CH224D USB PD Sink Controller
Understanding the CH224D USB Power Delivery sink controller and how it negotiates voltage with PD adapters.
What is CH224D?
CH224D is a USB PD sink controller - a specialized IC that:
- Communicates with USB-C PD (Power Delivery) adapters
- Requests specific voltages (5V, 9V, 12V, 15V, or 20V)
- Negotiates power up to 100W (with E-Mark simulation)
- Handles all PD protocol communication automatically
Key advantage: You don't need a microcontroller - just set a resistor value and the IC does everything!
How USB Power Delivery Works
Traditional USB Power (Without PD)
USB-A Port → Fixed 5V @ 0.5A-3A (max 15W)
Problem: Limited to 5V, insufficient for high-power devices.
USB Power Delivery (With PD)
USB-C PD Adapter ← Negotiation via CC pins → Device (CH224D)
"I need 15V @ 3A"
"OK, switching to 15V"
VBUS: 5V → 15V (voltage changes on same wire!)
Result: Up to 100W power delivery (20V @ 5A)
Critical Concept: VBUS is Both Input and Output
This is the most important thing to understand:
┌─────────────┐ VBUS ┌─────────────┐
│ USB-C │ ────────────────────→ │ CH224D │
│ PD Adapter │ 5V (initial) │ (pin 2) │
│ │ │ │
│ │ ← CC negotiation → │ │
│ │ │ │
│ │ 15V (after PD) │ │
│ │ ────────────────────→ │ │
└─────────────┘ VBUS └─────────────┘
CH224D does NOT have a separate output pin!
- Pin 2 (VBUS) is the ONLY power pin
- Initially: VBUS = 5V (default USB voltage)
- After negotiation: VBUS = 15V (or requested voltage)
- Your circuit connects directly to VBUS
This is fundamentally different from DC-DC converters which have separate input and output pins!
CH224D Pin Functions
Power Pins
| Pin | Name | Type | Function |
|---|---|---|---|
| 2 | VBUS | Power I/O | Main power pin - both input (5V) and output (negotiated voltage) |
| 7 | VDD | Power out | Internal 4.7V LDO output (needs 1µF decoupling cap) |
| 0 | GND (EPAD) | Ground | Thermal pad - connect to ground plane |
Communication Pins (PD Protocol)
| Pin | Name | Type | Function |
|---|---|---|---|
| 11 | CC1 | I/O | Configuration Channel 1 - PD communication |
| 10 | CC2 | I/O | Configuration Channel 2 - PD communication |
| 8 | DP (UDP) | I/O | USB D+ data line (not used in PD-only mode) |
| 9 | DM (UDM) | I/O | USB D- data line (not used in PD-only mode) |
For PD-only applications: Short DP (pin 8) to DM (pin 9) to disable BC1.2 and other USB data protocols.
Configuration Pins
| Pin | Name | Type | Function |
|---|---|---|---|
| 1 | DRV | Analog out | Drives configuration resistor (weak output) |
| 19 | CFG1 | Analog in | Voltage selection input (resistor mode) |
| 13 | CFG2 | Digital in | Voltage selection (level mode, built-in pull-down) |
| 12 | CFG3 | Digital in | Voltage selection (level mode, built-in pull-down) |
How DRV Pin Works (Voltage Selection Magic!)
DRV (pin 1) is a weak voltage output (~4.7V) used to determine which PD voltage you want.
The clever voltage selection circuit:
DRV (pin 1) ──┬── CFG1 (pin 19) ← Connect DRV to CFG1
│
Rset (e.g., 56kΩ)
│
GND
How it determines voltage:
- DRV outputs ~4.7V (weak current, can't power external circuits)
- Rset creates voltage divider between DRV and GND
- Specific voltage appears at CFG1 (depends on Rset value)
- CH224D's internal ADC reads CFG1 voltage
- Based on CFG1 voltage → requests specific PD voltage
Example with our 56kΩ resistor:
DRV (4.7V) ─┬─ CFG1
│
56kΩ ← Creates specific voltage at CFG1
│
GND
CH224D reads CFG1 voltage → "Ah, user wants 15V!" → Requests 15V from PD adapter
Different resistors → Different voltages:
Rset = 6.8kΩ → CFG1 = X volts → Request 9V
Rset = 24kΩ → CFG1 = Y volts → Request 12V
Rset = 56kΩ → CFG1 = Z volts → Request 15V ✅ (our design)
Rset = NC → CFG1 = ~4.7V → Request 20V
Why "weak" output?
