The charging source, magnetic connector, cable and device electronics must agree on how power is supplied. The data path must also remain reliable while the charging current is flowing.
What can four contacts carry?
A straightforward USB 2.0 arrangement uses one contact each for VBUS, ground, D+ and D−. This can allow a device to charge while exchanging data with a host. It is a useful layout for a compact dock or handheld terminal when those four connections satisfy the product's electrical requirements.
"Fast charging" needs a more precise definition. A connector capable of carrying a given current does not cause a charger to deliver it. The source must offer the required power, the device must request or accept it using a compatible method, and the contacts and cable must carry it without excessive voltage drop or heating.
Some charging schemes use the USB data lines for detection or negotiation. That may affect how data communication operates during charging. The exact behavior has to be checked against the chosen charging method rather than inferred from the presence of D+ and D−.
What does a fifth contact add?
A fifth pogo contact gives the designer another electrical path. It might be used for device identification, connection detection, a dedicated control line or another function required by the equipment. Its assignment must be defined by the circuit on both sides of the magnetic connection.
The extra contact does not, by itself, provide USB Power Delivery (USB PD). In a USB-C system, the Configuration Channel, or CC, has a role in connection detection and power negotiation. USB 2.0 data uses D+ and D−; those lines are not substitutes for CC. A design that passes USB-C functions through a magnetic interface needs its complete connector and control architecture reviewed, including plug orientation and what happens when the magnetic halves separate.
A USB-C plug on one end of a cable therefore does not establish that the pogo end supports USB PD. Nor should a proprietary magnetic interface be described as USB certified merely because it connects to a USB port.
| Intended function at the magnetic interface | Four contacts | Five contacts |
|---|---|---|
| Power and ground | Possible | Possible |
| USB 2.0 D+ and D− alongside power | Possible with an appropriate design | Possible with an appropriate design |
| An additional independent signal | Requires a different assignment or architecture | One more contact is available |
| USB-C PD negotiation | Cannot be assumed from pin count | Cannot be assumed from pin count |
| Higher charging power | Depends on the complete system | Depends on the complete system |
The cable and contacts must carry the load
At higher current, small resistances become significant. Voltage drop can reduce the power reaching the device, while heat builds up at the pin-to-pad interface, inside the pogo pin, at the termination and along the cable. The intended current must be evaluated as a continuous operating condition where the product calls for it, not just as a brief peak.
Pin size alone is an incomplete rating. The pogo pin's internal current path, working compression, mating pad finish and contact force all affect resistance. Cable conductor size and length matter as well. If multiple contacts are assigned to power or ground, their currents should not be assumed to divide equally without checking the assembled design.
The magnetic parts must position the contacts accurately and hold them at the intended working height. A strong magnet cannot correct a pin that misses its pad or reaches the end of its travel. Because the interface is detachable, the circuit should also be assessed for exposed contacts, accidental shorts and repeated connection while power is available.
Data transfer needs its own checks
For USB 2.0 data, D+ and D− must be mapped correctly through the cable and both connector halves. Their routing, the transitions through the pogo contacts and the return path affect signal quality. Cable length and construction can become more important as the required data rate rises.
Testing should reflect normal use: transfer data while charging at the intended power, move the cable within its expected range, and repeat the connection after mating cycles. Watch for failed device detection, transfer errors and momentary disconnects. Passing a continuity test at the workbench is insufficient evidence of stable communication in the finished product.
When developing a custom 4-pin or 5-pin magnetic cable, we can work from the customer's connector and PCB drawings to define the contact layout, pogo pin structure, cable termination and mating geometry as one solution. The input connector type, charging method and required data function should be specified before the pin assignment is fixed.
FAQ
Can a 4-pin magnetic pogo cable charge and transfer USB 2.0 data simultaneously?
Yes. VBUS, ground, D+ and D− can occupy the four contacts, provided the complete cable and device design supports the intended charging and data behavior.
Is a 5-pin pogo cable automatically compatible with USB-C PD?
No. USB-C PD depends on the appropriate CC connection and compatible control circuitry. The fifth contact has no inherent PD function; its use depends on the circuit design.
Does adding a fifth pin make charging faster?
No. Charging power depends on the source, negotiation method, device charging circuit, cable and contact ratings. An extra pin may be useful for a required signal, but it is not a power rating.
What information is needed to design a custom charging and data cable?
Provide the connector drawings, USB-A or USB-C input configuration, intended charging voltage and current, charging protocol, data standard and cable length. The device-side PCB layout and expected mating conditions are needed to verify the magnetic interface.
