Concept renderUSB-C power delivery lets a device negotiate more than 5 V over the CC wire, up to 48 V and 240 W under the current USB PD revision. Most small battery devices do not need it. Two 5.1 kΩ pull-down resistors on CC1 and CC2 give a clean 5 V sink, which covers single-cell chargers in wearables and trackers.
A USB-C port on a small device looks simple, and it is where many charging bugs start. This guide is for the founder or engineering lead who decides whether a device needs USB power delivery or a plain 5 V sink. It covers the CC resistors, PD negotiation, protection, compatibility testing and USB-IF certification.
This is an engineering summary. Specifications, part data and fees change, so check the linked pages. All sources were read on November 12, 2026. The parts named are examples, not recommendations.
What is USB-C power delivery, and how does it differ from plain USB-C?
USB Type-C is the connector and cable. It also defines a configuration channel (CC), a wire that detects attachment and sets up power. USB Power Delivery (USB PD) is a protocol on that CC wire that lets a charger and a device agree on more than the 5 V default.
TI lists what the CC channel does: detect attachment, resolve cable orientation, set source and sink roles, and configure power through USB Type-C current modes or USB PD (TI SLVSE24C, as of November 2026). A source asserts a pull-up (Rp) on CC. A sink asserts a pull-down (Rd).
USB-IF says USB PD Revision 3.1 delivers up to 240 W over a full-featured USB Type-C cable. Before it, USB PD was limited to 100 W, using 20 V and cables rated at 5 A. New 28 V, 36 V and 48 V fixed voltages enable up to 140 W, 180 W and 240 W (usb.org USB Power Delivery, as of November 2026).
Does a small battery device need USB PD at all?
Usually not. The battery charger sets the ceiling, and 5 V often covers it.
- TI's BQ25120A, a charger and power management IC for wearables, supports charge currents from 5 mA to 300 mA (datasheet SLUSD08A, as of November 2026).
- Nordic's nPM1300 PMIC lists a charge current of 32 to 800 mA, a USB Type-C compliant system regulator with 100 mA, 500 mA and 1500 mA current limits, an input voltage of 4.0 to 5.5 V and 22 V overvoltage protection (nPM1300 product page, as of November 2026).
Both are 5 V input designs. A ring, band or tracker with one small Li-ion cell charges well inside those limits. USB PD would add a controller, a wider voltage range on VBUS and more tests, for no gain in charge time.
The 5 V sink with two Rd resistors
The minimum USB-C sink is two resistors. TI describes the attach model this way: a sink advertises Rd on both its CC pins, and the source monitors both CC pins for a voltage lower than its unterminated voltage (TI SLVSE24C, as of November 2026). TI gives the pull-down termination as Rd 5.1 kΩ (TI SLVSFP1, as of November 2026).
Put one resistor on CC1 and one on CC2. The source uses them to see that a device is attached and which way the plug is turned, so a port with no Rd may get no power from a C-to-C cable. Two common bugs: one shared resistor for both CC pins, and no Rd at all because the device charged fine from a USB-A cable on the bench.
For the regulator after VBUS, see LDO vs buck converter. For the battery side, see battery management systems for small devices.
Which charging input fits which device?
The table compares four ways to take power from USB-C. The rows are engineering reasoning, and none describes a specific project.
| Option | How it works | Where it fits | Watch out for |
|---|---|---|---|
| 5 V sink with two Rd resistors | Two pull-down resistors on CC1 and CC2. The device takes 5 V. | Rings, bands, pendants and trackers with one small cell. | The charger must handle hot plug and cheap adapters. |
| PD sink controller, fixed voltages | A controller talks USB PD on the CC wire and asks the charger for 9, 12, 15 or 20 V. | Speakers, handheld devices with bigger packs, products with a two-cell or larger battery. | Every part on VBUS must survive the highest voltage the device can request. |
| PD sink with PPS | The sink asks for an adjustable voltage and a current limit, and can change the request while charging. | Fast direct charging of a larger battery where the charger stage should waste less heat. | More firmware and test cases, and not every PD charger offers PPS, so check the chargers your users own. |
| PD with EPR (28, 36 or 48 V) | Extended Power Range adds higher fixed voltages and adjustable voltage above 15 V. | Rarely a small device. Laptops, docks, tools and larger equipment. | Needs EPR-capable cables and chargers, and parts rated for the higher voltage. |
Wireless charging is another option for sealed wearables. Qi wireless charging for wearables compares it with a wired port.
