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USB-C 5V Input

@electrace/usb-c-power@1.0.0 · CC-BY-4.0
vin 5 Vvout 5 Viout_max 3 A
The actual schematic inside this block — every part is explained below.

USB-C 5V Input

Turns a USB-C receptacle into a clean 5 V rail — including the one thing everyone forgets: without the two CC resistors, a USB-C charger gives you nothing. A USB-C source keeps VBUS off until it sees a sink advertise itself on the CC pins.

  • R1 / R2 — 5.1 kΩ pulldowns, one per CC pin. This is the entire "handshake" for a 5 V device: the resistor tells the source "I'm a default-power sink — turn VBUS on." You need one on each CC pin because the cable can plug in either way; only one is actually used per orientation, but you never know which.
  • D1 — a TVS on VBUS. Hot-plugging a cable rings; the clamp eats the spike before your regulator sees it.
  • C1 — input bulk capacitance, so a sudden load step doesn't sag the rail through the cable's resistance.

How much current you get is the source's decision, advertised on CC: a basic port gives 0.5–1.5 A, a 15 W source gives 3 A. The pulldowns can't negotiate more — and that's a feature: a sink that can't ask for higher voltage can never receive more than 5 V.

Exposes: vbus, cc1, cc2, gnd (dock these to a USB-C receptacle) and vout (+5 V, up to 3 A).

⚠ If your board mysteriously won't power from a C-to-C cable but works from A-to-C, it's missing CC pulldowns — A-to-C cables hardwire VBUS, C-to-C sources wait for the handshake. This block is the fix.

Exposed nets

●vbusin · power · 4.75–5.25 V
●cc1in · signal
●cc2in · signal
●gndin · gnd
●voutout · rail · 5 V

Inside this block

R1
5.1k
CC1 pulldown — tells the source 'I'm a 5 V sink, give me what you can'
R2
5.1k
CC2 pulldown — the cable can flip, so BOTH CC pins need one
D1
tvs
clamps VBUS spikes from cable hot-plug before they reach the rail
C1
22uF
input bulk — rides through the source's cable drop on load steps

Limits & gotchas

⚠iout.max 3A — 3 A only when the source advertises it on CC. With plain 5.1 kΩ pulldowns you take what the charger offers — budget for 0.5–1.5 A from a basic port, 3 A from a 15 W source.
⚠vin.max 5.5V — This is a 5 V-only sink. A PD source never sends more than 5 V unless ASKED on CC — these pulldowns can't ask, which is exactly what keeps the rail safe at 5 V.
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