F2M03GLA datasheet(21/44 Pages) ETC2

21 / 44 page

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

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.

Page 21(44)

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