BC41B143A-DS-003PC Datasheet, PDF (60/94 Pages) List of Unclassifed Manufacturers – BlueCore 4-ROM Plug-n-Go Single Chip Bluetooth v2.0 + EDR System

Device Terminal Descriptions
10.5.4 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 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 BlueCore4-ROM Plug-n-Go via a resistor network (R_vb1 and R_vb2), so
BlueCore4-ROM Plug-n-Go can detect when VBUS is powered up. BlueCore4-ROM Plug-n-Go 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 is only suitable for bus-powered USB devices, e.g., dongles.
BlueCore
PIO
USB_DP
USB_DN
USB_ON
1.5KΩ
5% _Rs
R_s
R_vb1
D+
D-
VBUS
R_vb2
GND
Figure 10.13: USB Connections for Self-Powered Mode
The terminal marked USB_ON can be any free PIO pin. The PIO pin selected must be registered by setting
PSKEY_USB_PIO_VBUS to the corresponding pin number.
Note:
USB_ON is shared with BlueCore4-ROM Plug-n-Go PIO terminals.
Identifier
R_s
R_vb1
R_vb2
Value
27Ω nominal
22kΩ 5%
47kΩ 5%
Function
Impedance matching to USB cable
VBUS ON sense divider
VBUS ON sense divider
Table 10.6: USB Interface Component Values
BC41B143A-ds-003Pc
Advance Information
© Cambridge Silicon Radio Limited 2005
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