How does USB PD negotiation work in a sink?
After attach, the charger sends its source capabilities: a list of power data objects (PDOs), each a voltage and a maximum current. The sink requests one, and the charger switches VBUS. If the sink asks for nothing, VBUS stays at 5 V.
A sink controller with no firmware
Some PD sink controllers need no code. TI says its TPS25730, a stand-alone sink-only USB Type-C and PD controller, is configured through resistor pin strapping with no external EEPROM, microcontroller or firmware. It is PD3.1 compatible for sink-only applications (TPS25730 datasheet SLVSGP9, as of November 2026).
Its strap pins set a minimum voltage of 5 to 20 V, a maximum of 9 to 20 V, and a maximum current of 1.5 to 5 A. When the charger cannot meet that range, the controller sets a Capabilities Mismatch bit (SLVSGP9, as of November 2026). Decide what the product does then: charge slowly at 5 V, light an LED, or refuse to charge.
PPS, AVS and Extended Power Range
Newer controllers add adjustable voltages. TI lists the TPS26750 as supporting PPS source and sink, and EPR source and sink with 28 V, 36 V, 48 V and AVS (TPS26750 product page, as of November 2026). The same page states that PD3.1 silicon is required for certification of new USB PD designs. If you plan to certify, check the PD revision of the controller before you pick it.
For a small device, EPR is almost never the answer. A part that can request 48 V puts 48 V on your VBUS net.
What protection do VBUS and the CC pins need?
The USB-C port is the one place where the outside world touches your circuit with power. Plan for overvoltage, reverse current, inrush and ESD.
- Voltage ratings. The TPS25730 lists absolute maximum ratings of 28 V on VBUS and 26 V on CC1 and CC2. TI recommends a TVS diode with a breakdown voltage between the recommended maximum and the absolute maximum, and names the TVS2200 as an example (SLVSGP9, as of November 2026).
- CC shorts. A faulty cable or charger can put VBUS on CC. TI describes the TPS26750 as having 26 V tolerant CC pins for protection when connected to non-compliant devices (product page, as of November 2026).
- Overvoltage and reverse current. The TPS25730 sink path includes both protections (SLVSGP9). The nPM1300 lists 22 V overvoltage protection on its input (product page). Both as of November 2026.
- Inrush. The TPS25730 uses a slew rate control loop so its sink switches do not turn on too quickly (SLVSGP9, as of November 2026). Keep bulk capacitance on VBUS within the allowed limit.
- ESD. Place TVS parts at the connector, with a short path to ground. See ESD testing to IEC 61000-4-2 for how the test is run.
The dead battery case
A device with a flat battery must still present Rd, or a compliant charger will not turn on VBUS. Plain resistors do this by nature. The TPS25730 integrates a dead battery Rd and a 3.3 V LDO powered from VBUS for this case (SLVSGP9, as of November 2026). Test it with a fully drained battery.
How should you test chargers and cables?
Compatibility problems show up in the field, from chargers and cables you never tried. Run this list at every prototype build.
- Charge from at least one charger of each kind you expect: a plain 5 V Type-C charger, a PD charger, a laptop port and a legacy USB-A charger with an A-to-C cable.
- Plug and unplug under load hundreds of times, at both cable orientations, and watch VBUS and the system rail on a scope for overshoot and resets.
- Start from a fully discharged battery (dead battery case) and confirm the device boots and charges without user action.
- Ask a PD charger for each voltage your design can request, then pull the cable mid-charge and confirm the device falls back to 5 V or stops cleanly.
