BC41B143A-ds-001Pe CSR, BC41B143A-ds-001Pe Datasheet - Page 67

• Manufacturer Part Number: BC41B143A-ds-001Pe
• Description: Blue Core ROM
• Manufacturer: CSR

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 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 BlueCore4-ROM via a resistor network (R
so BlueCore4-ROM can detect when VBUS is powered up. BlueCore4-ROM 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.
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:
BC41B143A-ds-001Pe
USB_ON is shared with BlueCore4-ROM PIO terminals
Identifier
R
R
R
vb1
vb2
s
Figure 10.14: USB Connections for Self Powered Mode
BlueCore4-ROM
Table 10.7: USB Interface Component Values
This material is subject to CSR’s non-disclosure agreement
USB_ON
USB_DN
USB_DP
© Cambridge Silicon Radio Limited 2005
PIO
27Ω nominal
22kΩ 5%
47kΩ 5%
Production Information
Value
1.5KΩ 5%
R
vb2
R
R
R
vb1
s
s
D+
D-
VBUS
GND
Impedance matching to USB cable
VBUS ON sense divider
VBUS ON sense divider
Device Terminal Descriptions
Function
Page 67 of 102
vb1
and R
vb2
),