How many pins does a USB-C connector have?

The full receptacle has 24, in two rows of 12 (A1 to A12 and B1 to B12). Reduced receptacles exist: 16 pins for USB 2.0 only, without the SuperSpeed pairs, and 6-pin market parts for charging only (VBUS, GND, CC1, CC2).

Which resistor goes on CC1 and CC2?

For a device that draws power (sink): a 5.1 kΩ resistor from each CC pin to ground, one per pin. For a source: an Rp to the supply, whose value advertises the available current (56, 22 or 10 kΩ to 5 V for default, 1.5 A or 3 A).

Why does my USB-C charger not power my board?

Almost always because the board does not show a valid Rd on CC: resistors missing, or one resistor shared between CC1 and CC2. A compliant charger waits to see 5.1 kΩ to ground before it turns VBUS on.

What are the SBU1 and SBU2 pins for?

They are slow sideband lines (Sideband Use). USB 2.0 and USB 3 do not use them. In USB4 they carry the sideband channel (SBU1 as SBTX, SBU2 as SBRX); in DisplayPort alternate mode, the AUX channel. A simple USB 2.0 or USB 3 device leaves them unconnected.

What is the maximum voltage on USB-C VBUS?

Without negotiation, 5 V. With USB Power Delivery, the source can offer 9, 15 or 20 V, and up to 48 V in EPR mode (240 W at 5 A, introduced with USB PD 3.1). Current above 3 A needs a 5 A e-marked cable.

Pinout

USB-C pinout: all 24 receptacle pins

The USB-C connector has 24 pins in two rows, A1 to A12 and B1 to B12, arranged so the plug fits either way up. It carries VBUS power, one USB 2.0 pair, two SuperSpeed pairs in each direction, two CC configuration lines and two SBU sideband lines.

By Hugues Orgitello · Updated October 14, 2026 ·

USB-C receptacle, 24 pins

Signal names from the USB Type-C specification. TX and RX are seen from the device that carries the receptacle. The two rows are rotationally symmetric: A1 faces B12.

Receptacle seen from the front, where the plug goes in

Pin	Signal	Dir.	Description
A1	GND		Ground, current return (Ground)
A2	TX1+	Out	SuperSpeed transmit pair 1, positive (Differential pair)
A3	TX1-	Out	SuperSpeed transmit pair 1, negative (Differential pair)
A4	VBUS		Bus power: 5 V by default, up to 48 V negotiated with USB PD (Power)
A5	CC1	I/O	Configuration: attach and orientation detection, current advertisement, USB PD channel (Configuration)
A6	D+	I/O	USB 2.0, positive (tie to B6) (Differential pair)
A7	D-	I/O	USB 2.0, negative (tie to B7) (Differential pair)
A8	SBU1	I/O	Sideband Use line, for example DisplayPort AUX in alternate mode (Signal)
A9	VBUS		Bus power (Power)
A10	RX2-	In	SuperSpeed receive pair 2, negative (Differential pair)
A11	RX2+	In	SuperSpeed receive pair 2, positive (Differential pair)
A12	GND		Ground (Ground)
B1	GND		Ground (Ground)
B2	TX2+	Out	SuperSpeed transmit pair 2, positive (Differential pair)
B3	TX2-	Out	SuperSpeed transmit pair 2, negative (Differential pair)
B4	VBUS		Bus power (Power)
B5	CC2	I/O	Configuration, the other side from CC1 (Configuration)
B6	D+	I/O	USB 2.0, positive (tie to A6) (Differential pair)
B7	D-	I/O	USB 2.0, negative (tie to A7) (Differential pair)
B8	SBU2	I/O	Sideband Use line, the other side from SBU1 (Signal)
B9	VBUS		Bus power (Power)
B10	RX1-	In	SuperSpeed receive pair 1, negative (Differential pair)
B11	RX1+	In	SuperSpeed receive pair 1, positive (Differential pair)
B12	GND		Ground (Ground)

An interface to design?

