Datasheet

Document Reference No.: FT_000202

UM245R USB - Parallel FIFO Development Module Datasheet Version 1.04

Clearance No.: FTDI# 124

7 Module Configurations

7.1 BUS Powered Configuration

Figure 7.1 Bus Powered Configuration

Figure 7.1 illustrates the UM245R in a typical USB bus powered design configuration. This can easily be

done by fitting the jumper link on J2, as shown above. The UM245R is supplied in this configuration by

default. A USB Bus Powered device gets its power from the USB bus. Basic rules for USB Bus power

devices are as follows:

i) On plug-in to USB, the device must draw no more than 100mA.

ii) On USB Suspend the device must draw no more than 500μA (2.5mA if remote wake-up is

enabled).

iii) A Bus Powered High Power USB Device (one that draws more than 100mA) should use the

PWREN# pin to keep the current below 100mA on plug-in and 500μA/2.5mA on USB suspend.

iv) A device that consumes more than 100mA cannot be plugged into a USB Bus Powered Hub.

v) No device can draw more that 500mA from the USB Bus.

Interfacing the UM245R module to a microcontroller (MCU), or other logic for a bus powered design

would be done in exactly the same way as for a self powered design (see Section 7.2), except that the

MCU would take its power supply from the USB bus (either the 5V on the USB pin, or the 3.3V on the 3V3

pin).