test
This commit is contained in:
232
Midea_ESP/TRACE_WIDTH_GUIDE.md
Normal file
232
Midea_ESP/TRACE_WIDTH_GUIDE.md
Normal file
@@ -0,0 +1,232 @@
|
||||
# Trace Width Guide: Power Distribution
|
||||
|
||||
**Date:** 2025-12-28
|
||||
**Based on:** ESP32-WROOM-32E, AMS1117-3.3, TXB0104PWR
|
||||
|
||||
---
|
||||
|
||||
## Current Requirements Summary
|
||||
|
||||
### 3.3V Power Rail
|
||||
- **ESP32 peak current:** 500mA (WiFi transmission)
|
||||
- **LEDs (2×):** ~12mA
|
||||
- **TXB0104 VCCA:** 5µA (negligible)
|
||||
- **Pull-up resistors:** <0.1mA (negligible)
|
||||
- **Total peak current:** **~512mA**
|
||||
|
||||
### 5V Power Rail
|
||||
- **TXB0104 VCCB:** 5µA (negligible)
|
||||
- **AC Connector:** Minimal (if just signaling)
|
||||
- **Total current:** **~10mA** (very low)
|
||||
|
||||
---
|
||||
|
||||
## Trace Width Calculations
|
||||
|
||||
### IPC-2221 Standard Reference
|
||||
|
||||
**Current Carrying Capacity (10°C temperature rise):**
|
||||
|
||||
| Copper Weight | Layer Type | Capacity |
|
||||
|---------------|------------|----------|
|
||||
| 1oz (35µm) | External (F.Cu/B.Cu) | ~1.0A per 1mm width |
|
||||
| 1oz (35µm) | Internal | ~0.5A per 1mm width |
|
||||
| 2oz (70µm) | External | ~2.0A per 1mm width |
|
||||
| 2oz (70µm) | Internal | ~1.0A per 1mm width |
|
||||
|
||||
---
|
||||
|
||||
## Recommended Trace Widths
|
||||
|
||||
### For Standard 1oz Copper PCB (Most Common)
|
||||
|
||||
#### 3.3V Power Traces
|
||||
|
||||
**Minimum Requirements:**
|
||||
- **External layer:** 0.51mm (for 512mA)
|
||||
- **Internal layer:** 1.02mm (for 512mA)
|
||||
|
||||
**Recommended (with safety margin):**
|
||||
- **External layer:** **1.0mm** (50% margin, easy to route)
|
||||
- **Internal layer:** **1.5mm** (50% margin)
|
||||
|
||||
**Best Practice:**
|
||||
- **Main power rail:** Use **1.0mm to 1.5mm** wide traces
|
||||
- **Branch traces:** Can be narrower (0.5mm) for short runs to components
|
||||
- **Copper zones/pours:** Even better for power distribution
|
||||
|
||||
#### 5V Power Traces
|
||||
|
||||
**Minimum Requirements:**
|
||||
- **Any layer:** 0.01mm (for 10mA) - theoretical minimum
|
||||
|
||||
**Recommended:**
|
||||
- **Standard signal width:** **0.3mm** (sufficient and standard)
|
||||
- **Main rail:** **0.5mm** (if using dedicated trace)
|
||||
|
||||
**Note:** 5V current is very low, so trace width is not critical. Use standard signal trace width (0.2-0.3mm) or slightly wider (0.5mm) for main rail.
|
||||
|
||||
---
|
||||
|
||||
## Detailed Recommendations
|
||||
|
||||
### 3.3V Power Distribution
|
||||
|
||||
#### Option 1: Wide Traces (Recommended)
|
||||
```
|
||||
Main 3.3V rail: 1.0mm - 1.5mm width
|
||||
Branch to ESP32: 0.8mm - 1.0mm width
|
||||
Branch to LEDs: 0.3mm - 0.5mm width
|
||||
Branch to TXB0104: 0.3mm - 0.5mm width
|
||||
```
|
||||
|
||||
#### Option 2: Copper Zones/Pours (Best Practice)
|
||||
- Create a **3.3V copper zone** covering the board area
|
||||
- Provides lowest impedance
|
||||
- Best for power distribution
|
||||
- Use **1.0mm clearance** from other nets
|
||||
|
||||
#### Option 3: Hybrid Approach
|
||||
- Main rail: **1.5mm wide trace** from regulator to ESP32 area
|
||||
- Copper zone: **3.3V zone** around ESP32 and other components
|
||||
- Branch traces: **0.5mm** for short connections
|
||||
|
||||
### 5V Power Distribution
|
||||
|
||||
```
|
||||
Main 5V rail: 0.3mm - 0.5mm width (sufficient)
|
||||
Branch to TXB0104: 0.3mm width (standard)
|
||||
Branch to AC Conn: 0.3mm width (standard)