- Can drive high-impedance loads (kΩ resistors) ✅
- Cannot drive LEDs, motors, or power circuits ❌
- Just for voltage sensing - perfect for this use!
Simple and elegant: No microcontroller needed - just one resistor tells CH224D what voltage you want!
Power Switching Pins (Internal vs External MOSFET)
CH224D has a built-in MOSFET (rated up to 5A) to switch VBUS power on/off.
| Pin | Name | Function | Our Connection |
|---|---|---|---|
| 5 | GATE | Drives MOSFET gate (internal or external) | NC (not connected - using internal) |
| 6 | NMOS# | Selects internal (LOW) or external (HIGH) MOSFET | GND (use internal MOSFET) |
How It Works:
For ≤5A applications (like ours at 3A):
- Pin 6 (NMOS#) → GND = Use internal MOSFET
- Pin 5 (GATE) → NC (not connected)
- CH224D's internal 5A MOSFET handles the switching
- Simple and works great! ✅
For >5A applications (e.g., 100W chargers):
- Pin 6 (NMOS#) → Configured for external mode
- Pin 5 (GATE) → Connected to external MOSFET gate
- External high-current MOSFET handles the power
- CH224D controls the external MOSFET via GATE pin
Why external MOSFET? When you need more than 5A, you need a more powerful MOSFET that can handle the high current without overheating.
Current Sensing Pins (Optional Feature)
| Pin | Name | Function | Our Connection |
|---|---|---|---|
| 14 | ISP | Current sense positive | Shorted to pin 15 → GND |
| 15 | ISN | Current sense negative | Shorted to pin 14 → GND |
What they do:
- Can monitor current flowing through the power path
- Useful for overcurrent protection or current measurement
- Requires external sense resistor
Why we don't use them:
- CH224D provides built-in overcurrent protection
- Our design doesn't need current monitoring
- Simplifies the circuit
Connection: Short pins 14 and 15 together, then connect to GND.
VDD Pin - Internal Regulator Output
Pin 7 (VDD) is the output of CH224D's internal 4.7V LDO regulator.
Critical requirement: VDD MUST have a 1µF decoupling capacitor to GND!
VDD (pin 7) → C30 (1µF ceramic) → GND
Why C30 is critical:
- ⚡ Regulator stability - LDO requires output cap to remain stable
- 🔇 Noise filtering - Filters high-frequency noise from internal circuits
- ⚡ Transient response - Provides instant current during load changes
- ✨ Clean power - Ensures accurate PD negotiation and voltage selection
Without C30, the CH224D will not work correctly! The internal regulator could oscillate, causing PD negotiation to fail.
Note: VDD powers only the IC's internal circuits (analog/digital logic). Your external circuits connect to VBUS (pin 2), not VDD.
Unused Pins
| Pins | Status |
|---|---|
| 3, 4, 16-18, 20 | NC (Not Connected) - leave floating |
| 18 | NC - No separate output pin! VBUS (pin 2) is both input and output |
Voltage Selection Methods
CH224D supports two configuration methods:
Method 1: Resistor Configuration (Used in This Project)
Simple and static - set once with a resistor value.
Circuit:
DRV (pin 1) ──┬── CFG1 (pin 19)
│
Rset
│
GND
Voltage Selection:
┌──────────┬──────────────────┐
│ Rset │ Requested Voltage│
├──────────┼──────────────────┤
│ 6.8 kΩ │ 9V │
│ 24 kΩ │ 12V │
│ 56 kΩ │ 15V ✅ (This) │
│ NC │ 20V │
└──────────┴──────────────────┘
CFG2 (pin 13) = Open/GND
CFG3 (pin 12) = Open/GND
Advantages:
- ✅ Simple - just one resistor
- ✅ No microcontroller needed
- ✅ Voltage fixed at design time
- ✅ Low cost
Our design uses 56kΩ → 15V
Method 2: Level Configuration
Dynamic - can change voltage with MCU or switches.
Circuit:
CFG1, CFG2, CFG3 connect to MCU GPIO or VDD/GND
Voltage Selection:
┌──────┬──────┬──────┬──────────────────┐
│ CFG1 │ CFG2 │ CFG3 │ Requested Voltage│
├──────┼──────┼──────┼──────────────────┤
│ 1 │ - │ - │ 5V │
│ 0 │ 0 │ 0 │ 9V │
│ 0 │ 0 │ 1 │ 12V │
│ 0 │ 1 │ 1 │ 15V │
│ 0 │ 1 │ 0 │ 20V │
└──────┴──────┴──────┴──────────────────┘
Note: CFG2 and CFG3 have built-in pull-down resistors
Advantages:
- ✅ Dynamic voltage selection
- ✅ Can change voltage during operation
- ✅ Multiple voltage outputs from same board
Disadvantages:
- ❌ Requires MCU or manual switches
- ❌ More complex
- ❌ CFG voltage limits: <5V for CH224D
USB Type-C CC Pin Configuration
The 5.1kΩ Pull-Down Resistors (R12, R13) - CRITICAL!
