component
MCP2221A USB Bridge
Public Made by Adomby adom
USB-2.0 to UART and I2C bridge with GPIO, ADC, and DAC, appears as a CDC + HID composite device.
3D Model
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Symbol & Footprint
Schematic Symbol
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PCB Footprint
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Datasheet
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README
markdownMCP2221A
Microchip · USB Bridge · SOIC-14
The MCP2221A is a USB-2.0 to UART and I2C serial converter. It enumerates as a composite device (CDC for USB-to-UART, HID for I2C and configuration), and adds four GPIO pins with ADC and DAC functions. It is an easy way to bring USB connectivity, a serial port, and an I2C master into a design using standard OS drivers.
Pinout
| Pin | Name | Type | Function |
|---|---|---|---|
| 1 | VDD | power_in | Positive supply input, 3.0V to 5.5V operating range. Decouple with a local ceramic capacitor. |
| 2 | GP0 | bidirectional | General purpose I/O. Alternate functions: SSPND (OUT) signals USB Suspend state; LED_URx (OUT, factory default) indicates UART Rx activity. |
| 3 | GP1 | bidirectional | General purpose I/O. Alternate functions: CLKR clock reference output (12 MHz or configurable divide), ADC1 input, LED_UTx (factory default) UART Tx activity indicator, and IOC external interrupt edge detector. |
| 4 | RST | input | Active-low reset input with internal pull-up. Drive low to reset the device. |
| 5 | URx | input | UART receive data input. Accepts data from the external UART peer to be forwarded to the USB CDC interface. |
| 6 | UTx | output | UART transmit data output. Drives data received over the USB CDC interface to the external UART peer. |
| 7 | GP2 | bidirectional | General purpose I/O. Alternate functions: USBCFG (OUT, factory default) indicates USB enumeration complete; ADC2 analog input; DAC1 analog output. |
| 8 | GP3 | bidirectional | General purpose I/O. Alternate functions: LED_I2C (OUT, factory default) USB/I2C traffic indicator; ADC3 analog input; DAC2 analog output. |
| 9 | SDA | bidirectional | I2C serial data line (open-drain). Requires external pull-up. MCP2221A operates as I2C host up to 400 kHz. |
| 10 | SCL | bidirectional | I2C serial clock line (open-drain). Requires external pull-up. Driven by the MCP2221A as I2C host, up to 400 kHz. |
| 11 | VUSB | power_out | USB internal 3.3V regulator output. Must be locally bypassed with a high-quality ceramic capacitor. Do not use to power external loads. |
| 12 | D- | bidirectional | USB differential data line, negative. Connect to the D- line of the USB connector. Termination is integrated. |
| 13 | D+ | bidirectional | USB differential data line, positive. Connect to the D+ line of the USB connector. Termination is integrated. |
| 14 | VSS | power_in | Device ground reference. |
Key specifications
| Parameter | Value |
|---|---|
| Type | USB-to-UART + USB-to-I2C bridge |
| USB | Full-speed USB 2.0 (12 Mb/s), CDC + HID composite |
| UART | Up to 460.8 kbaud |
| I2C | Master, up to 400 kHz |
| GPIO | 4 pins with ADC (10-bit) and DAC (5-bit) functions |
| Supply voltage | 3.0 V to 5.5 V |
| Operating temperature | -40 C to 85 C |
Ordering variants
Same part, different packaging or reel option.
MCP2221AI/PMCP2221AI/SLMCP2221AI/STMCP2221AI/ML
CAD (KiCad official)
- Symbol:
mcp2221a.kicad_sym - Footprint:
mcp2221a.kicad_mod - 3D model: SOIC-14 body from KiCad
Package_SO/SOIC-14_3.9x8.7mm_P1.27mm. - 3D model files:
mcp2221a-etched.step/mcp2221a-etched.glbcarry the MPN laser-etched on the die in a toggleableAdom.LaserEtchgroup (Fusion-ready);mcp2221a.step/mcp2221a.glbare the bare package body.
Provenance
Data extracted from the manufacturer datasheet, not a distributor listing:
- Datasheet: Microchip datasheet (78 pp, sha256
ade28a45a0314e2f, retrieved 2026-08-17, tier: manufacturer) - Extractor:
ds2sf(Claude). Every pin and dimension is cited to a datasheet page; it refuses to fabricate. - CAD: KiCad official libraries (CC-BY-SA 4.0).