- Zap the connector shell and pins per your ESD plan, then confirm the CC and VBUS paths still work.
What do USB-IF certification and the USB logos involve?
USB-IF's compliance page says there are five avenues for certifying a product, that certified products must use USB-IF certified connectors, and that they are added to the Integrators List. To use the certified USB logos, a company needs a valid USB-IF Trademark License Agreement on file and a certified product. Vendors and test labs negotiate test prices between them (usb.org compliance, as of November 2026).
USB-IF's vendor ID page lists the fees it charges, as of November 2026 (usb.org getting a vendor ID):
- Membership is $5,000 per year and includes a vendor ID if one has not already been assigned.
- A logo license is $3,500 for a two-year term, and the fee is waived for members. A licensee must also buy a vendor ID if it has none.
- A vendor ID on its own is $6,000.
Test lab fees come on top and are quoted by the lab. A charge-only device still needs a decision on certification and logo use. This is an engineering summary and not legal advice.
What should you ask your hardware team about the USB-C port?
Bring these questions to the schematic review, before the board is laid out.
- What is the most power the device needs while charging and running at the same time, at the lowest battery voltage?
- If we use PD, which voltages and currents does the sink request, and what happens when a charger offers none of them?
- What is the highest voltage that can reach VBUS, and is every part on VBUS and CC rated above it with margin?
- Do we plan USB-IF certification or the USB logos, and who holds the vendor ID?
- Which chargers and cables are on the compatibility test list, and who keeps it current?
The charging input is part of the electronics work. For how that work is organized across gates, see engineering.
Questions about USB-C power delivery
Can I just put two 5.1 kΩ resistors on CC1 and CC2?
For a 5 V device, yes. A sink advertises Rd on both CC pins, and TI gives Rd as 5.1 kΩ (TI SLVSFP1, as of November 2026). Each CC pin needs its own resistor. TI describes a sink as exposing independent Rd terminations on CC1 and CC2. If one resistor is shared, the two pins are tied together, and with some e-marked cables the charger can misread the attach and supply no power. That last point is engineering reasoning, not a TI statement. You still need protection on VBUS and a charger that handles hot plug.
Does USB PD charge a small battery faster?
Only if the charger stage can use the extra power. A single-cell wearable charger such as the BQ25120A supports charge currents from 5 mA to 300 mA (datasheet SLUSD08A, as of November 2026), which 5 V covers with room to spare. PD helps when the battery and charger accept more power than 5 V can carry.
Do I need USB-IF certification to sell a USB-C device?
This is an engineering summary and not legal advice. USB-IF ties logo use to certification. Its compliance page says companies that want to use the logos must have a valid trademark license agreement on file and the product must be certified (usb.org, as of November 2026). Ask counsel how this applies to your product and packaging.
How can Duobay help with USB-C charging in my device?
Duobay develops custom devices with a Shenzhen engineering team that covers electrical, firmware, mechanical, app and test work. The charging input is part of the electronics design, and we build samples and small batches. Firmware source and the SBOM are delivered to you, and source files are assigned to you at every paid gate. Initial calls are free. Tell us about your device.
If you want the USB-C input of your device reviewed against your battery, enclosure and charger list, tell us about your device.
Sources. All pages accessed November 12, 2026. Vendors revise datasheets and USB-IF updates its pages, so confirm current values before you decide.
- USB-IF, USB Charger (USB Power Delivery) (link)
- USB-IF, Compliance (link)
- USB-IF, Getting a Vendor ID (link)
- Texas Instruments, TPS25868-Q1 and TPS25869-Q1 datasheet SLVSFP1, Detecting a Connection (link)
- Texas Instruments, TPS25820 and TPS25821 datasheet SLVSE24C (revised August 2019) (link)
- Texas Instruments, TPS25730 datasheet SLVSGP9 (October 2023) (link)
- Texas Instruments, TPS26750 product page (link)
- Texas Instruments, bq25120A datasheet SLUSD08A (link)
- Nordic Semiconductor, nPM1300 product page (link)
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