Without R12 and R13, your circuit will NOT work! These resistors are the "handshake" that starts PD negotiation.
USB-C Connector:
CC1 ───┬──→ CH224D pin 11 (CC1)
│
R12: 5.1kΩ (Rd resistor)
│
GND
CC2 ───┬──→ CH224D pin 10 (CC2)
│
R13: 5.1kΩ (Rd resistor)
│
GND
How USB-C Device Detection Works
Step 1: PD Adapter checks CC pins
PD Adapter sends test signals:
CC1 ──→ Measures resistance to GND
CC2 ──→ Measures resistance to GND
Step 2: Resistance determines device type
Measured Resistance = Device Type:
┌──────────┬─────────────────────────┐
│ 5.1kΩ │ SINK (wants power) ✅ │ ← This is us!
│ 56kΩ │ Audio accessory │
│ Open │ Nothing connected │
│ Other │ Power source or cable │
└──────────┴─────────────────────────┘
Step 3: Cable orientation detection
- USB-C cables can plug in either way (reversible)
- One of CC1 or CC2 will be the "active" pin (lower resistance path)
- Adapter uses the active CC pin for PD communication
- The 5.1kΩ resistor on that pin tells adapter which way cable is oriented
Step 4: Start PD negotiation
- Only if 5.1kΩ detected → Adapter recognizes device as PD sink
- Adapter initiates PD communication via active CC pin
- CH224D requests desired voltage (15V in our case)
- Adapter responds and negotiates power delivery
What Happens WITHOUT R12/R13?
Critical failure scenario:
No 5.1kΩ resistors:
↓
PD adapter sees "open circuit" on CC pins
↓
Adapter thinks: "Nothing connected" or "Wrong device type"
↓
❌ NO PD negotiation happens
↓
❌ VBUS stays at 5V (default USB voltage)
↓
❌ Your circuit gets 5V instead of 15V
↓
❌ DC-DC converters and power supply don't work!
Why Exactly 5.1kΩ?
USB Type-C Specification defines this value:
- Sink devices MUST have Rd = 5.1kΩ (±20%)
- This is a universal standard that all USB-C devices follow
- PD adapters are designed to detect this specific resistance value
- Not arbitrary - it's carefully chosen to distinguish device types
Tolerance:
- ±20% is acceptable (4.08kΩ to 6.12kΩ)
- We use ±1% for reliability (5.05kΩ to 5.15kΩ)
- Part: 0603 5.1kΩ ±1% resistor (JLCPCB C23186)
Component Specifications
| Component | Value | Tolerance | Purpose | JLCPCB Part |
|---|---|---|---|---|
| R12 | 5.1kΩ | ±1% | CC1 pull-down (Rd) | C23186 |
| R13 | 5.1kΩ | ±1% | CC2 pull-down (Rd) | C23186 |
Common Mistakes to Avoid
❌ Mistake 1: Forgetting R12/R13 entirely
- Result: No PD negotiation, stuck at 5V
❌ Mistake 2: Using wrong resistance value
- Result: Adapter misidentifies device type, no PD negotiation
❌ Mistake 3: Only installing one resistor (R12 or R13)
- Result: Cable orientation might not be detected correctly
❌ Mistake 4: Connecting resistors to wrong pins
- Result: CC communication fails
✅ Correct: 5.1kΩ ±1% on BOTH CC1 and CC2 to GND
Summary
R12 and R13 (5.1kΩ pull-downs) are the FIRST thing a PD adapter checks!
Without them:
- ❌ No device identification
- ❌ No PD negotiation
- ❌ No 15V output
- ❌ Circuit doesn't work
With them:
- ✅ Adapter recognizes device as PD sink
- ✅ PD negotiation starts
- ✅ 15V power delivery works
- ✅ Happy modular synth! 🎵
6-Pin vs 24-Pin USB-C Connectors
Full 24-Pin Connector
Pins: VCC, GND (4 each), CC1, CC2, DP, DM, TX/RX lanes, SBU, etc.
