BC352239A Datasheet, PDF (66/116 Pages) List of Unclassifed Manufacturers – BlueCore 3-Multimedia External

Device Terminal Descriptions
8.6 USB Interface
BlueCore3-Multimedia External devices contain a full speed (12Mbits/s) USB interface that is capable of driving a
USB cable directly. No external USB transceiver is required. The device operates as a USB peripheral,
responding to requests from a master host controller such as a PC. Both the OHCI and the UHCI standards are
supported. The set of USB endpoints implemented can behave as specified in the USB section of the Bluetooth
specification v1.2 or alternatively can appear as a set of endpoints appropriate to USB audio devices such as
speakers.
As USB is a Master/Slave oriented system (in common with other USB peripherals),
BlueCore3-Multimedia External only supports USB Slave operation.
8.6.1 USB Data Connections
The USB data lines emerge as pins USB_DP and USB_DN. These terminals are connected to the internal USB
I/O buffers of the BlueCore3-Multimedia External and therefore have a low output impedance. To match the
connection to the characteristic impedance of the USB cable, resistors must be placed in series with USB_DP /
USB_DN and the cable.
8.6.2 USB Pull-Up Resistor
BlueCore3-Multimedia External features an internal USB pull-up resistor. This pulls the USB_DP pin weakly high
when BlueCore3-Multimedia External is ready to enumerate. It signals to the PC that it is a full speed (12Mbit/s)
USB device.
The USB internal pull-up is implemented as a current source, and is compliant with Section 7.1.5 of the USB
specification v1.2. The internal pull-up pulls USB_DP high to at least 2.8V when loaded with a 15kΩ ±5%
pull-down resistor (in the hub/host) when VDD_PADS=3.1V. This presents a Thevenin resistance to the host of at
least 900Ω. Alternatively, an external 1.5kΩ pull-up resistor can be placed between a PIO line and D+ on the
USB cable. The firmware must be alerted to which mode is used by setting PS Key PSKEY_USB_PIO_PULLUP
appropriately. The default setting uses the internal pull-up resistor.
8.6.3 Power Supply
The USB specification dictates that the minimum output high voltage for USB data lines is 2.8V. To safely meet
the USB specification, the voltage on the VDD_USB supply terminals must be an absolute minimum of 3.1V.
CSR recommends 3.3V for optimal USB signal quality.
BC352239A-ds-001Pc
© Cambridge Silicon Radio Limited 2004
Production Information
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