# PCA9306 Level Shifter Molecule — Plan

## Brief
Drop-in I²C / SMBus voltage-level translator molecule for Adom workcells. Bridges a 1.8 V bus to a 3.3 V (or up to 5 V) bus with no direction pin and **no one-shot accelerator contention** — the canonical replacement for the TXS0108E on the Bosch sensortec arm board, where the TXS family's one-shot rising-edge accelerator fights I²C slave open-drain ACK pull-down and produces address-NACK at probe time.

## Decisions
- **Tool:** adom-tsci / tscircuit (canonical Adom path).
- **Size:** `24x16` — 4-pin molecule. Wider than tall so 4 + 4 perimeter contacts fit comfortably.
- **Pin grid:** medium machine pins (4 corner pins + 4 edge contacts per long side).
- **IC:** TI PCA9306DCUR in VSSOP-8 (DCU package). LCSC C58662 (JLC extended).
- **EN handling:** internally tied to VREF2 via a 10 kΩ pull-up (always-enabled by default). Cut the R5 trace if external EN control is needed later.
- **Pull-ups:** 4.7 kΩ on SDA1, SCL1 → VREF1; 4.7 kΩ on SDA2, SCL2 → VREF2. UNI-ROYAL 0402 (LCSC C25900 — JLC basic).
- **Decoupling:** one 100 nF 0402 X7R on each VREF rail, placed within 1 mm of the IC pin. Samsung CL05B104KO5NNNC (LCSC C1525 — JLC basic).
- **Top silkscreen:** "PCA9306", function tag, pin labels on every contact.
- **Bottom silkscreen:** part name, "1.8V <-> 3.3V I2C", version + author + date.

## Components
| Ref | Value | Package | MPN | LCSC |
|-----|-------|---------|-----|------|
| U1  | PCA9306DCUR | VSSOP-8 | PCA9306DCUR | C58662 |
| C1, C2 | 100 nF 25 V X7R | 0402 | CL05B104KO5NNNC | C1525 |
| R1..R4 | 4.7 kΩ 1 % | 0402 | 0402WGF4701TCE | C25900 |
| R5 | 10 kΩ 1 % | 0402 | 0402WGF1002TCE | C25744 |

## Workcell interface (8 medium machine contacts)
| Pin | Net   | Side  | Notes |
|-----|-------|-------|-------|
| MC_VREF1 | VREF1 | left (LV) | 1.71–1.89 V supply |
| MC_SDA1  | SDA1  | left | 1.8 V SDA, 4.7 kΩ to VREF1 |
| MC_SCL1  | SCL1  | left | 1.8 V SCL, 4.7 kΩ to VREF1 |
| MC_GND1  | GND   | left | shared ground |
| MC_VREF2 | VREF2 | right (HV) | 3.3 V supply |
| MC_SDA2  | SDA2  | right | 3.3 V SDA, 4.7 kΩ to VREF2 |
| MC_SCL2  | SCL2  | right | 3.3 V SCL, 4.7 kΩ to VREF2 |
| MC_GND2  | GND   | right | shared ground |

## Don'ts
- No BGA / 0201.
- No external EN pin.
- Only one JLC extended part (U1 itself); everything else basic-tier.

## Publish
```bash
cd ~/project/adom-tsci-projects/pca9306-level-shifter
bun install
bunx tsci build lib/index.tsx --glbs --svgs --3d-png --pcb-png
adom-tsci start .
adom-tsci export-wiki --slug pca9306-level-shifter --page-type molecules
```