Use case: Full USB functionality (data + power)
Cost: Higher
6-Pin Power-Only Connector (Our Choice)
Pins: VBUS (2), GND (2), CC1, CC2
Use case: Power delivery only (no data)
Cost: Lower (~$0.036 vs $0.50+)
Part: C456012 (TYPE-C 6P)
Why 6-pin is sufficient for PD:
- ✅ VBUS pins carry negotiated voltage
- ✅ CC pins handle PD communication
- ✅ GND provides reference
- ✅ No data pins needed for power-only applications
What we lose with 6-pin:
- ❌ No USB data transfer (DP/DM)
- ❌ No alternate modes (DisplayPort, etc.)
- ✅ But we only need power, so perfect!
PD-Only Mode (Why Short DP to DM)
When using 6-pin connector with no DP/DM pins:
Datasheet requirement (Section 5.5):
"If there is no need to use A-port protocols (various protocols realized by DP/DM communication), the DP/DM pin on CH224K/CH224D is required to be disconnected from the DP/DM on the Type-C connector, and the DP pin on CH224 is required to be shorted to the DM on CH224."
CH224D:
Pin 8 (DP) ──┬── Short on PCB
Pin 9 (DM) ──┘
Effect: Disables BC1.2 and other USB data protocols
Result: PD-only operation
Why this matters:
- BC1.2 = Battery Charging specification (uses DP/DM)
- We don't need BC1.2 since we have PD
- Shorting DP to DM tells CH224D to ignore data protocols
- Focuses on PD negotiation only
PD Negotiation Sequence
Step-by-step process when you plug in the USB-C cable:
Step 1: Initial Connection (0-100ms)
┌─────────────┐ ┌─────────────┐
│ USB-C PD │ ──── VBUS ────→ │ CH224D │
│ Adapter │ 5V │ Device │
└─────────────┘ └─────────────┘
VBUS = 5V (default USB voltage)
- Adapter provides 5V default voltage
- CH224D powers up (VDD regulator starts)
- No negotiation yet - just basic USB power
Step 2: Orientation Detection (100-200ms)
CC Pins:
CC1 ─── 5.1kΩ ─── GND } CH224D detects which CC pin
CC2 ─── 5.1kΩ ─── GND } is active (cable orientation)
- USB-C is reversible (can plug in either way)
- Only ONE CC pin is active at a time
- Active CC pin = cable orientation
- 5.1kΩ pull-downs identify device as sink
Step 3: Capability Discovery (200-300ms)
Device: "What voltages do you support?"
Adapter: "I have: 5V/3A, 9V/3A, 12V/3A, 15V/3A, 20V/2.25A"
- CH224D sends Source Capabilities request via CC
- Adapter responds with available power profiles
- This is PD protocol communication (digital)
Step 4: Voltage Request (300-400ms)
CH224D reads CFG1 resistor:
- Rset = 56kΩ detected
- Requests: 15V @ 3A
Device: "I want 15V @ 3A (45W)"
Adapter: "Accepted, switching voltage..."
- CH224D determines requested voltage from Rset
- Sends Request message via CC
- Adapter checks if it can provide that power
Step 5: Voltage Transition (400-1000ms)
VBUS voltage transition:
5V → [ramping] → 15V
Adapter gradually increases VBUS voltage
- Critical: VBUS voltage changes on the same pin!
- Voltage ramps up smoothly (not instant)
- Downstream circuits must handle this transition
- Input capacitors smooth the transition
Step 6: Power Ready (>1000ms)
VBUS = 15V stable
PG pin goes LOW (power good indicator)
System can draw up to 45W (15V × 3A)
- Negotiation complete
- LED1 lights up (PG indicator)
- Main power supply can operate
- DC-DC converters receive 15V input
Design Considerations
Input Filtering
VBUS needs filtering capacitors:
VBUS ──┬─── C1 (10µF) ──→ GND (Bulk filtering)
│
└─── C2 (100nF) ─→ GND (HF decoupling)
Why both capacitors?
- 10µF (bulk): Stores energy during voltage transition (5V→15V)
- 100nF (ceramic): Filters high-frequency noise, placed close to IC
- Together provide stable power during negotiation
VDD Decoupling
Internal 4.7V regulator needs decoupling:
VDD (pin 7) ─── C30 (1µF) ──→ GND
Why needed?
- VDD powers internal circuits
- 1µF cap stabilizes internal regulator
- Prevents oscillation and noise
- Datasheet requires this!
