace from=".U1 .VIN" to=".C1 > .pin1" />
  <trace from=".U1 .VIN" to=".C2 > .pin1" />
  <trace from=".C1 > .pin2" to=".U1 .GND" />
  <trace from=".C2 > .pin2" to=".U1 .GND" />
  <trace from=".U1 .PG" to=".R1 > .pin1" />
  <trace from=".R1 > .pin2" to=".LED1 > .anode" />
  <trace from=".LED1 > .cathode" to=".U1 .GND" />
  <trace from=".U1 .VIN" to=".J2 .VOUT+" />
  <trace from=".U1 .GND" to=".J2 .GND" />
</RaspberryPiHatBoard>
)

Bring-up and Testing Procedure

1. Inspect the board before power-up. Confirm there are no solder bridges on the USB-C connector or controller pins.
2. Set the voltage selector to 5 V for the first test.
3. Connect a USB-C PD charger with no load attached.
4. Measure VOUT and GND at the terminal block. It should read close to 5 V.
5. Move the selector to 9 V or 12 V and repeat the measurement only if your load and capacitors are rated for that voltage.
6. Add a current-limited dummy load, then verify the output does not sag or overheat.
7. If a Raspberry Pi is attached, confirm no selected high-voltage rail is connected to GPIO or the Pi 5 V pins unless you intentionally designed a regulated power path.

Optional Raspberry Pi Monitor Script

If you route a divided power-good signal to a GPIO pin, the Pi can log whether the negotiated rail is present. The divider must keep the GPIO input at or below 3.3 V.

from gpiozero import DigitalInputDevice
from time import sleep

POWER_GOOD_GPIO = 17
power_good = DigitalInputDevice(POWER_GOOD_GPIO, pull_up=False)

while True:
    if power_good.value:
        print("USB PD output is present")
    else:
        print("USB PD output is not ready")
    sleep(1)

Troubleshooting

Symptom	Likely cause	Fix
Output stays at 5 V	Charger does not support selected PDO, or config pins are wrong	Try another charger and verify the controller truth table
No output	CC wiring, connector soldering, or controller power issue	Check CC1/CC2 continuity and VBUS at U1
LED never turns on	Power-good pin polarity differs from example	Check the datasheet; some PG pins are open-drain
Voltage drops under load	Cable, charger, trace width, or current limit issue	Use a rated cable/charger and widen output copper
Pi resets when load starts	High-current rail is coupling into Pi supply	Separate load return paths and add bulk capacitance

Next Steps

• Add an eFuse or resettable polyfuse on VOUT.
• Add a buck regulator to generate a clean 5 V rail from 9-20 V.
• Add a voltage divider and ADC input so the Pi can read the negotiated voltage.
• Add mounting holes and silkscreen labels for common PD profiles.
• Generate fabrication files and order prototypes using the Ordering Prototypes guide.