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CC1 and CC2: the Rp and Rd resistors

The CC lines do three jobs: detect that a cable is attached, detect which way up, and tell the sink how much current the source can supply. The source pulls CC up through a resistor Rp; the sink pulls it down through a 5.1 kΩ resistor Rd. The resulting CC voltage advertises the available current. A source only turns VBUS on after it sees Rd.

Rp values from the Type-C specification: pulled up to 5 V, 56 kΩ advertises default USB current, 22 kΩ advertises 1.5 A and 10 kΩ advertises 3 A. Pulled up to 3.3 V, the values become 36 kΩ, 12 kΩ and 4.7 kΩ. A source may use a current source instead (80, 180 or 330 µA).

In the plug, only A5 carries CC. B5 becomes VCONN there, which powers the electronic marker (e-marker) chip. Every full-featured C to C cable (USB 3, USB4), every cable rated above 3 A and every active cable is e-marked. An e-marked cable therefore shows a resistor Ra (0.8 to 1.2 kΩ) on the unused CC pin of the receptacle.

Minimum wiring for a USB 2.0 device

A USB-C powered device that only speaks USB 2.0 needs VBUS, GND, both CC lines and both D+/D− pairs. Each CC pin gets its own 5.1 kΩ resistor to ground. A6 is tied to B6 and A7 to B7, close to the receptacle (the specification caps that bridge at 3.5 mm), so the device works whichever way the plug goes in. The SuperSpeed pairs and SBU stay unconnected.

The 16-pin receptacles sold for this job leave out exactly the SuperSpeed pairs. The 6-pin receptacles on the market only have VBUS, GND, CC1 and CC2: they are for charging only, with no data. The specification does not define them; its power-only receptacle keeps 14 contacts, with D+ and D− shorted.

The most common design mistakes

One Rd resistor shared by CC1 and CC2. The board works with most cables, then gets no power through an e-marked C to C cable, which means any USB 3, USB4 or 5 A cable: the cable’s Ra ends up in parallel with Rd, and the source no longer recognizes a sink.

No CC resistors at all. Same result: a compliant USB-C charger never turns VBUS on. Only USB-A to C cables, which contain an Rp, power the board.

D+ and D− wired on one side only. The USB link only works one way up. The A6-B6 and A7-B7 bridge makes a short stub: keep it to a few millimeters and route the pair at 90 Ω differential.

No ESD protection at the connector. The connector is where discharges come in. Put the TVS diodes as close to the receptacle as possible, with a capacitance suited to each pair’s data rate.

Frequently asked questions

FAQ

How many pins does a USB-C connector have?: The full receptacle has 24, in two rows of 12 (A1 to A12 and B1 to B12). Reduced receptacles exist: 16 pins for USB 2.0 only, without the SuperSpeed pairs, and 6-pin market parts for charging only (VBUS, GND, CC1, CC2).
Which resistor goes on CC1 and CC2?: For a device that draws power (sink): a 5.1 kΩ resistor from each CC pin to ground, one per pin. For a source: an Rp to the supply, whose value advertises the available current (56, 22 or 10 kΩ to 5 V for default, 1.5 A or 3 A).
Why does my USB-C charger not power my board?: Almost always because the board does not show a valid Rd on CC: resistors missing, or one resistor shared between CC1 and CC2. A compliant charger waits to see 5.1 kΩ to ground before it turns VBUS on.
What are the SBU1 and SBU2 pins for?: They are slow sideband lines (Sideband Use). USB 2.0 and USB 3 do not use them. In USB4 they carry the sideband channel (SBU1 as SBTX, SBU2 as SBRX); in DisplayPort alternate mode, the AUX channel. A simple USB 2.0 or USB 3 device leaves them unconnected.
What is the maximum voltage on USB-C VBUS?: Without negotiation, 5 V. With USB Power Delivery, the source can offer 9, 15 or 20 V, and up to 48 V in EPR mode (240 W at 5 A, introduced with USB PD 3.1). Current above 3 A needs a 5 A e-marked cable.

Sources

Tables built from these documents and cross-checked against manufacturer datasheets. Always check the datasheet of the connector you actually use: some manufacturers number differently.