SH7280 Datasheet, PDF (1407/1726 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperHTM RISC engine family

Section 25 USB Function Module
25.10 Example of USB External Circuitry
USD+ Pull-Up Control: In a system where it is wished to delay USB host/hub connection
notification (USD+ pull-up) (during high-priority processing or initialization processing, for
example), USD+ pull-up is controlled using a general output port. When the USB cable has been
connected to the host or hub and USD+ pull-up is inhibited, USD+ and USD– are placed in the
low level state (USD+ and USD– are pull down on the host or hub side) and the USB module
recognizes as if the USB bus reset has been received from the host. In that case, the USD+ pull-up
control signal and VBUS pin input signal should be controlled using a general output port and the
USB cable VBUS (AND circuit) as shown in figure 25.27. (The UDC core of this LSI holds the
powered state independent of USD+ and USD– state when the VBUS pin is low level.)
Detection of USB Cable Connection/Disconnection: As USB states are managed by hardware in
this module, a VBUS signal that recognizes connection/disconnection is necessary. The power
supply signal (VBUS) in the USB cable is used for this purpose. However, if the cable is
connected to the USB host/hub when the on-chip function LSI power is off, a voltage (5 V) will be
applied from the USB host/hub. Therefore, an IC (HD74LV1G08A, 2G08A, etc.) that allows
voltage application when the system power is off should be connected externally.
This LSI
PB10
USB module
VBUS
3.3 V
IC that allows
voltage application
when the system (LSI)
power is off.
USD+
USD-
IC that allows
voltage application
when the system (LSI)
power is off.
USB
connector
VBUS _{5 V}
USD+
USD-
GND
Note: Operation cannot be guaranteed by this example.
When the system requires countermeasures against external surge
or ESD noise, use the protection diode or noise canceler.
USB
cable
Figure 25.27 Example of USB Function Module External Circuitry
(For On-Chip Transceiver)
Rev. 1.00 Jun. 26, 2008 Page 1377 of 1692
REJ09B0393-0100