# TPS562201 12V → 3.3V Buck Molecule

A 24 × 16 mm 4-pin power brick based on TI's **TPS562201** synchronous buck converter. Takes **12 V** in on the left-edge contacts, delivers **3.3 V at up to 500 mA** on the right-edge contacts. Silicon is rated for 3 A so 500 mA sits at ~6× thermal headroom — the board runs cool under spec.

Shipping as an adom-tsci example, fully interactive in the Hydrogen webview (3D / PCB / Schematic / Parts tabs, Inspect + Measure tools, deterministic Walkthrough Demo).

## Why this board exists

Most power-sourcing flows in Adom need a clean 3.3 V rail. Rather than re-inventing that on every new project, this is the reference molecule: drop it into a workcell layout, connect VIN and GND, pull 3.3 V off the output pins. Also serves as the canonical "simple DC-DC" example for anyone learning the tscircuit / adom-tsci stack.

## The components

| Ref | Value | Footprint | Role |
|---|---|---|---|
| U1 | TPS562201 | SOT-23-6 | Synchronous buck. Internal MOSFETs, internal compensation, 580 kHz switching, 4.5–17 V input. |
| C1 | 10 µF / 25 V | 0805 | Input cap — absorbs VIN ripple when the high-side MOSFET switches on. |
| L1 | 2.2 µH shielded / 3 A | 0805 | Energy-transfer inductor. Ripple ≈ 30 % of Iout_max at 580 kHz — sweet spot between core size and filter burden. |
| C3 | 22 µF / 10 V | 0805 | Output cap — smooths the switching waveform, handles load steps. |
| C2 | 100 nF / 25 V | 0402 | Bootstrap cap — drives the high-side gate. |
| R1 | 45.3 kΩ (E96) | 0402 | Feedback-divider top. |
| R2 | 10 kΩ | 0402 | Feedback-divider bottom. `Vout = 0.596 × (1 + R1/R2) = 3.296 V` → exactly **3.3 V** to one decimal. |
| R3 | 100 kΩ | 0402 | EN pull-up — rail is always-on. Replace with a GPIO trace if the host should gate the rail. |

**External pins** (24 × 16 mm brick):

- Left edge: **VIN (12 V)** and **GND**
- Right edge: **VCC (3.3 V)** and **GND**

Two GND pins so the return path through a workcell jig is low-impedance on both sides.

**Test points** (probing workcell):

- `TP_VIN` / `TP_VCC` — steady DC verification
- `TP_GND` — reference
- `TP_SW` — **scope probe point**. Carries the switching waveform (12 V → 0 V rectangles at 580 kHz). Fastest way to confirm the converter is running / stuck / oscillating.

## Mouser BOM

Fort Worth drone delivery, Mouser-preferred per Adom sourcing defaults.

| Ref | MPN | Mouser P/N | Stock | Unit @ 1 |
|---|---|---|---|---|
| U1 | TPS562201DDCR | 595-TPS562201DDCR | 27,479 | $0.39 |
| L1 | Coilcraft XFL3012-222ME (2.2 µH / 3 A) | 994-XFL3012-222ME | 5k+ | ~$0.90 |
| C1 | 10 µF 25 V X5R 0805 (jelly-bean) | any | 10k+ | ~$0.30 |
| C3 | 22 µF 10 V X5R 0805 (jelly-bean) | any | 10k+ | ~$0.25 |
| C2 | 100 nF 25 V X7R 0402 | any | — | <$0.05 |
| R1 | 45.3 kΩ 1 % 0402 (E96) | any | — | <$0.05 |
| R2 | 10 kΩ 1 % 0402 | any | — | <$0.05 |
| R3 | 100 kΩ 1 % 0402 | any | — | <$0.05 |

Rough BOM cost: ~**$2.00** in singles, ~**$1.25** at 100×. All parts Mouser-stocked, Fort Worth drone-deliverable in 40 min.

## Running it locally

```bash
# clone adom-tsci (or install from the wiki) and launch the example
git clone https://github.com/adom-inc/adom-tsci
cd adom-tsci/examples/TPS562201-12V-to-3V3-Molecule
bun install
adom-tsci start . --port 8889
# A Hydrogen webview tab opens showing 3D / PCB / Schematic / Parts.
```

Or directly against the installed adom-tsci:

```bash
adom-tsci start ~/project/adom-tsci/examples/TPS562201-12V-to-3V3-Molecule --port 8889
```

## Design review notes

- **Vref is 0.596 V**, not 0.8 V like some TI bucks. If you swap R1/R2 to retune, use this ratio: `Rtop/Rbot = (Vout / 0.596) − 1`.
- **EN pulled high via 100 kΩ** — rail is always-on. If you need GPIO-gated startup, break R3 and route EN to a host pin. Add a 100 nF cap from EN to GND if the control signal is noisy.
- **Bootstrap cap on SW ↔ VBST** is *required*, not optional. The high-side MOSFET gate driver is charge-pumped from this cap. Don't omit.
- **The two GND pins** aren't just aesthetic — they pair with VIN and VCC on opposite edges so a jig fixture can route both sides' return current independently. Keeps ground loops out of whatever signal chain is sharing the workcell.

## Changelog

- **v1.0.0 (2026-04)** — initial ship: 3.3 V @ 500 mA, 45.3 k / 10 k divider (exact 3.30 V), 4-pin brick, 4 testpoints, bottom-silk ID card. Provenance-stamped walkthrough.

## Source

[adom-inc/adom-tsci · examples/TPS562201-12V-to-3V3-Molecule](https://github.com/adom-inc/adom-tsci/tree/master/examples/TPS562201-12V-to-3V3-Molecule)