UM232R USB-Serial UART Development Module Datasheet Version 1.02

© Future Technology Devices International Ltd. 2005

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6. Module Configurations

6.1 Bus Powered Configuration

Figure 4 - Bus Powered Configuration

Figure 4 illustrates the UM232R module in a typical USB bus powered design configuration. This can easily be done

by fitting the jumper link on J2, as shown above. The UM232R 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.

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

configured as PWREN# and use it to keep the current below 100mA on plug-in and 500μA on USB suspend.

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

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

Interfacing the UM232R 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 6.2), except that the MCU or external logic would take

its power supply from the USB bus (either the 5V on the USB pin, or 3.3V on the 3V3 pin).

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12

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J1

J2