FT232RL PCB Design Guide: Footprint, Pinout, and Alternatives

The FT232RL is the SSOP-28 member of FTDI's FT232R USB-to-UART bridge family, the chip that defined the USB-serial category for two decades. It integrates the USB 2.0 Full Speed controller, transceiver, termination resistors, 12 MHz oscillator, 3.3 V LDO, and 1024-bit configuration EEPROM into a single 28-pin package — no external crystal, no external EEPROM, and no USB-specific firmware required. The FT232RQ is the same silicon in a 32-pin QFN package; both share the same datasheet (DS_FT232R v2.16) and are collectively NRND, replaced by the FT232RNL/FT232RNQ.

The FT232RL earned its position through driver maturity. FTDI's royalty-free Virtual COM Port (VCP) and D2XX direct drivers cover Windows, macOS, and Linux with installers maintained over two decades. The chip presents a standard CDC-ACM-like interface, supports hardware (RTS/CTS, DTR/DSR) and software (XON/XOFF) handshaking, and exposes five configurable CBUS pins that can be reprogrammed as RS485 TX enable, LED drivers, clock outputs, sleep indicators, or GPIO — all through the internal EEPROM configured by FTDI's FT_PROG utility over USB. The FTDIChip-ID, a unique factory-burned serial number readable over USB, enables software licensing and security-dongle applications that no other USB-UART bridge in its class can replicate.

The main supply constraint is easy to miss: the internal oscillator requires VCC >= 4.0 V. A 3.3 V-only design therefore needs an external 12 MHz crystal or the FT232RNL replacement. VCCIO is separate and may operate from 1.8 V to 5.25 V, while the internal 3V3OUT regulator is limited to 50 mA and requires local decoupling.

What breaks boards

1. 01

   FT232RL is NRND — use FT232RNL for new designs

   FTDI's product page marks FT232RL as NRND (Not Recommended for New Designs). FTDI application note AN_560 v1.3 documents FT232RNL as the pin-compatible replacement for nearly all designs. The RN-series supports 3.3 V VCC with its internal oscillator, while FT232R requires at least 4.0 V in that mode. Use FT232RNL for a new layout unless a documented compatibility constraint requires the older part.

2. 02

   VCC must be >=4.0 V with internal oscillator — 3.3 V designs need an external crystal

   The FT232R datasheet Table 5.2 specifies VCC min = 4.0 V when using the internal clock generator. If you power the FT232RL from a 3.3 V rail and use the internal oscillator, the device is out of spec and may not enumerate reliably. For 3.3 V-only designs, either add an external 12 MHz crystal (OSCI/OSCO pins, see FTDI application note AN_100) or switch to the FT232RNL which supports 3.3 V VCC with internal oscillator. This is the single most common FT232R design mistake: copying a 5 V reference schematic, substituting a 3.3 V supply, and getting a board that enumerates on some USB ports but not others.

3. 03

   3V3OUT is a 50 mA regulator output, not a general-purpose 3.3 V rail

   The internal regulator output is specified at 3.3 V typical with 50 mA maximum output current. FTDI's reference circuits place a 100 nF capacitor close to 3V3OUT. Use it for the FT232R's USB-transceiver supply and only light external loads within the current budget. Power the UART-side logic level through VCCIO from the intended I/O rail rather than assuming 3V3OUT can supply the rest of the board.

4. 04

   The TX/RX buffer sizes are relative to the USB interface — not the UART side

   The FT232R datasheet lists a 128-byte RX buffer and a 256-byte TX buffer, but note the perspective: RX is data arriving from the USB host (destined for the UART TXD pin), and TX is data arriving from the UART RXD pin (destined for the USB host). This is the reverse of what a UART-centric datasheet would label them. The buffers are fixed sizes — unlike the CP2102N with its 512-byte FIFOs in both directions, the FT232R's smaller buffers mean hardware flow control (RTS/CTS) matters sooner at high baud rates. Buffer smoothing technology helps with throughput, but at 3 Mbaud the 128-byte RX buffer fills in roughly 340 us.

