User manual

Using the AT90USBKey

AT90USBKey Hardware User Guide 2-7

7627A–AVR–04/06

2.2.2 VBUS Generator

When using the AT90USB microcontroller in USB host mode, the AT90USBKey should

provide a 5V power supply over the VBUS pin of its USB mini AB connector.

A couple of transistors allows the UVCON pin of the AT90USB to control the VBUS

generation (See Figure 2-3). In this mode the AT90USBKey is powered by external

battery power supply source.

Figure 2-3 . VBUS generator schematic

2.2.3 “POWER-ON“ LED

The POWER-ON LED (“D1”) is always lit when power is applied to AVRUSBKey

regardless of the power supply source.

R25

100k

BC847B

C19

4.7uF

R24

10k

FDV304P/FAI

UVCON

VBUS