USB Type-C Pinout and Power Delivery

Understanding USB Type-C connector pinout and how it enables USB Power Delivery (PD) negotiation.

Full USB Type-C Pinout (24-pin)

A full USB Type-C receptacle has 24 pins arranged symmetrically to support reversible insertion:

USB Type-C Receptacle (24-pin)
Receptacle Front View (looking into connector)

Top Row (A-side):
┌────────────────────────────────────────────────────┐
│ A1   A2   A3   A4   A5   A6   A7   A8   A9  A10  A11  A12 │
│ GND  TX1+ TX1- VBUS CC1  D+   D-  SBU1 VBUS RX2- RX2+ GND │
└────────────────────────────────────────────────────┘

Bottom Row (B-side):
┌────────────────────────────────────────────────────┐
│ B12  B11  B10  B9   B8   B7   B6   B5   B4   B3   B2   B1  │
│ GND  RX1- RX1+ VBUS SBU2 D-   D+  CC2  VBUS TX2- TX2+ GND │
└────────────────────────────────────────────────────┘

Pin Functions

Simplified USB Type-C for Power-Only (6-pin)

For applications requiring only power delivery (no data transfer), a simplified 6-pin connector is sufficient:

USB Type-C 6-Pin Connector (Power-Only)

┌──────────────────┐
│   1    2    3    │  Top Row
│  GND  VBUS  CC1  │
└──────────────────┘
┌──────────────────┐
│  CC2  VBUS  GND  │  Bottom Row
│   4    5    6    │
└──────────────────┘

6-Pin Functions

This project uses a 6-pin connector (JLCPCB C456012) - see J1 substitution options.

Configuration Channel (CC) Pins

The CC pins are critical for USB Power Delivery. They serve multiple purposes:

1. Cable Orientation Detection

USB Type-C is reversible. When you plug in a cable:

• Only one CC pin is active at a time

• The active CC pin identifies cable orientation

• The other CC pin remains inactive

Example:

Orientation 1 (normal):
- CC1 active → the PD sink controller detects cable on CC1
- CC2 inactive

Orientation 2 (flipped):
- CC2 active → the PD sink controller detects cable on CC2
- CC1 inactive

2. Current Advertisement (Non-PD)

For standard USB Type-C (without PD negotiation), CC pins advertise available current:

3. Power Delivery Negotiation

With USB-PD (negotiated by this project's STUSB4500, U1), CC pins carry digital communication:

Negotiation Sequence:

1. Initial Connection (0-100ms):
   ┌─────────┐                    ┌─────────┐
   │ Source  │ ─── CC line ────→  │  Sink   │
   │ (PD     │                    │  (U1)   │
   │ Charger)│                    │         │
   └─────────┘                    └─────────┘
   VBUS = 5V (default)

2. Capability Discovery (100-200ms):
   ┌─────────┐                    ┌─────────┐
   │ Source  │ ←── CC line ────   │  Sink   │
   │         │  "What voltages    │         │
   │         │   do you have?"    │         │
   └─────────┘                    └─────────┘

   Source responds:
   - 5V @ 3A
   - 9V @ 3A
   - 12V @ 3A
   - 15V @ 3A ✅
   - 20V @ 2.25A

3. Voltage Request (200-300ms):
   ┌─────────┐                    ┌─────────┐
   │ Source  │ ←── CC line ────   │  Sink   │
   │         │  "I want 15V/3A"   │         │
   │         │                    │         │
   └─────────┘                    └─────────┘

4. Acceptance (300-500ms):
   ┌─────────┐                    ┌─────────┐
   │ Source  │ ─── CC line ────→  │  Sink   │
   │         │  "OK, switching"   │         │
   │         │                    │         │
   └─────────┘                    └─────────┘

5. Voltage Transition (500-1000ms):
   VBUS transitions: 5V → 15V

6. Power Ready (>1000ms):
   VBUS stable at 15V
   System draws up to 45W (15V × 3A)

VBUS Pins and Current Distribution

Why Multiple VBUS Pins?

USB Type-C has 4 VBUS pins (A4, A9, B4, B9) to:

1. Distribute current: Each pin carries a portion of total current

2. Reduce resistance: Parallel pins = lower resistance

3. Improve reliability: Redundancy in case of poor contact

Current distribution example (3A total):

A4 ──┬─→ ~0.75A
     │
A9 ──┤─→ ~0.75A
     │
B4 ──┤─→ ~0.75A       Total: 3A
     │
B9 ──┴─→ ~0.75A

6-Pin Connector VBUS

In 6-pin connectors, only 2 VBUS pins are present (pins 2, 5):

• Maximum current: 3A (sufficient for most USB-PD applications)

• Current distribution: ~1.5A per pin

This is adequate for our 15V/3A (45W) power supply.

Critical: Always Connect Redundant Pins Together

Why Connect Both VBUS Pins Together?

USB Type-C has redundant power pins by design. For 6-pin connectors, this means:

• 2 VBUS pins (pins 2, 5)

• 2 GND pins (pins 1, 6)

You must ALWAYS connect both pins of each type together. Never connect just one!

