53
W&T
Subject to error and alteration
USB Interfaces
USB <> 20mA Interface, #34211
The 34211 Interface permits galvanically isolated, bi-directio-
nal connection of active and passive 20mA devices with
computers having an USB port.
This Interface supports one data line in each direction and uses
galvanic isolation between the USB and the 20mA side in all
operating modes. The converter is contained in a plastic
housing for mounting on standardized rails according to EN
50022-35.
Power supply
The Interface requires no additional external power supply,
since it is powered through the USB. The current draw of the
device is max. 200mA.
To reduce the load of the supplying USB host or hub, the
Interface can however be powered by an external 5V power
supply. Suitable power supplies can be obtained from W&T
under article number 11053.
Galvanic isolation and ESD protection
Both ports on the Interface are galvanically isolated to 1kV from
each other. Galvanic isolation of the signals is accomplished
using fast opto-couplers; the driver and receiver chips on the
20mA side are supplied with power by a galvanically isolated
DC/DC converter.
All 20mA signal lines are protected against static discharge up
to a voltage of 15 kV according to IEC 801-2, Level 4.