WT11i-E-AI4 Bluegiga Technologies, WT11i-E-AI4 Datasheet - Page 18

• Manufacturer Part Number: WT11i-E-AI4
• Description: Bluetooth / 802.15.1 Modules WT11i Class1 2.1+EDR uFL Conn iWRAP 4
• Manufacturer: Bluegiga Technologies

Specifications of WT11i-E-AI4

• Rohs: yes
• Class: 1
• Sensitivity: - 83 dBm
• Operating Supply Voltage: 3.3 V
• Interface Type: UART, USB
• Antenna Connector Type: Chip
• Maximum Operating Temperature: + 85 C
• Dimensions: 35.75 mm x 14.5 mm x 2.6 mm
• Mounting Style: SMD/SMT

7 USB Interface
This is a full speed (12Mbits/s) USB interface for communicating with other compatible digital devices. WT11i
acts as a USB peripheral, responding to requests from a master host controller such as a PC.
The USB interface 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 v2.1 + EDR specification 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), WT11i only supports USB
Slave operation.
7.1 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-External, 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.
7.2 USB Pull-Up resistor
WT11i features an internal USB pull-up resistor. This pulls the USB_DP pin weakly high when WT11i 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 15k 5% pull-
down resistor (in the hub/host) when VDD_PADS = 3.1V. This presents a Thevenin resistance to the host of
at least 900. Alternatively, an external 1.5k 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.
7.3 USB 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 supply terminal must be an absolute minimum of 3.1V.
Bluegiga recommends 3.3V for optimal USB signal quality.
7.4 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 for which to design, as the design is not limited by the power that can be drawn from the USB
hub or root port. However, it requires that VBUS be connected to WT11i via a resistor network (Rvb1 and
Rvb2), so WT11i can detect when VBUS is powered up. BlueCore4-External 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
pullup purposes. A 1.5k 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 is only suitable for bus-powered USB devices, e.g., dongles.
Bluegiga Technologies Oy
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