# TXB0104PWR Datasheet Reference

Based on the official TXB0104 datasheet: [TXB0104 Datasheet](https://www.ti.com/lit/ds/symlink/txb0104.pdf)

## Key Specifications

### Power Supply Requirements

- **VCCA (A Port):** 1.2V to 3.6V
  - **Our design:** 3.3V (for ESP32)
  - **Pin:** Pin 12 (VCCA)
- **VCCB (B Port):** 1.65V to 5.5V
  - **Our design:** 5V (for AC communication)
  - **Pin:** Pin 11 (VCCB)
- **Critical:** VCCA must NOT exceed VCCB
  - **Our design:** 3.3V ≤ 5V ✓ (correct)

### Pin Configuration (TSSOP-14 Package - TXB0104PW)

| Pin | Name | Function | Our Connection |
|-----|------|----------|----------------|
| 1 | A1 | A Port 1 (Low Voltage) | ESP32 GPIO17 (TX) |
| 2 | A2 | A Port 2 (Low Voltage) | ESP32 GPIO16 (RX) |
| 3 | A3 | A Port 3 (Low Voltage) | NC (Not Connected) |
| 4 | A4 | A Port 4 (Low Voltage) | NC (Not Connected) |
| 5 | GND | Ground | GND |
| 6 | B4 | B Port 4 (High Voltage) | NC (Not Connected) |
| 7 | B3 | B Port 3 (High Voltage) | NC (Not Connected) |
| 8 | B2 | B Port 2 (High Voltage) | AC TX (J1 Pin 3) |
| 9 | B1 | B Port 1 (High Voltage) | AC RX (J1 Pin 2) |
| 10 | OE | Output Enable | +3V3 (VCCA) |
| 11 | VCCB | B Port Power Supply | +5V |
| 12 | VCCA | A Port Power Supply | +3V3 |
| 13 | GND | Ground | GND |
| 14 | GND | Ground | GND |

### Critical Design Requirements

#### 1. Output Enable (OE) Pin

**Per Datasheet:**
- **OE input circuit is referenced to VCCA** (not VCCB)
- **When OE is LOW:** All outputs are in high-impedance state
- **When OE is HIGH:** Device is enabled
- **Power-up/down:** OE must be tied to GND through a pulldown resistor to ensure high-impedance during power transitions

**Our Design:**
- **OE (Pin 10):** Connected to +3V3 (VCCA) ✓
- **Note:** We connect OE directly to VCCA (3.3V), which keeps the device always enabled
- **Alternative:** Could add pulldown resistor for power-up safety, but direct connection to VCCA is acceptable for always-on operation

**Recommendation:**
- Current design (OE → +3V3) is correct for always-enabled operation
- Optional: Add 10kΩ pulldown resistor from OE to GND for power-up safety (not critical if power sequencing is controlled)

#### 2. Power Supply Sequencing

**Per Datasheet:**
- VCCA must not exceed VCCB
- VCC isolation: If either VCC input is at GND, all outputs are in high-impedance state
- IOFF supports partial power-down mode

**Our Design:**
- VCCA = 3.3V, VCCB = 5V ✓ (3.3V ≤ 5V, correct)
- Both supplies come from same source (J1 Pin 1 = +5V)
- 3.3V is derived from 5V via regulator
- Power sequencing: 5V comes first, then 3.3V (via regulator) - this is acceptable

#### 3. Bidirectional Translation

**Per Datasheet:**
- Automatic direction sensing
- No direction control needed
- Works bidirectionally on A and B ports

**Our Design:**
- A1 (Pin 1) ↔ B1 (Pin 9): ESP32 TX ↔ AC RX ✓
- A2 (Pin 2) ↔ B2 (Pin 8): ESP32 RX ↔ AC TX ✓
- Automatic direction sensing handles UART communication ✓

#### 4. Decoupling Capacitors

**Per Datasheet:**
- Recommended: 0.1µF (100nF) ceramic capacitor on VCCA
- Recommended: 0.1µF (100nF) ceramic capacitor on VCCB
- Place as close as possible to power pins

**Our Design:**
- VCCA (Pin 12): Should have 100nF capacitor to GND
- VCCB (Pin 11): Should have 100nF capacitor to GND
- **Note:** These are not explicitly listed in our component list - should be added

**Recommendation:**
- Add C14: 100nF from VCCA (Pin 12) to GND
- Add C15: 100nF from VCCB (Pin 11) to GND

### Electrical Characteristics

- **Low Power Consumption:** 5µA maximum ICC
- **ESD Protection:** ±15kV on B port
- **Latch-up Performance:** Exceeds 100mA per JESD 78, Class II
- **Operating Temperature:** -40°C to +85°C

### Package Information

**TXB0104PW (TSSOP-14):**
- **Package:** TSSOP (14-pin)
- **Body Size:** 5.00mm × 4.40mm
- **Height:** 1.2mm max
- **Lead Pitch:** 0.65mm (fine pitch)
- **Footprint:** `Package_SO:TSSOP-14_4.4x5mm_P0.65mm` ✓

### PCB Layout Recommendations

**Per Datasheet:**
1. **Decoupling capacitors:** Place 100nF ceramic capacitors as close as possible to VCCA and VCCB pins
2. **Ground plane:** Use ground plane for GND pins (5, 13, 14)
3. **Trace routing:** Keep A and B port traces short and matched length if possible
4. **Thermal:** No special thermal considerations needed (low power device)

### Design Verification

**Our Design vs Datasheet:**

| Requirement | Datasheet | Our Design | Status |
|-------------|-----------|------------|--------|
| VCCA voltage | 1.2V to 3.6V | 3.3V | ✓ |
| VCCB voltage | 1.65V to 5.5V | 5V | ✓ |
| VCCA ≤ VCCB | Required | 3.3V ≤ 5V | ✓ |
| OE connection | VCCA referenced | +3V3 (VCCA) | ✓ |
| Package | TSSOP-14 | TSSOP-14 | ✓ |
| Decoupling caps | 100nF on VCCA/VCCB | **Missing** | ⚠️ Should add |

### Missing Components

**Should Add:**
- **C14:** 100nF ceramic capacitor from VCCA (Pin 12) to GND
- **C15:** 100nF ceramic capacitor from VCCB (Pin 11) to GND

**Optional (for power-up safety):**
- **R7:** 10kΩ pulldown resistor from OE (Pin 10) to GND (optional, not critical)

### References

- **Official Datasheet:** [TXB0104 Datasheet](https://www.ti.com/lit/ds/symlink/txb0104.pdf)
- **Package Information:** TSSOP-14 (TXB0104PW)
- **Application Note:** See datasheet section 8 for typical applications