BC352239A Datasheet, PDF (67/116 Pages) List of Unclassifed Manufacturers – BlueCore 3-Multimedia External

Device Terminal Descriptions
8.6.4 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 for, 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 BlueCore3-Multimedia External via a resistor network
(R_vb1 and R_vb2), so BlueCore3-Multimedia External can detect when VBUS is powered up.
BlueCore3-Multimedia 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
pull-up 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 i.e. dongles.
BlueCore3-Multimedia External
PIO
USB_DP
USB_DN
USB_ON
1.5KΩ 5%
R_s
R_s
R _vb1
R _vb2
D+
D-
VBUS
GND
Figure 8.23: 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.
BC352239A-ds-001Pc
© Cambridge Silicon Radio Limited 2004
Production Information
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