✅ Correct Connection Strategy

J1 (USB-C 6P Connector)

Pin 1 (GND)  ──┬─→ System GND
               │   (via wide trace or ground plane)
Pin 6 (GND)  ──┘

Pin 2 (VBUS) ──┬─→ VBUS node → PD sink controller VBUS pin
               │   (via wide trace or copper pour)
Pin 5 (VBUS) ──┘

Pin 3 (CC1)  ────→ PD sink controller CC1 pin (separate)
Pin 4 (CC2)  ────→ PD sink controller CC2 pin (separate)

❌ Wrong: Connecting Only One Pin

❌ WRONG:
Pin 1 (GND)  ──→ System GND
Pin 6 (GND)  ──→ Not connected  ❌

Pin 2 (VBUS) ──→ VBUS node
Pin 5 (VBUS) ──→ Not connected  ❌

Benefits of Connecting Both Pins

Why This Matters: Practical Example

Scenario: 15V @ 3A power delivery

❌ Using Only One GND Pin:

Resistance: 10mΩ (typical pin + trace resistance)
Current: 3A (full current through one pin)
Voltage drop: V = I × R = 3A × 10mΩ = 30mV
Power dissipation: P = I² × R = 9W × 10mΩ = 90mW (heats up!)

✅ Using Both GND Pins:

Resistance: 5mΩ (two pins in parallel)
Current per pin: 1.5A (distributed)
Voltage drop: V = I × R = 3A × 5mΩ = 15mV (half!)
Power dissipation: P = I² × R = 9W × 5mΩ = 45mW (half the heating!)

Result: Connecting both pins gives you:

• 50% less voltage drop

• 50% less heating

• Better reliability with redundancy

PCB Layout Best Practices

Top Copper Layer:

┌────────────────────────────────┐
│  USB-C Connector J1            │
│                                │
│  Pin 1 (GND) ────┐             │
│                  ├──→ Via to GND plane
│  Pin 6 (GND) ────┘             │
│                                │
│  Pin 2 (VBUS) ───┐             │
│                  ├──→ Wide trace to VBUS
│  Pin 5 (VBUS) ───┘             │
└────────────────────────────────┘

Ground Plane (Internal Layer):
████████████████████████████████
█ Solid copper pour             █
█ Multiple vias from pins 1, 6  █
████████████████████████████████

Key points:

1. Use wide traces (≥1mm) or copper pours for VBUS

2. Use multiple vias to connect GND pins to ground plane

3. Keep traces short and direct

4. Use symmetrical routing when possible

USB-C Specification Requirement

The USB Type-C specification requires all redundant power pins to be connected:

• Ensures proper current distribution

• Guarantees reliable operation in both orientations

• Meets thermal and electrical specifications

• Required for USB-IF certification

Bottom line: Always connect both VBUS pins together AND both GND pins together. This is not optional!

CH224D Connection to USB-C Connector

In the original (v1.0) design, the CH224D connected to the 6-pin USB Type-C connector:

J1 (USB-C 6P)          CH224D (QFN-20)

Pin 1 (GND) ──────────→ Pin 0 (GND/EPAD)
Pin 2 (VBUS) ─────────→ Pin 2 (VBUS)
Pin 3 (CC1) ──────────→ Pin 10 (CC1)
Pin 4 (CC2) ──────────→ Pin 11 (CC2)
Pin 5 (VBUS) ─────────→ Pin 2 (VBUS) (paralleled with pin 2)
Pin 6 (GND) ──────────→ Pin 0 (GND/EPAD)

Key points:

• Both VBUS pins (2, 5) connect to CH224D VBUS (pin 2)

• Both GND pins (1, 6) connect to CH224D GND (pin 0/EPAD)

• CC1 and CC2 are separate signals for orientation detection

• CH224D automatically detects which CC pin is active

Advantages of 6-Pin Power-Only Design

For power-only USB-PD applications, 6-pin connectors are the optimal choice.

Common Misconceptions

❌ "You need all 24 pins for USB-PD"

False. USB-PD only requires VBUS, GND, and CC pins. The 6-pin connector is sufficient for up to 60W (20V/3A).

❌ "CC pins carry power"

False. CC pins carry only low-current signals for communication and detection. Power flows through VBUS pins only.

❌ "Both CC pins are always active"

False. Only one CC pin is active at a time, depending on cable orientation. The PD sink controller automatically detects which one.

❌ "More VBUS pins = more power"

Partially true. More VBUS pins allow higher current (24-pin supports 5A, 6-pin supports 3A), but voltage is the same. For 45W (15V/3A), the 6-pin connector is sufficient.

Related Documentation

• J1 substitution options - Full specifications and footprint

• CH224D USB-PD Controller - PD negotiation IC

• Board A: USB-PD Core - Complete circuit diagram

• Open-Drain PG Pin - Understanding the Power Good indicator

References

• USB Type-C Cable and Connector Specification v2.1

• USB Power Delivery Specification v3.1

• AN4879: USB Type-C Power Delivery Using the STM32 MCU