Datasheet

MCP2221
DS20005292A-page 16  2014 Microchip Technology Inc.
1.5 USB Module (HID, CDC and
Transceiver modules)
The USB HID and CDC modules in the MCP2221 are
full-speed USB 2.0 compliant.
• Composite device (CDC + HID):
- CDC: USB-to-UART Communications
- HID: I
2
C 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 MCP2221.
1.5.2 SUSPEND AND RESUME
The USB Suspend and Resume signals are supported
for power management of the MCP2221. The device
enters Suspend mode when “Suspend Signaling” is
detected on the bus.
The MCP2221 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 MCP2221 has a built-in USB 2.0 full-speed
transceiver internally connected to the USB module.
The USB transceiver obtains power from the V
USB 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 MCP2221 devices have built-in pull-up resistors
designed to meet the requirements for full-speed USB.
1.6.2 MCP2221 POWER OPTIONS
The following are the main power options for the
MCP2221:
• USB Bus Powered (5V)
• 3.3V Self Powered
1.6.2.1 Internal Power Supply Details
MCP2221 offers various options for power supply. To
meet the required USB signaling levels, the MCP2221
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 V
DD 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: MCP2221 INTERNAL
POWER SUPPLY DETAILS
LDO
3.3V
USB
Transceiver
D+
V
DD
VUSB
D-
IN
OUT