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
| Pin(s) | Signal | Purpose | Speed |
|---|---|---|---|
| A1, A12, B1, B12 | GND | Ground reference | - |
| A4, A9, B4, B9 | VBUS | Power delivery (5V-20V) | - |
| A5 | CC1 | Configuration Channel 1 | - |
| B5 | CC2 | Configuration Channel 2 | - |
| A6, A7, B6, B7 | D+, D- | USB 2.0 data | 480 Mbps |
| A2, A3 | TX1+, TX1- | SuperSpeed TX Lane 1 | 5-10 Gbps |
| A10, A11 | RX2-, RX2+ | SuperSpeed RX Lane 2 | 5-10 Gbps |
| B2, B3 | TX2-, TX2+ | SuperSpeed TX Lane 2 | 5-10 Gbps |
| B10, B11 | RX1-, RX1+ | SuperSpeed RX Lane 1 | 5-10 Gbps |
| A8 | SBU1 | Sideband Use 1 | Alternate modes |
| B8 | SBU2 | Sideband Use 2 | Alternate modes |
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
| Pin | Signal | Purpose |
|---|---|---|
| 1, 6 | GND | Ground reference |
| 2, 5 | VBUS | Power delivery (5V-20V) |
| 3 | CC1 | Configuration Channel 1 (orientation & PD) |
| 4 | CC2 | Configuration Channel 2 (orientation & PD) |
This project uses a 6-pin connector (JLCPCB C2927029) - see J1 USB-C Connector documentation.
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 → CH224D detects cable on CC1
- CC2 inactive
Orientation 2 (flipped):
- CC2 active → CH224D detects cable on CC2
- CC1 inactive
2. Current Advertisement (Non-PD)
For standard USB Type-C (without PD negotiation), CC pins advertise available current:
| Rp (Pull-up resistor on source) | Advertised Current |
|---|---|
| 56kΩ | Default USB (500-900mA) |
| 22kΩ | 1.5A @ 5V |
| 10kΩ | 3A @ 5V |
3. Power Delivery Negotiation
With USB-PD (like CH224D), CC pins carry digital communication:
Negotiation Sequence:
1. Initial Connection (0-100ms):
┌─────────┐ ┌─────────┐
│ Source │ ─── CC line ────→ │ Sink │
│ (PD │ │ (CH224D)│
│ 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:
- Distribute current: Each pin carries a portion of total current
- Reduce resistance: Parallel pins = lower resistance
- 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 → CH224D pin 2
│ (via wide trace or copper pour)
Pin 5 (VBUS) ──┘
Pin 3 (CC1) ────→ CH224D pin 10 (separate)
Pin 4 (CC2) ────→ CH224D pin 11 (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
| Benefit | Single Pin | Both Pins Connected |
|---|---|---|
| Resistance | R | R/2 (half) ✅ |
| Current per pin | 3A | 1.5A (distributed) ✅ |
| Power dissipation | I²R | I²R/4 (quarter) ✅ |
| Voltage drop | High | Low ✅ |
| Heating | High | Low ✅ |
| Reliability | Single point of failure | Redundancy ✅ |
| EMI/Noise | Higher | Lower ✅ |
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:
- Use wide traces (≥1mm) or copper pours for VBUS
- Use multiple vias to connect GND pins to ground plane
- Keep traces short and direct
- 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 this project, the CH224D connects 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
| Feature | 24-Pin Connector | 6-Pin Connector | Winner |
|---|---|---|---|
| Cost | Higher ($0.50-1.00) | Lower ($0.20-0.30) | ✅ 6-pin |
| PCB Space | Larger footprint | Smaller footprint | ✅ 6-pin |
| Complexity | More routing | Simpler routing | ✅ 6-pin |
| Data Transfer | ✅ Yes (USB 2.0/3.x) | ❌ No | 24-pin |
| Power Delivery | ✅ Yes (up to 5A) | ✅ Yes (up to 3A) | Both |
| Stock Availability | Good | Very good | ✅ 6-pin |
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 CH224D 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 USB-C Connector Component Page - Full specifications and footprint
- CH224D USB-PD Controller - PD negotiation IC
- Diagram1: USB-PD Section - Complete circuit diagram
- Open-Drain PG Pin - Understanding the Power Good indicator