MCP2221-I/ST - USB 2.0 to I2C/UART Bridge with GPIO | Microchip
MPN: MCP2221-I/ST ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $2.87 | $2.87 |
| 10 | $2.58 | $25.80 |
| 100 | $2.3 | $230.00 |
| 500 | $2.05 | $1,025.00 |
| 1,000 | $1.8 | $1,800.00 |
MCP2221-I/ST Overview
A USB bridge IC is a category of interface controller that converts between USB and a slower peripheral bus (UART, I2C, SPI). The device sits downstream of the USB PHY and upstream of the application processor or sensor cluster, presenting a HID-class or vendor-class interface to the host OS so that no custom driver is required on Windows, macOS, or Linux. Within the broader taxonomy, an interface bridge belongs to the Interface ICs family of integrated circuits, alongside I/O expanders, UART transceivers, and USB controllers.
The MCP2221-I/ST highlights 12 Mbps USB full-speed, a programmable I2C controller that supports Standard-mode (100 kHz), Fast-mode (400 kHz), and Fast-mode Plus (1 MHz), a UART supporting 300 to 115200 baud, 64-byte transmit and receive FIFO buffers, and 4 GPIOs that can be individually mapped to dedicated digital functions. A factory-programmed USB VID/PID and the Microchip HID-based configuration DLL allow the device to enumerate as a standard HID, requiring no driver install on modern hosts.
Typical applications include USB-to-I2C sensor dongles, USB-to-UART debug bridges that replace legacy RS-232 ports, HID-based EEPROM/flash programming fixtures, breadboard prototyping platforms (Arduino-style native-USB boards), industrial configuration and diagnostic ports, and PC-side emulators for I2C peripheral evaluation. The TSSOP-14 footprint is friendly to hand-soldering, which is why the part remains popular in hobbyist and low-volume production designs.
When designing with this device, observe USB-IF bus-layout rules: keep the D+/D- traces length-matched within 2 mm, place the VBUS decoupling capacitor within 3 mm of the VBUS pin, and provide a 1 uF bulk capacitor on the internal 3.3V LDO output. Avoid routing the I2C lines through noisy switching-regulator regions because the internal pull-ups are weak and intended only for low-speed evaluation.
This page synthesizes current distributor stock, parametric drop-in alternatives, and practical PCB-layout notes drawn from the Microchip datasheet, providing information not found in any single distributor product listing.
Drop-in alternatives for MCP2221-I/ST — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
MCP2221A-I/ST
✅ Drop-In📋 Reference alternative (not in catalog)
MCP2221AT-I/ST
✅ Drop-In📋 Reference alternative (not in catalog)
MCP2221-I/ST Specifications
| Function | USB 2.0 to I2C/UART protocol converter with GPIO |
| USB Speed | Full-Speed (12 Mbps) |
| USB Compliance | USB 2.0 Full-Speed |
| Downstream Interfaces | I2C/SMBus, UART |
| I2C Modes | Standard 100 kHz, Fast 400 kHz, Fast-Plus 1 MHz |
| UART Baud Rates | 300 to 115200 baud |
| FIFO Buffers | 64-byte TX and 64-byte RX |
| GPIO Count | 4 (multiplexed with dedicated digital functions) |
| Supply Voltage (VBUS) | 3.0 V to 5.5 V |
| Internal LDO | 3.3 V for core logic |
| Operating Temperature | -40 C to +85 C (Industrial grade, 'I' suffix) |
| Package | 14-pin TSSOP (4.4 mm body width, ST suffix) |
| Mounting Type | Surface Mount |
| MSL Level | 1 (per Microchip packaging profile) |
| RoHS Status | Compliant |
| Lead-Free | Yes |
| External Crystal | Not required (internal oscillator) |
MCP2221-I/ST Pin Configuration
| Pin 1 | VBUS — USB bus power input, 3.0 V to 5.5 V |
| Pin 2 | VDD33 — Internal 3.3V LDO output, decouple with 1 uF |
| Pin 3 | VSS — Ground |
| Pin 4 | GP3 — General-purpose I/O 3 / dedicated function |
| Pin 5 | GP2 — General-purpose I/O 2 / dedicated function |
| Pin 6 | GP1 — General-purpose I/O 1 / dedicated function |
| Pin 7 | GP0 — General-purpose I/O 0 / dedicated function |
| Pin 8 | D- — USB data minus |
| Pin 9 | D+ — USB data plus |
| Pin 10 | URX — UART receive |
| Pin 11 | SCL — I2C clock |
| Pin 12 | SDA — I2C data |
| Pin 13 | UTX — UART transmit |
| Pin 14 | SSPL — External signal / clock output |
Typical Applications
MCP2221-I/ST is suitable for 6 applications: USB-to-I2C Sensor Dongle, USB-to-UART Debug Bridge, HID-Based EEPROM/Flash Programming Fixture, Breadboard Prototyping Platform, Industrial Configuration and Diagnostic Port, PC-Side I2C Peripheral Evaluation.
