Datasheet

MCP2221
DS20005292A-page 18  2014 Microchip Technology Inc.
1.6.2.3 3.3V Self Powered
Typically, many embedded applications are using 3.3V
power supplies. When such option is available in the
target system, MCP2221 can be powered up from the
existing 3.3V power supply rail. The typical connections
for MCP2221 are shown in Figure 1-5.
In this example, MCP2221 has both V
DD and VUSB
lines tied to the 3.3V rail. These tied connections
disable the internal USB transceiver LDO of the
MCP2221 to regulate the power supply on VUSB pin.
Another consequence is that the ‘1’ logical level on the
GPIO pins will be at the 3.3V level, in accordance with
the variations specified in Section 4.1 “DC
Characteristics”.
1.6.2.4 Remote Wakeup Capability
The MCP2221 offers a mechanism for triggering a
remote wakeup event for the USB host. The remote
wakeup trigger works only with the external interrupt
detector.
In order to use this capability, GP1 must be designated
for interrupt detection operation. Before the USB host
goes into Sleep/Standby, the interrupt detector must be
set up for detecting positive edges, negative edges, or
both; and also, the detector flag must be cleared. After
these conditions are met, the USB host can go into
Sleep/Standby mode and it will be awakened whenever
an external signal on GP1 triggers the interrupt detec-
tor.
FIGURE 1-5: USING AN EXTERNALLY
PROVIDED 3.3V POWER
SUPPLY
1.7 Pin Mux Module
The Pin Mux Module offers multiple functionalities for
the GP pins.
1.7.1 CONFIGURABLE PIN FUNCTIONS
The pins can be configured as:
• GPIO – individually configurable general purpose
input or output
• SSPND – USB Suspend state
• USBCFG – indicates USB configuration status
• LED_URX – indicates UART receive traffic (when
seen from the MCP2221)
• LED_UTX – indicates UART transmit traffic (when
seen from the MCP2221)
• LED_I2C – indicates I
2
C traffic
• ADC1/2/3 – analog inputs connected to the
internal 10-bit ADC
• DAC1/2 – analog outputs connected to the same
5-bit DAC
• CLKR – digital clock output (the nominal value is
12 MHz, but other values are possible)
• IOC – external interrupt detector
1.7.1.1 GPIO Pin Function
When the GPIO pin function is enabled for a given
GP(n) pin, it will operate as a digital input or an output
pin. When configured as a digital output, its value is
controlled through the USB HID commands. When
configured as a digital input, its logic value is read using
USB HID commands.
1.7.1.2 SSPND Pin Function
The SSPND pin (if enabled) reflects the USB state
(Suspend/Resume). The pin is active low (factory
default setting, see CHIPSETTING0 register for more
details) when the Suspend state has been issued by
the USB host. Likewise, the pin drives high after the
Resume state is achieved.
This pin allows the application to go into Low Power
mode when USB communication is suspended, and
switches to a full active state when USB activity is
resumed.
1.7.1.3 USBCFG Pin Function
The USBCFG pin (if enabled) starts out low (factory
default setting, see CHIPSETTING0 register for more
details) during Power-up or after Reset, and goes high
after the device successfully configures to the USB.
The pin will go low when in Suspend mode and high
when the USB resumes.
LDO
3.3V
D+
V
DD
VUSB
D-
IN
OUT
5V (USB Bus)
or external
power supply
External
USB
Transceiver
3.3V
LDO