Datasheet

Analog Integrated Circuit Device Data
Freescale Semiconductor 100
MC34708
Functional Block Description
Figure 30. UART Operation
7.8.4.12 USB Host (PC or HUB) Operation Mode
When the attached accessory is a USB host or hub, the ID pin floats. During normal operation, when setting the control bits, both
the D PLUS to DP and the D MINUS to DM switches are switched on (see Figure 31). The mini USB interface sets the bit USB
in the USB Device type register.
When SW_HOLD = 0, the switching action of D+ to DP and the D- to DM switches, are controlled by the WAIT bit. If WAIT = 1,
the signal switches will be turned on after a WAIT time. If WAIT = 0, the signal switches won't be turned on until the WAIT bit is
set to '1' by the SPI. When SW_HOLD = 1, regardless of what the WAIT is set to, '0' or '1', the signal switches are turned on once
the USB host is identified.
After the DPLUS to DP and the DMINUS to DM switches are turned on, the baseband can pull the DPLUS signal high to start
the USB attaching sequence.
The detachment is detected by the falling edge of the USBDETS signal. When the USBDETS falls, the Detach bit is set to inform
the baseband. The MC34708 USB detection then enters the Standby mode.
Figure 31. USB Operation
7.8.4.13 USB charger or Dedicated Charger Operation Mode
When the attached accessory is a USB Charger or Dedicated Charger, the MC34708 enables the bit USB Charge or the
Dedicated CHG in the USB Device type register. During normal operation when setting of the control bits, the D PLUS and D
MINUS switches are turned on for the USB Charger, but not for the Dedicated Charger.
The VBUS detector is used to monitor the detachment of the charger. The falling edge of USBDETS is an indication of charger
detachment. Unplugging the mini-USB connector and unplugging the AC side, both lead to the same detachment conclusion.
The Detach bit is set to inform the host. The MC34708 USB detection then enters the Standby mode.
VBUS
ID
D+
D-
GND
Baseband
SHLD
UART
Cable
RxD
TxD
DP
DM
ID
GND
UART
Interface
ADC
ID Det
VBUS
Det
UART
VBUS
`
VBUS
ID
D+
D-
GND
Baseband
SHLD
USB
Cable
DPLUS
DMINUS
DP
DM
ID
GND
USB
Host
ADC
ID Det
VBUS
Det
5V
USB Xcvr
VBUS