## Overview of the FT231XS-R The **FT231XS-R** is a compact, cost-effective **USB to Full Handshake UART** interface integrated circuit (IC) developed by FTDI Chip. It belongs to the X-Chip series, designed to reduce component count and PCB space by integrating many external functions. --- ### 1. Key Technical Specifications The table below highlights the primary electrical and physical characteristics: | Feature | Specification | | :--- | :--- | | **Interface** | USB 2.0 Full Speed (12Mbps) | | **Data Rate** | 300 baud to 3 Mbaud | | **Operating Voltage** | 3.3V to 5.25V | | **I/O Voltage** | 1.8V to 3.3V (VCCIO) | | **Package** | 20-pin SSOP (Shrink Small Outline Package) | | **Operating Temp** | -40°C to +85°C | | **Internal Clock** | Fully integrated (No external crystal required) | | **MTP Memory** | 2048 Bytes (For storing USB descriptors/strings) | --- ### 2. Internal Electronic Components The FT231X series is known for its high level of integration, which simplifies the surrounding circuit design. * **Integrated Clock Circuit:** Unlike older USB-UART chips, it does not require an external crystal or resonator, saving space and cost. * **Integrated LDO Regulator:** It features a 3.3V Low Dropout regulator to power the USB transceiver and internal logic. * **MTP (Multi-Time Programmable) Memory:** Used to store the USB Vendor ID (VID), Product ID (PID), and device strings. This can be programmed in-circuit via USB. * **Battery Charger Detection:** A unique feature that detects the presence of a USB charging port, allowing for higher current charging (up to 1.8A) if connected to a dedicated charger. --- ### 3. Pinout Functions The 20-pin SSOP package is organized to handle both the USB physical layer and the UART signaling. | Pin Type | Examples | Description | | :--- | :--- | :--- | | **USB Signals** | USBDP, USBDM | Differential pair for USB data communication. | | **UART Signals** | TXD, RXD, RTS, CTS | Standard asynchronous serial data and flow control. | | **Handshaking** | DTR, DSR, DCD, RI | Full modem control signals. | | **CBUS Pins** | CBUS0 - CBUS3 | Configurable I/O pins for LED indicators or clock output. | | **Power** | VCC, VCCIO, GND | Supply voltage and I/O interface voltage level setting. | --- ### 4. Typical Application Circuit To use the FT231XS-R, very few external components are needed: 1. **Decoupling Capacitors:** Usually 0.1uF and 4.7uF on the VCC pins. 2. **USB Connector:** Standard Type-B, Mini-B, or Micro-B. 3. **Resistors:** 27 Ohm resistors are sometimes placed on USBDP/USBDM lines for impedance matching, though the chip integrates many of these protections. ```text [USB Port] <---> [FT231XS-R] <---> [Microcontroller UART] | [MTP Memory] (Internal) ```