User's Manual

Stollmann

E + V GmbH

BlueMod+B20

Hardware reference

Author: bg Date of Saving: 28.03.07 Ref: BlueMod+B20_HWreference_V101.doc Revision: 1.00 Page 15 of 15

3.8.3 USB Self-Powered Mode

In USB self-powered mode, the BlueMod+B20 is powered from its own power sup-

ply and not from the USB Vbus line. In order to detect when the USB Vbus line is

powered up, the USB Vbus line is monitored by PIO4 through a voltage divider .

Rvb1

22k

27R

Rpu

1k5

Rvb2

47k

D+

D-

VBUS

GND

PIO2/USB-Pull_Up

USB_DP

USB_DN

PIO4/USB_ON

BlueMod+B20

Connections in self powered mode

VSUP

+3.3V

3.8.4 USB Bus-Powered Mode

In USB bus-powered mode, the BlueMod+B20 is powered from the USB Vbus line

by means of a Low Drop Out (LDO) Voltage Regulator. When choosing the LDO

Voltage Regulator for supplying the +3.3V power to the BlueMod+B20, some factors

that need to be considered are:

• The voltage specification for the USB Vbus line is +4.75V to +5.25V.

• The total current required (average and peak) for the design.

• The voltage regulator’s drop out voltage vs. output current.

• The voltage regulator’s power dissipation over the operating temperature range.

• Filtering requirements on the USB Vbus line to attenuate noise above the volt-

age regulator’s bandwidth.

• The suspend state current draw.