|
||||
```
|
||||
|
||||
**Note:** 5V current is so low that trace width is not a concern. Use standard signal trace widths.
|
||||
|
||||
---
|
||||
|
||||
## Implementation Guidelines
|
||||
|
||||
### For KiCad PCB Layout
|
||||
|
||||
#### Setting Up Trace Widths
|
||||
|
||||
1. **Design Rules Setup:**
|
||||
- Go to: `File → Board Setup → Design Rules → Net Classes`
|
||||
- Create net classes:
|
||||
- `Power_3V3`: Min width 0.5mm, Preferred 1.0mm, Max 2.0mm
|
||||
- `Power_5V`: Min width 0.2mm, Preferred 0.3mm, Max 1.0mm
|
||||
- `Signal`: Min width 0.2mm, Preferred 0.2mm, Max 0.5mm
|
||||
|
||||
2. **Assign Net Classes:**
|
||||
- `+3.3V` net → `Power_3V3` class
|
||||
- `+5V` net → `Power_5V` class
|
||||
- All other nets → `Signal` class
|
||||
|
||||
3. **Routing:**
|
||||
- Route power traces first (widest)
|
||||
- Use copper zones for power distribution where possible
|
||||
- Keep power traces short and direct
|
||||
|
||||
### Trace Width by Location
|
||||
|
||||
| Location | 3.3V Width | 5V Width | Notes |
|
||||
|----------|------------|----------|-------|
|
||||
| **Regulator output** | 1.0-1.5mm | - | Main power source |
|
||||
| **To ESP32 VDD** | 1.0mm | - | High current path |
|
||||
| **To TXB0104 VCCA** | 0.5mm | - | Low current |
|
||||
| **To LEDs** | 0.3-0.5mm | - | Low current |
|
||||
| **To pull-ups** | 0.2-0.3mm | - | Very low current |
|
||||
| **5V main rail** | - | 0.3-0.5mm | Low current |
|
||||
| **To TXB0104 VCCB** | - | 0.3mm | Very low current |
|
||||
|
||||
---
|
||||
|
||||
## Copper Zone Recommendations
|
||||
|
||||
### 3.3V Copper Zone
|
||||
- **Layer:** F.Cu or B.Cu (or both)
|
||||
- **Clearance:** 0.5mm from other nets
|
||||
- **Min width:** 0.5mm (for narrow areas)
|
||||
- **Coverage:** Around ESP32, regulator, and power distribution area
|
||||
|
||||
### GND Copper Zone
|
||||
- **Layer:** Both F.Cu and B.Cu (ground plane)
|
||||
- **Clearance:** 0.3mm from other nets
|
||||
- **Coverage:** Entire board (ground plane)
|
||||
- **Vias:** Connect both layers with multiple vias
|
||||
|
||||
### 5V Copper Zone (Optional)
|
||||
- **Not necessary** due to very low current
|
||||
- Can use if board space allows
|
||||
- **Width:** 0.3mm minimum if used
|
||||
|
||||
---
|
||||
|
||||
## Thermal Considerations
|
||||
|
||||
### Power Dissipation
|
||||
- **3.3V @ 512mA:** ~1.69W (ESP32 peak)
|
||||
- **Trace resistance:** Lower with wider traces
|
||||
- **Voltage drop:** Minimize with wide traces and short paths
|
||||
|
||||
### Trace Heating
|
||||
With 1.0mm trace width and 512mA:
|
||||
- **Temperature rise:** ~10°C (acceptable)
|
||||
- **Voltage drop:** <50mV for typical trace lengths
|
||||
|
||||
---
|
||||
|
||||
## Design Checklist
|
||||
|
||||
- [ ] 3.3V main rail: **1.0mm minimum** (1.5mm preferred)
|
||||
- [ ] 3.3V to ESP32: **1.0mm minimum**
|
||||
- [ ] 3.3V branches: **0.5mm minimum** for short runs
|
||||
- [ ] 5V traces: **0.3mm minimum** (standard signal width)
|
||||
- [ ] Ground plane: **Full coverage** on one or both layers
|
||||
- [ ] Power zones: Consider copper zones for 3.3V
|
||||
- [ ] Vias: Use multiple vias for layer transitions on power nets
|
||||
- [ ] Clearance: Maintain proper clearance from other nets
|
||||
|
||||
---
|
||||
|
||||
## Quick Reference
|
||||
|
||||
### Minimum Trace Widths (1oz copper, external layer)
|
||||
|
||||
| Net | Current | Minimum | Recommended |
|
||||
|-----|---------|---------|-------------|
|
||||
| **+3.3V** | 512mA | 0.51mm | **1.0mm** |
|
||||
| **+5V** | 10mA | 0.01mm | **0.3mm** |
|
||||
| **GND** | - | - | **Ground plane** |
|
||||
| **Signals** | <10mA | 0.2mm | **0.2mm** |
|
||||
|
||||
### Summary
|
||||
- **3.3V traces:** Use **1.0mm** width (or copper zone)
|
||||
- **5V traces:** Use **0.3mm** width (standard signal width)
|
||||
- **GND:** Use **ground plane** (copper zone covering entire board)
|
||||
|
||||
---
|
||||
|
||||
## Additional Notes
|
||||
|
||||
### Why 1.0mm for 3.3V?
|
||||
- Provides **50% safety margin** over minimum requirement
|
||||
- Easy to route and manufacture
|
||||
- Low voltage drop
|
||||
- Good thermal performance
|
||||
- Standard practice for power traces
|
||||
|
||||
### Why 0.3mm for 5V?
|
||||
- Current is very low (10mA)
|
||||
- Standard signal trace width
|
||||
- Easy to route
|
||||
- Sufficient for the application
|
||||
|
||||
### Copper Zones vs Traces
|
||||
- **Copper zones:** Best for power distribution (lowest impedance)
|
||||
- **Traces:** Good for point-to-point connections
|
||||
- **Hybrid:** Use zones for main distribution, traces for branches
|
||||
|
||||
---
|
||||
|
||||
*Guide created: 2025-12-28*
|
||||
|
||||
Reference in New Issue
Block a user