150 lines
5.2 KiB
Markdown
150 lines
5.2 KiB
Markdown
# TXB0104PWR Datasheet Reference
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Based on the official TXB0104 datasheet: [TXB0104 Datasheet](https://www.ti.com/lit/ds/symlink/txb0104.pdf)
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## Key Specifications
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### Power Supply Requirements
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- **VCCA (A Port):** 1.2V to 3.6V
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- **Our design:** 3.3V (for ESP32)
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- **Pin:** Pin 12 (VCCA)
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- **VCCB (B Port):** 1.65V to 5.5V
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- **Our design:** 5V (for AC communication)
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- **Pin:** Pin 11 (VCCB)
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- **Critical:** VCCA must NOT exceed VCCB
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- **Our design:** 3.3V ≤ 5V ✓ (correct)
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### Pin Configuration (TSSOP-14 Package - TXB0104PW)
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| Pin | Name | Function | Our Connection |
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|-----|------|----------|----------------|
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| 1 | A1 | A Port 1 (Low Voltage) | ESP32 GPIO17 (TX) |
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| 2 | A2 | A Port 2 (Low Voltage) | ESP32 GPIO16 (RX) |
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| 3 | A3 | A Port 3 (Low Voltage) | NC (Not Connected) |
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| 4 | A4 | A Port 4 (Low Voltage) | NC (Not Connected) |
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| 5 | GND | Ground | GND |
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| 6 | B4 | B Port 4 (High Voltage) | NC (Not Connected) |
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| 7 | B3 | B Port 3 (High Voltage) | NC (Not Connected) |
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| 8 | B2 | B Port 2 (High Voltage) | AC TX (J1 Pin 3) |
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| 9 | B1 | B Port 1 (High Voltage) | AC RX (J1 Pin 2) |
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| 10 | OE | Output Enable | +3V3 (VCCA) |
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| 11 | VCCB | B Port Power Supply | +5V |
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| 12 | VCCA | A Port Power Supply | +3V3 |
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| 13 | GND | Ground | GND |
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| 14 | GND | Ground | GND |
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### Critical Design Requirements
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#### 1. Output Enable (OE) Pin
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**Per Datasheet:**
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- **OE input circuit is referenced to VCCA** (not VCCB)
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- **When OE is LOW:** All outputs are in high-impedance state
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- **When OE is HIGH:** Device is enabled
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- **Power-up/down:** OE must be tied to GND through a pulldown resistor to ensure high-impedance during power transitions
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**Our Design:**
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- **OE (Pin 10):** Connected to +3V3 (VCCA) ✓
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- **Note:** We connect OE directly to VCCA (3.3V), which keeps the device always enabled
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- **Alternative:** Could add pulldown resistor for power-up safety, but direct connection to VCCA is acceptable for always-on operation
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**Recommendation:**
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- Current design (OE → +3V3) is correct for always-enabled operation
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- Optional: Add 10kΩ pulldown resistor from OE to GND for power-up safety (not critical if power sequencing is controlled)
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#### 2. Power Supply Sequencing
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**Per Datasheet:**
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- VCCA must not exceed VCCB
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- VCC isolation: If either VCC input is at GND, all outputs are in high-impedance state
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- IOFF supports partial power-down mode
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**Our Design:**
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- VCCA = 3.3V, VCCB = 5V ✓ (3.3V ≤ 5V, correct)
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- Both supplies come from same source (J1 Pin 1 = +5V)
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- 3.3V is derived from 5V via regulator
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- Power sequencing: 5V comes first, then 3.3V (via regulator) - this is acceptable
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#### 3. Bidirectional Translation
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**Per Datasheet:**
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- Automatic direction sensing
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- No direction control needed
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- Works bidirectionally on A and B ports
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**Our Design:**
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- A1 (Pin 1) ↔ B1 (Pin 9): ESP32 TX ↔ AC RX ✓
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- A2 (Pin 2) ↔ B2 (Pin 8): ESP32 RX ↔ AC TX ✓
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- Automatic direction sensing handles UART communication ✓
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#### 4. Decoupling Capacitors
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**Per Datasheet:**
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- Recommended: 0.1µF (100nF) ceramic capacitor on VCCA
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- Recommended: 0.1µF (100nF) ceramic capacitor on VCCB
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- Place as close as possible to power pins
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**Our Design:**
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- VCCA (Pin 12): Should have 100nF capacitor to GND
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- VCCB (Pin 11): Should have 100nF capacitor to GND
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- **Note:** These are not explicitly listed in our component list - should be added
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**Recommendation:**
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- Add C14: 100nF from VCCA (Pin 12) to GND
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- Add C15: 100nF from VCCB (Pin 11) to GND
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### Electrical Characteristics
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- **Low Power Consumption:** 5µA maximum ICC
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- **ESD Protection:** ±15kV on B port
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- **Latch-up Performance:** Exceeds 100mA per JESD 78, Class II
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- **Operating Temperature:** -40°C to +85°C
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### Package Information
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**TXB0104PW (TSSOP-14):**
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- **Package:** TSSOP (14-pin)
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- **Body Size:** 5.00mm × 4.40mm
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- **Height:** 1.2mm max
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- **Lead Pitch:** 0.65mm (fine pitch)
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- **Footprint:** `Package_SO:TSSOP-14_4.4x5mm_P0.65mm` ✓
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### PCB Layout Recommendations
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**Per Datasheet:**
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1. **Decoupling capacitors:** Place 100nF ceramic capacitors as close as possible to VCCA and VCCB pins
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2. **Ground plane:** Use ground plane for GND pins (5, 13, 14)
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3. **Trace routing:** Keep A and B port traces short and matched length if possible
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4. **Thermal:** No special thermal considerations needed (low power device)
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### Design Verification
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**Our Design vs Datasheet:**
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| Requirement | Datasheet | Our Design | Status |
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|-------------|-----------|------------|--------|
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| VCCA voltage | 1.2V to 3.6V | 3.3V | ✓ |
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| VCCB voltage | 1.65V to 5.5V | 5V | ✓ |
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| VCCA ≤ VCCB | Required | 3.3V ≤ 5V | ✓ |
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| OE connection | VCCA referenced | +3V3 (VCCA) | ✓ |
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| Package | TSSOP-14 | TSSOP-14 | ✓ |
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| Decoupling caps | 100nF on VCCA/VCCB | **Missing** | ⚠️ Should add |
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### Missing Components
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**Should Add:**
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- **C14:** 100nF ceramic capacitor from VCCA (Pin 12) to GND
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- **C15:** 100nF ceramic capacitor from VCCB (Pin 11) to GND
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**Optional (for power-up safety):**
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- **R7:** 10kΩ pulldown resistor from OE (Pin 10) to GND (optional, not critical)
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### References
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- **Official Datasheet:** [TXB0104 Datasheet](https://www.ti.com/lit/ds/symlink/txb0104.pdf)
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- **Package Information:** TSSOP-14 (TXB0104PW)
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- **Application Note:** See datasheet section 8 for typical applications
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