bc41b143a07 ETC-unknow, bc41b143a07 Datasheet - Page 65

• Manufacturer Part Number: bc41b143a07
• Description: Single Chip Bluetooth
• Manufacturer: ETC-unknow

9.5.1
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, 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.
9.5.2
BlueCore4-ROM features an internal USB pull-up resistor. This pulls the USB_DP pin weakly high when
BlueCore4-ROM is ready to enumerate. It signals to the PC that it is a full speed (12Mbits/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 PSKEY_USB_PIO_PULLUP appropriately. The default
setting uses the internal pull-up resistor.
9.5.3
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.
CS-101564-DSP12
USB Data Connections
USB Pull-Up Resistor
USB Power Supply
Production Information
© CSR plc 2003-2007
Device Terminal Descriptions
Page 65 of 97