5. 05

   CBUS pin configuration is burned into EEPROM — not strapped with resistors

   The five CBUS pins (CBUS0–CBUS4) are configured entirely through the internal EEPROM using FTDI's FT_PROG utility over USB — there are no external configuration resistors. Factory defaults: CBUS0 = TXLED#, CBUS1 = RXLED#, CBUS2 = TXDEN, CBUS3 = PWREN#, CBUS4 = SLEEP#. PWREN# requires an external 10 kohm pull-up resistor. If you need different CBUS functions (clock outputs, GPIO, bit-bang strobes), you must program the EEPROM in-circuit before the board ships. This means every FT232RL board needs an EEPROM programming step in production unless the factory defaults match the design exactly. The EEPROM is rated for 10,000 write cycles — fine for production programming but not for runtime reconfiguration.

Key specifications

Verified against the manufacturer datasheet on 2026-07-12. Confirm the current revision before production use.

Alternatives

• FT232RNL: FTDI's direct pin-compatible replacement for FT232RL in the same SSOP-28 package. Key improvement: supports internal oscillator at 3.3 V VCC (FT232R needs >=4.0 V). Drop-in for nearly 100% of designs per AN_560 v1.3. This should be your first choice for a new FT232-class design.
• CP2102N: Silicon Labs USB-UART bridge with 3 Mbaud, internal oscillator, configurable GPIOs, and larger 512-byte FIFOs. QFN packages from 3x3 mm. Solid driver support across OSes. Different package/pinout — not a drop-in replacement for FT232RL.
• CH340C: WCH low-cost USB-UART bridge with internal oscillator, SOP-16. Max 2 Mbaud. Dominant on budget dev boards. Requires driver install on most platforms. Different pinout.
• FT231XQ: FTDI's newer single-supply USB-UART in QFN-20 (4x4 mm). Full Speed USB, 3 Mbaud, internal oscillator, CBUS pins. Single 3.3 V supply. Recommended by FTDI for new cost-sensitive designs alongside FT232RN.

Common questions

FT232RL vs FT232RQ — what is the difference?

Same silicon die, different package. FT232RL is 28-pin SSOP with 1.27 mm pitch — the classic through-hole-friendly SMD package. FT232RQ is 32-pin QFN (5x5 mm) with an exposed center pad that must be soldered for proper thermal performance (thetaJA 62.31 degC/W unsoldered vs 31.49 degC/W when soldered with 9 vias to a plane). Both share the same datasheet, same electrical specs, and the same NRND lifecycle status. Pin counts differ because the QFN has 4 additional NC (no-connect) pins. Choose FT232RL for hand-solderability; choose FT232RQ for compact automated assembly.

Should I use FT232RL or FT232RNL for a new design?

Use FT232RNL. FTDI explicitly marks FT232RL as NRND. AN_560 v1.3 documents FT232RNL as the pin-compatible replacement — your FT232RL layout accepts FT232RNL without changes. The RN-series fixes the most common FT232R design problem: VCC can now be 3.3 V with the internal oscillator (FT232R requires >=4.0 V). There is no engineering reason to start a new design with FT232RL in 2026.

How do I tell if my FT232RL is genuine or counterfeit?

Buy through FTDI or an authorized distributor and retain normal lot traceability. The chip exposes an FTDIChip-ID that software can read, but this page does not treat markings, price, or one identifier check as proof of authenticity. If provenance matters, control the supply chain rather than relying on visual inspection.

Does the FT232RL need drivers?

On Windows, yes — FTDI's VCP driver must be installed. The driver is WHQL-certified and available through Windows Update on recent versions. On macOS 10.9 and later, Apple's built-in AppleUSBFTDI driver handles enumeration without additional installation. On Linux, the ftdi_sio kernel module has been mainline since kernel 2.4 and loads automatically. FTDI also provides D2XX direct drivers for applications that need a DLL/SO API rather than a virtual COM port. All drivers are free downloads from ftdichip.com/drivers/.

Can I power the FT232RL from a 3.3 V rail?

Only if you add an external 12 MHz crystal (or external oscillator) on the OSCI/OSCO pins. The internal oscillator requires VCC >= 4.0 V per Table 5.2. With an external crystal, VCC can be as low as 3.3 V. The VCCIO pin can independently be set anywhere from 1.8 V to 5.25 V regardless of VCC, allowing the UART side to match a 1.8 V, 2.5 V, or 3.3 V microcontroller while the USB side runs from 5 V VBUS. If your design is 3.3 V-only and you cannot add a crystal, switch to FT232RNL which supports internal oscillator at 3.3 V VCC.

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