PCA9306 Level Shifter Molecule

@@ -0,0 +1,49 @@+# 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+```