NodeLoop
USB PD 3.2 planning tool

USB-C PD Contract Checker: Source, Cable and Sink

Check whether the advertised source capabilities, selected cable, and requested sink load form a valid contract. The result separates voltage support, cable mode, current budget, power limit, and safe startup behavior.

Tool Published Jul 15, 2026 Reviewed against USB-IF 2026 specifications
Hardware design guide USB-C pinout

USB-C PD baseline limits

Attach baseline
Safe 5 V before a PD contract
SPR ceiling
Up to 100 W
EPR ceiling
Up to 240 W
Cable gate
E-marker above 3 A; EPR identity for EPR Mode

Reference scenarios

Load a known profile

Replace every value with the real controller and cable capabilities.

Declared capabilities

Model what the source and cable actually advertise, not the connector logo.

Advertised fixed PDOs

5 V is mandatory in this profile. Check only the PDOs present in Source_Capabilities.

W
A

Sink request

V
A

Result

Checking...

--
Contract voltage
--
Available current
--
Available power
--
Requested power
--

Negotiation mode

--

--

5 V fallback budget

--

Fallback is a power ceiling, not permission to enable a load that cannot operate safely at 5 V.

Contract checks

Hard limit: this checker evaluates declared capabilities and first-order electrical limits. It does not validate CC behavior, message timing, cable identity responses, OVP/OCP, transients, connector heating, layout, firmware policy, or USB-IF compliance.

Model boundaries

What each source mode means

Mode Voltage behavior Power range Checker assumption
Type-C current 5 V at default, 1.5 A, or 3 A advertisement Up to 15 W No explicit PD contract
SPR fixed Only the selected 5, 9, 15, or 20 V PDOs Up to 100 W The requested voltage must match a checked PDO
SPR PPS 5 V to 11, 16, or 21 V maximum in 20 mV steps Up to 100 W PDP and current limit still cap the result
SPR AVS 9-15 V or 9-20 V in 100 mV steps Up to 100 W PPS support does not imply AVS support
EPR fixed / AVS 28, 36, 48 V fixed; AVS from 15 V to the advertised EPR maximum Above 100 W, up to 240 W PDP EPR Mode requires an EPR-capable source, sink, controller path, and cable

Before schematic sign-off

  • Confirm the controller datasheet explicitly supports every selected PDO or APDO mode.
  • Gate the main load until the PD controller reports an active contract.
  • Rate capacitors, FETs, eFuses, TVS/OVP, discharge paths, and spacing for the real VBUS envelope plus design margin.
  • Verify cable identity handling before allowing more than 3 A or entering EPR Mode.
  • Test detach, brownout, source reset, rejected requests, fallback, short circuit, and hot-plug inrush.

Primary references

Frequently asked questions

When does a USB-C PD design need an EPR cable?

A contract in EPR Mode requires an electronically marked EPR cable that reports EPR capability and is rated for 5 A and 50 V operation. A 5 A SPR-only cable is not an EPR cable.

Why must a USB-C PD sink start safely at 5 V?

Type-C attach starts at the safe 5 V baseline. Keep loads that require higher voltage or power disabled until the PD controller confirms the requested contract.

What is required to draw more than 3 A?

You need an explicit USB PD contract and a suitable electronically marked 5 A cable. The source, sink controller, connector, copper path, protection, and thermal design must support the current too.

Does this checker replace compliance testing?

No. It checks the capabilities you declare and the resulting first-order limits. It cannot validate protocol timing, real cable identity, transient response, controller policy, protection, thermal performance, or USB-IF compliance.

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