MCP2221AT-ISLASHST datasheet(16/80 Pages) MICROCHIP

16 / 80 page

MCP2221A

DS20005565A-page 16

 2016 Microchip Technology Inc.

1.5

USB Module (HID, CDC and

Transceiver Modules)

The USB HID and CDC modules in the MCP2221A

are full-speed USB 2.0-compliant.

• Composite Device (CDC + HID):

- CDC: USB-to-UART Communications

- HID: I2C Transactions, GPIO Control,

Configuration and Miscellaneous Operations

(ADC, DAC, Clock Output)

• 128-byte buffer to handle data throughput at any

UART Baud Rate:

- 64-Byte Transmit

- 64-Byte Receive

• Fully configurable VID and PID assignments and

descriptors (stored on-chip)

• Bus Powered or Self Powered

1.5.1

DESCRIPTORS

During configuration, the supplied PC interface stores

the descriptors in the MCP2221A.

1.5.2

SUSPEND AND RESUME

The USB Suspend and Resume signals are supported

for power management of the MCP2221A. The device

enters Suspend mode when “Suspend Signaling” is

detected on the bus.

The MCP2221A exits Suspend mode when any of the

following events occur:

• “Resume Signaling” is detected or generated

• A USB “Reset” signal is detected

• A device Reset occurs

1.6

USB Transceiver

The MCP2221A has a built-in USB 2.0 full-speed

transceiver internally connected to the USB module.

The USB transceiver obtains power from the VUSB pin,

which is internally connected to the 3.3V regulator. The

best electrical signal quality is obtained when VUSB is

locally bypassed with a high-quality ceramic capacitor.

1.6.1

INTERNAL PULL-UP RESISTORS

The MCP2221A devices have built-in pull-up resistors

designed to meet the requirements for full-speed USB.

1.6.2

MCP2221A POWER OPTIONS

The following are the main power options for the

MCP2221A:

• USB Bus Powered (5V)

• 3.3V Self Powered

1.6.2.1

Internal Power Supply Details

MCP2221A offers various options for power supply. To

meet the required USB signaling levels, the

MCP2221A incorporates an internal LDO that is used

solely by the USB transceiver to present the correct

D+/D- voltage levels.

Figure 1-2 shows the internal connections of the USB

transceiver LDO in relation to the VDD power supply

rail. The output of the USB transceiver LDO is tied to

the VUSB line. A capacitor connected to the VUSB pin is

required if the USB transceiver LDO provides the 3.3V

supply to the transceiver.

FIGURE 1-2:

MCP2221A INTERNAL

POWER SUPPLY DETAILS

LDO

3.3V

USB

Transceiver

D+

VDD

VUSB

D-

OUT

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