MC34708 datasheet(89/159 Pages) FREESCALE

89 / 159 page

Analog Integrated Circuit Device Data



Freescale Semiconductor

MC34708

Functional Block Description

7.8.4

Mini/Micro USB Switch

The MC34708 is able to multiplex the 5 pins to support UART and high-speed USB2.0 data communications, a mono/stereo-

audio/microphone headset, or other accessories. To identify what accessory is plugged into the Mini or Micro-USB connector,

the MC34708 supports various detection mechanisms, including the VBUS detection and ID detection. A highly accurate 5-bit

ADC is offered to distinguish the 32 levels of ID resistance, and to identify the button pressed in a cord remote control, while an

Audio Type 1 cable is attached. After identifying the accessory attached, the MC34708 configures itself to support the accessory

and interrupts a host via the INT pin. The processor can evaluate what caused the interrupt via the SPI/I2C bus. The MC34708

is also able to identify some non-supported accessories, such as video cables, phone-powered devices, etc.

Figure 20. USB Interface

7.8.4.1

Supplies

The MC34708 provides the regulators required to power the PHY in the i.MX50, i.MX51, and i.MX53 processors, which are

VUSB2 (detailed Linear Regulators (LDOs)), and VUSB. The IC also provides the 5.0 V supply for USB OTG operation.

The VUSB regulator is used to supply 3.3 V to the external USB PHY. The input to the VUSB regulator can be supplied from the

VBUS wire of the cable when supplied by a host (PC or Hub), or by the SWBST voltage via the VINUSB pin. The VUSB regulator

is powered from the SWBST boost supply to ensure OTG current sourcing compliance through the normal discharge range of

the main battery. The VUSBSEL SPI bit is used to make the selection between a host or OTG mode operation.

VBUS

VUSB

VUSB2

UART

USB

Audio

GND

VBUS

VINUSB

VUSB

VINUSB2

VUSB2

TXD

RXD

D+

D-

SPKR

SPKRL

MIC

VBUS

MOTG

Switches

Regulator

Detect

To/From

Application

Processor

To/From

Audio IC

To/From

Mini-USB

Connector

SWBST (5.0 V boosted supply)

3.3 V USB Analog supply

2.5V USB Analog supply

To/from

Mini-USB

Connector

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