MCP2221 datasheet(18/80 Pages) MICROCHIP

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MCP2221

DS20005292B-page 18

 2015 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 VDD 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 the 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 Wake-Up Capability

The MCP2221 offers a mechanism for triggering a

remote wake-up event for the USB host. The remote

wake-up 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; 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

detector.

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 I2C 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

active

low

(factory-default setting; see the CHIPSETTING0

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 the 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+

VDD

VUSB

D-

OUT

5V (USB Bus)

or external

power supply

External

USB

Transceiver

3.3V

LDO

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