USB-to-UART selection involves more than baud rate. Handshaking signals, I/O voltage, package, driver support, configuration, and RS-485 direction control all affect PCB layout, software integration, and maintenance.

FTDI’s FT230XS-R and FT231XS-R and Silicon Labs’ CP2102N-A02-GQFN28R integrate a USB 2.0 full-speed controller, USB transceiver, and on-chip clock generation, so no external crystal is required. All support 300 baud to 3 Mbaud and handle the USB protocol on-chip. Key differences are control signals, I/O architecture, auxiliary functions, package, and software tools.

Using the lower-pin-count FT230XS-R as the baseline, this guide highlights practical selection criteria for new designs, upgrades, and cross-vendor replacements.

Key Specification Comparison

Application Fit

• FT230XS-R

Best suited for: Compact MCU debug ports, sensor interfaces, data loggers, and serial adapters requiring basic USB-to-UART connectivity and an SSOP package.

Design insight: The FT230XS-R provides TXD, RXD, RTS#, and CTS#. Its 16-pin package simplifies routing and connector design. It is the most direct choice when DTR, DSR, DCD, and RI are not needed, but future modem-control requirements should be considered.

• FT231XS-R

Best suited for: Industrial instruments, external RS-232 transceiver interfaces, and serial converters requiring full handshaking while retaining FTDI VCP/D2XX drivers and FT_PROG.

Design insight: The FT231XS-R shares the FT-X platform and driver ecosystem of the FT230XS-R, while adding DTR#, DSR#, DCD#, and RI#. It expands UART control without changing software platforms, but its SSOP-20 package requires more routing.

• CP2102N-A02-GQFN28R

Best suited for: New 3.3 V I/O designs requiring full handshaking, additional GPIOs, remote wakeup, or configurable RS-485 direction control.

Design insight: The QFN-28 device offers up to seven GPIOs, some of which can be configured for TX/RX activity indication, RS-485 direction control, and WAKEUP. The clock-output function is multiplexed with the RI pin. It suits Silicon Labs VCP/USBXpress platforms, but is not a drop-in FTDI replacement because its power architecture, package, pinout, USB configuration, and drivers differ.

Design Considerations

• Handshaking and System Resources

Use the FT230XS-R when TX/RX and RTS/CTS are sufficient. Designs requiring DTR, DSR, DCD, or RI should consider the FT231XS-R or CP2102N-A02-GQFN28R.

Additional control signals improve compatibility with some equipment and software, but consume more connector contacts and PCB routing.

All three support up to 3 Mbaud. Actual throughput and latency also depend on USB host scheduling, drivers, packet size, buffering, and the operating system, so performance-sensitive designs should be tested in the target system.

• Power and Logic Levels

The FT230XS-R and FT231XS-R use a 2.97-5.5 V main supply and provide VCCIO for 1.8 V, 2.5 V, or 3.3 V logic. Their UART and CBUS inputs are 5 V tolerant, but output levels follow VCCIO; this is not full bidirectional 5 V compatibility.

The CP2102N-A02-GQFN28R has no separate VIO pin, so digital I/O follows VDD at 3.0-3.6 V. Applying 5 V to VREGIN does not create 5 V I/O. Check input thresholds and absolute-maximum ratings before deciding whether level shifting is required.

• Drivers, Configuration, and Production Programming

The FT230XS-R and FT231XS-R use FTDI VCP/D2XX drivers and FT_PROG for USB descriptors, serial numbers, and CBUS functions. Migration within the FT-X family is relatively simple, but pin functions, defaults, and production files still require review.

The CP2102N-A02-GQFN28R uses Silicon Labs VCP/USBXpress drivers, and Xpress Configurator programs its internal ROM. Cross-vendor migration should verify driver deployment, COM-port enumeration, VID/PID and serial-number settings, suspend and wakeup behavior, and production programming.

Product Summary

WIN SOURCE supplies FTDI and Silicon Labs USB interface devices, including these three models. Before approving a substitute, confirm inventory and lead time, then validate package, pinout, I/O voltage, drivers, and production configuration. Visit WIN SOURCE to check availability and request a quote.