USB-to-I2C Sensor Dongle
The MCP2221-I/ST is a natural fit for a USB-to-I2C sensor dongle because its integrated USB 2.0 full-speed transceiver, hardware I2C controller, and 4 GPIOs are all that a typical PC-attached sensor bridge requires. The part supports Standard-mode (100 kHz), Fast-mode (400 kHz), and Fast-mode Plus (1 MHz), which covers virtually every I2C sensor on the market from simple temperature chips to higher-speed ADCs. Placed between the USB VBUS pin and the downstream sensor I2C bus, the MCP2221 enumerates as a standard HID device, so no custom driver install is required on Windows, macOS, or Linux. Unlike a generic USB-UART bridge, the MCP2221 provides hardware clock stretching and multi-master support, allowing multiple sensors on the same bus without software arbitration.
Recommended
USB-to-UART Debug Bridge
The MCP2221-I/ST serves as a USB-to-UART debug bridge that replaces legacy RS-232 ports and FTDI cables in low-cost debug setups. Its UART supports 300 to 115200 baud with 64-byte TX and RX FIFOs, which covers the most common firmware debug speeds used by 8-bit and 32-bit MCUs. The TSSOP-14 package fits on a small adapter PCB alongside a USB-C connector, and the integrated LDO removes the need for an external 3.3V regulator. Unlike the FT232, the MCP2221 also exposes 4 GPIOs that can be used for reset, bootloader, or LED control during firmware flashing.
Recommended
HID-Based EEPROM/Flash Programming Fixture
The MCP2221-I/ST is well suited for a HID-based EEPROM or flash programming fixture because the part presents a standard HID interface that does not require custom driver installation on production-line PCs. The I2C controller handles the byte-level writes needed to program 24-series EEPROMs and SPI-to-I2C bridge-attached flash chips at up to 1 MHz. The 4 GPIOs can be assigned to chip-select, write-protect, and status-LED functions, replacing an external MCU in the fixture. According to Microchip datasheet examples, the HID DLL provides write and read functions at the system level, allowing fixture software to be written in any high-level language.
Recommended
Breadboard Prototyping Platform
The MCP2221-I/ST is widely used on breadboard prototyping platforms because the TSSOP-14 footprint can be adapted to a 0.1-inch header breakout board, and the HID driver means no special host setup is required. Designers use it to add native-USB connectivity to Raspberry Pi Pico clones, Arduino-style boards, and custom 8-bit sensor nodes. The 4 GPIOs can be repurposed as button inputs or status LEDs, and the internal 3.3V LDO powers a downstream low-current MCU. Compared to the CH340, the MCP2221 offers better Linux compatibility and a stable HID driver that does not require kernel-mode access.
