BC41B143A-ANN-E4 ETC, BC41B143A-ANN-E4 Datasheet - Page 63

• Manufacturer Part Number: BC41B143A-ANN-E4
• Description: Bluecore 4-rom CSP EDR Single Chip Bluetooth v2.0 + EDR System
• Manufacturer: ETC

Device Terminal Descriptions
11.5
USB Interface
BlueCore4-ROM CSP 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 a set of
USB speakers.
USB is a master/slave oriented system (in common with other USB peripherals). BlueCore4-ROM CSP only
supports USB slave operation.
11.5.1 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 CSP 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. Typically these resistors are between 22Ω and 27Ω.
11.5.2 USB Pull-Up Resistor
BlueCore4-ROM CSP features an internal USB pull-up resistor. This pulls the USB_DP pin weakly high when
BlueCore4-ROM CSP 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. 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.
11.5.3 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.
11.5.4 Self-powered Mode
In self-powered mode, the circuit is powered from its own power supply and not from the VBUS (5V) line of the
USB cable. It draws only a small leakage current (below 0.5mA) from VBUS on the USB cable. This is the easier
mode to design for because the design is not limited by the power that can be drawn from the USB hub or root
port. However, it requires that VBUS is connected to BlueCore4-ROM CSP via a resistor network (R
and R
),
vb1
vb2
so BlueCore4-ROM CSP can detect when VBUS is powered up. BlueCore4-ROM CSP will not pull USB_DP high
when VBUS is off.
Self-powered USB designs (powered from a battery or PSU) must ensure that a PIO line is allocated for USB
pull-up purposes. A 1.5kΩ 5% pull-up resistor between USB_DP and the selected PIO line should be fitted to the
design. Failure to fit this resistor may result in the design failing to be USB compliant in self-powered mode. The
internal pull-up in BlueCore-4 ROM CSP is only suitable for bus-powered USB devices (dongles, for example).
This material is subject to CSR’s non-disclosure agreement
BC41B143A-ds-002Pd
Page 63 of 89
Production Information
© Cambridge Silicon Radio Limited 2005