Analog Integrated Circuit Device Data
Freescale Semiconductor
106
PC34708
Functional Block Requirements and Behaviors
Mini/Micro USB Interface Description and Application Information
7.10
Mini/Micro USB Interface Description and Application
Information
7.10.1 USB Interface
PC34708 provides the regulators required to power the PHY in the i.MX50, i.MX51, and i.MX53 processors, which are VUSB2
for USB OTG operation. The PC34708 is capable of identifying the type of the external power source, and selecting one of two
The PC34708 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 PC34708 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 PC34708 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 PC34708
is also able to identify some non-supported accessories, such as video cables, phone-powered devices, etc.
Figure 22. USB Interface
7.10.2 Supplies
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.
ID
VBUS
VUSB
VUSB2
UART
USB
Audio
GND
ID
VBUS
GOTG
VBUSVIN
VINUSB
VUSB
VINUSB2
VUSB2
DP
DM
TXD
RXD
D+
D-
SPKR
SPKRL
MIC
VBUS
M0
M1
MOTG
MPD
MVBUS
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
BP
2.5V USB Analog supply
To/from
Mini-USB
Connector