Spark Logic

CP2102 USB-to-UART bridge connection guide

CP2102 USB-to-UART bridge QFN-28 wiring guide with power, signal assignments, and bench checks.

QFN-28

29 contacts Current package

Silicon Labs · 5 × 5 mm · 0.50 mm pitch · grounded exposed pad

Connect the bus-powered USB bridge

Required

Feed REGIN and VBUS from the connector’s VBUS. Bypass REGIN and VDD at the package. Ground the exposed pad with the GND lead. Follow the manufacturer’s USB ESD and layout guidance.

1 µF in parallel with 100 nF between USB supply and ReturnUSB supply1 µF in parallel with 100 nFReturn
4.7 µF in parallel with 100 nF between 3.3 V output and Return3.3 V output4.7 µF in parallel with 100 nFReturn

Bench checks

  • Check for around 3.3 V on VDD after connecting USB.
  • Verify enumeration before connecting any external UART circuit.

Silicon Labs CP2102/9 datasheet, Rev. 1.8, Fig. 5, Fig. 6 and Table 9.

Connection scenarios

Test the UART in loopback

Unplug USB and jumper the bridge transmit output to its own receive input. Plug USB back in, open the enumerated port and disable local echo and flow control.

Bench checks

  • Send a short string at 9,600 bit/s, 8 data bits, no parity and 1 stop bit. The received bytes should match the transmitted bytes.
  • Remove the jumper before connecting another UART. Cross the two data lines, share ground and check the logic levels first.

Silicon Labs CP2102/9 datasheet, Rev. 1.8, UART signal descriptions. Loopback is a bench test.

QFN-28 wiring map

Highlighted contacts are used in the required step or selected circuit. Select a contact to inspect it.

QFN-28
Top view. Match pin 1 to the package mark. The numbers advance counterclockwise. Scroll the map to reach all contacts.
Selected pin details

20 · NC

Unconnected · NC / reserved

Leave open for this circuit.

Silicon Labs CP2102/9 datasheet, Rev. 1.8, Table 9 and Fig. 2

Electrical limits · Pin in the reference

Models and documents

This map covers the original CP2102 in QFN-28. The CP2102N uses a different datasheet and package map. Pin 18 is reserved on the CP2102 and is VPP on CP2109.

CP2102-GM
5 × 5 mm · 0.50 mm pitch · grounded exposed pad