1 Functional Overview

The MCP2222 is a USB-to-UART, USB-to-I²C, and USB-to-SPI bridge device that enables USB connectivity between USB host systems and peripheral devices with legacy UART, I²C, and/or SPI interfaces. The device integrates USB termination resistors and a USB oscillator, reducing the number of required external components.

Note: The MCP2222 is configured through the USB interface, while its UART, I2C, and SPI interfaces enable communication only with external devices. These interfaces cannot be used for the MCP2222 configuration.

The MCP2222 provides six multifunction I/O pins that can be configured to support the following functions:

General purpose I/O functionality: GPIO[5:0]
USB status indication: USBCFG, USBSPND
Clock output: CLKO
UART hardware flow control: CTS, RTS
Communication activity indication: TXA, RXA, I2CA, SPIA
I²C clock low timeout indication: I2CTO
SPI Chip Select outputs: CS[3:0]
Interrupt/alert inputs: ALRT[3:0]

The pin functions are summarized in Table 1-1 and are described in detail in the I/O Pin Settings section.

Table 1-1. Pinout Description
Pin Name	SSOP	QFN	Pin Type	Factory Default Function	Alternate Functions
IO0	19	12	I/O	GPIO0 - General purpose I/O 0; input with pull-up enabled	CS3 - SPI chip-select 3 output. ALRT0 - Interrupt0/Alert0 input. CTS - UART clear-to-send input.
IO1	18	11	I/O	GPIO1 - General purpose I/O 1; input with pull-up enabled	CS2 - SPI chip-select 2 output. I2CA - I²C activity output; open-drain. RTS - UART request-to-send output.
IO2	15	8	I/O	GPIO2 - General purpose I/O 2; input with pull-up enabled	CS1 - SPI chip-select 1 output. ALRT1 - Interrupt1/Alert1 input. RXA - RX activity output; open-drain.
IO3	5	18	I/O	CLKO - Clock reference output; 4 MHz	TXA - TX activity output; open-drain. I2CTO - I²C clock low timeout output. GPIO3 - General purpose I/O 3.
IO4	4	17	I/O	CS0 - SPI Chip-select 0 output; active low	USBCFG - USB enumerated indication; open-drain. ALRT2 - Interrupt2/Alert2 input. GPIO4 - General purpose I/O 4.
IO5	3	16	I/O	ALRT3 – Interrupt3/Alert3 input; pull-up enabled, falling edge detection	SPIA - SPI activity output. USBSPND - Indicates USB host is suspended. GPIO5 - General purpose I/O 5.
RX	17	10	I	UART RX input	N/A
TX	16	9	O	UART TX output	N/A
SCL	7	20	I/O	I²C clock	N/A
SDA	6	19	I/O	I²C data	N/A
SCK	10	3	O	SPI clock output	N/A
MOSI	8	1	O	SPI data Output	N/A
MISO	9	2	I	SPI data Input	N/A
DM	13	6	USB	USB data minus (D-)	N/A
DP	14	7	USB	USB data plus (D+)	N/A
V_USB	12	5	P	USB transceiver power pin. When the V_DD voltage is 5V, the pin is connected internally to a 3.3V LDO (externally, a high-quality ceramic bypass capacitor needs to be connected). When the V_DD voltage is 3.3V, the pin needs to be connected to 3.3V externally.	N/A
V_BUS	11	4	I	USB Bus voltage sense input	N/A
RST	2	15	I	RESET input	N/A
GND	1	14	P	Ground	N/A
V_DD	20	13	P	Device power supply, 3V or 5V	N/A
EP	—	21	—	Exposed Thermal Pad (EP)	Connect to GND Rail