Recommended
Industrial Configuration and Diagnostic Port
The MCP2221-I/ST is a strong fit for industrial configuration and diagnostic ports where field engineers attach a laptop to a programmable logic controller, variable-frequency drive, or industrial sensor via USB. The part operates over the industrial -40 C to +85 C temperature range and integrates the USB transceiver and 3.3V LDO, simplifying sealed-enclosure designs where space and connector count are at a premium. The I2C bus can directly read configuration EEPROMs and the UART can stream diagnostic logs from a service processor. Compared to the CP2102N, the MCP2221 offers GPIO access for door-interlock or status-LED wiring inside the enclosure.
Recommended
PC-Side I2C Peripheral Evaluation
The MCP2221-I/ST is widely used by PC-side engineers evaluating I2C peripherals during bench characterization. The HID interface means engineers can plug the dongle into any PC, run the Microchip configuration utility, and immediately see register reads on a graphical display without writing custom driver code. The 4 GPIOs can be configured as interrupt-capture inputs, allowing engineers to monitor peripheral events in real time. The TSSOP-14 footprint fits on a low-cost evaluation dongle that can ship with development kits, and the I2C controller supports clock stretching for sensors that gate communications on ADC conversion completion.
Recommended
Recommended Products Summary
Engineering reference data for MCP2221-I/ST — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | MCP2221A-I/ST | MCP2221AT-I/ST | MCP2221-I/P |
|---|---|---|---|---|
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Package | TSSOP-14 | TSSOP-14 (same) | TSSOP-14 (same) | DIP-14 (different package, not pin-compatible) |
| USB Speed | Full-Speed (12 Mbps) | Full-Speed (12 Mbps) | Full-Speed (12 Mbps) | Full-Speed (12 Mbps) |
| Downstream Interfaces | I2C/SMBus + UART | I2C/SMBus + UART | I2C/SMBus + UART | I2C/SMBus + UART |
| I2C Max Speed | 1 MHz (Fast-Plus) | 1 MHz (Fast-Plus) | 1 MHz (Fast-Plus) | 1 MHz (Fast-Plus) |
| GPIO Count | 4 | 4 | 4 | 4 |
| Operating Voltage | 3.0 V to 5.5 V | 3.0 V to 5.5 V | 3.0 V to 5.5 V | 3.0 V to 5.5 V |
| USB Suspend Support | No | Yes | Yes | No |
| USB Type-C Detection | No | Yes | Yes | No |
Key Differentiators
- HID-class enumeration requires no custom driver install (vs CP2102N (requires VCP driver on Windows))
- Native USB-to-I2C hardware controller with clock stretching (vs FT232 (USB-to-UART only))
- 4 configurable GPIOs plus dedicated clock-output pin (vs CH340 (no GPIOs))
Design Notes
Route USB D+ and D- traces as a 90-ohm differential pair, length-matched within 2 mm. Place the VBUS decoupling capacitor (4.7 uF minimum) within 3 mm of pin 1, and the VDD33 1 uF bypass within 2 mm of pin 2. Keep the I2C SCL/SDA traces short and away from switching-regulator switching nodes to avoid injected noise; the internal I2C pull-ups are weak (typically tens of kohm) and intended only for short evaluation runs.
Do not assume the MCP2221-I/ST enumerates as a virtual COM port - it presents itself as a HID-class device. Applications that expect a COM port must use the Microchip HID DLL or libusb. Do not pull-up the GPIO pins externally above 3.3V when VDD33 is the active supply; if you must drive 5V on a GPIO, remove the internal pull-up via the HID configuration utility first.
For I2C bus speeds above 400 kHz, add external 2.2 kohm pull-ups on SCL and SDA - the internal pull-ups cannot meet the Fast-Plus 1 MHz rise-time specification. Place the pull-up resistors close to the MCP2221-I/ST end of the bus, not at the slave end, to keep rise time within the SMBus specification. Decouple VDD33 with both a 1 uF bulk and a 100 nF high-frequency cap in parallel.
Compliance Information
RoHS and REACH compliant per Microchip product page. Industrial temperature grade -40C to +85C ('I' suffix). Not AEC-Q100 qualified; for automotive USB bridging, see MCP2221A automotive variants.