Power Good (PG) Indicator
+5V ──→ R10 (330Ω) ──→ LED1 (Green) ──→ PG (pin 8) ──→ GND
(open-drain)
How it works:
- PG pin is open-drain output
- Normal operation: PG = HIGH (LED off)
- After successful negotiation: PG = LOW (LED on)
- LED lights up when 15V is ready!
Why connect to +5V instead of VBUS?
- VBUS changes from 5V to 15V
- +5V rail is stable (from linear regulator)
- LED brightness stays constant
- No need to worry about voltage changes
PCB Layout Guidelines
Critical traces:
- VBUS: Wide traces (≥1mm) or copper pour - carries up to 3A
- CC pins: Keep traces short, symmetric length, away from noisy signals
- GND: Solid ground plane, thermal pad (pin 0) with multiple vias
- VDD: 1µF cap placed close to pin 7
Component placement:
- C2 (100nF) very close to VBUS pin
- C30 (1µF) very close to VDD pin
- R12, R13 (5.1kΩ CC pull-downs) close to IC
CH224 Family Comparison
There are three variants in the CH224 family:
CH224D (QFN-20) - Used in This Project
- Package: QFN-20 (3×3mm)
- Features: Full featured, VBUS up to 22V, GATE pin for NMOS
- Configuration: Resistor or level mode
- Best for: Advanced designs, higher power
- Cost: Medium
CH224K (ESSOP-10)
- Package: ESSOP-10 (larger)
- Features: Similar to CH224D, has VBUS detection pin
- Configuration: Resistor or level mode
- Best for: Through-hole friendly designs
- Cost: Medium
CH221K (SOT23-6)
- Package: SOT23-6 (tiny!)
- Features: PD protocol only, simplified
- Configuration: Resistor mode only
- Best for: Space-constrained, cost-sensitive
- Cost: Lowest
Why we chose CH224D:
- ✅ Small SMD package (good for JLCPCB assembly)
- ✅ Full PD features
- ✅ Resistor configuration (simple)
- ✅ Good stock availability (2,291 units)
Common Mistakes to Avoid
❌ Mistake 1: Expecting a separate output pin
WRONG thinking:
VBUS (input) → CH224D → VOUT (output)
CORRECT understanding:
VBUS (5V input, 15V output) - same pin!
❌ Mistake 2: Forgetting CC pull-down resistors
WRONG: CC1, CC2 → CH224D (no pull-downs)
Result: PD negotiation fails!
CORRECT: CC1 → 5.1kΩ → GND, CC2 → 5.1kΩ → GND
Result: Identified as sink, negotiation works!
❌ Mistake 3: Using wrong Rset value
WRONG: Rset = 24kΩ → requests 12V instead of 15V!
CORRECT: Rset = 56kΩ → requests 15V ✅
❌ Mistake 4: Not shorting DP to DM with 6-pin connector
WRONG: DP and DM left floating
Result: IC may behave unpredictably
CORRECT: DP (pin 8) shorted to DM (pin 9)
Result: PD-only mode works correctly
❌ Mistake 5: Forgetting VDD decoupling capacitor
WRONG: VDD pin with no capacitor
Result: Unstable operation, oscillation
CORRECT: VDD → 1µF cap → GND
Result: Stable internal regulator
Why CH224D is Perfect for This Project
Our modular synth power supply needs:
- ✅ 15V from USB-C PD → CH224D negotiates this automatically
- ✅ Simple configuration → Just one 56kΩ resistor
- ✅ No microcontroller → Standalone operation
- ✅ Power-only application → 6-pin connector sufficient
- ✅ Up to 45W (15V × 3A) → Enough for our DC-DC converters
- ✅ JLCPCB compatible → SMD package, good stock
Alternative approaches would be worse:
- ❌ Fixed 12V adapter → Less portable, requires wall outlet
- ❌ USB-C to DC barrel cable → Only 20V max, needs extra converter
- ❌ PD trigger boards → Usually larger, more expensive
- ❌ Microcontroller-based PD → Complex, overkill for fixed voltage
CH224D = Perfect balance of simplicity and functionality!
Related Documentation
- CH224D Component Page - Full specifications and pinout
- J1 USB-C Connector - Connector specifications
- Diagram1: USB-PD Section - Complete circuit
- USB Type-C Pinout - Understanding USB-C pins
- CH224D Datasheet - Official datasheet
References
- CH224D Datasheet - WCH Official
- USB Power Delivery Specification 3.1 - USB-IF
- USB Type-C Specification - USB-IF