BC41B143A-DS-003PC Datasheet, PDF (59/94 Pages) List of Unclassifed Manufacturers – BlueCore 4-ROM Plug-n-Go Single Chip Bluetooth v2.0 + EDR System

Device Terminal Descriptions
10.5 USB Interface
BlueCore4-ROM Plug-n-Go 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 v2.0+EDR
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), BlueCore4-ROM Plug-n-Go only
supports USB Slave operation.
10.5.1 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 BlueCore4-ROM Plug-n-Go, 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.
10.5.2 USB Pull-Up Resistor
BlueCore4-ROM Plug-n-Go features an internal USB pull-up resistor. This pulls the USB_DP pin weakly high when
BlueCore4-ROM Plug-n-Go 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.
10.5.3 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.
BC41B143A-ds-003Pc
Advance Information
© Cambridge Silicon Radio Limited 2005
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