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Rev: b
Low power Bluetooth
™ Module with antenna- F2M03GLA
Datasheet
6.2.5 Bus-Powered Mode
In bus-powered mode the application circuit draws its current from the 5V VBUS supply on the USB cable.
F2M03 negotiates with the PC during the USB enumeration stage about power consumption.
When selecting a regulator, be aware that VBUS may go as low as 4.4V. The inrush current (when charging
reservoir and supply decoupling capacitors) is limited by the USB specification (see USB 1.1 specification,
section 7.2.4.1). Some applications may require soft-start circuitry to limit inrush current if more than 10µF
is present between VBUS and GND.
The 5V VBUS line emerging from a PC is often electrically noisy. Regulation down to e.g. VDD=3.3V should
include careful filtering of the 5V line to attenuate noise that is above the voltage regulator’s bandwidth.
Excessive noise on the VDD supply pins of F2M03 may result in reduced receive sensitivity and a distorted
transmit signal. Recommended voltage regulator for the F2M03 is presented in section 6.7.
US B +
US B –
USB O N
Connections to F2M03 for Bus-Powered Mode
Identifier
Value
Function
Rs
27Ω nominal
Impedance matching to USB cable
Rvb1
22kΩ -5%
VBUS ON sense divider
Rvb2
47kΩ - 5%
VBUS ON sense divider
USB Interface Component Values
Note:
USB ON is shared with F2M03’s PIO terminals.
© 2006 Free2move AB
Page 21(44)
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