6B21 Analog Devices Inc, 6B21 Datasheet - Page 2

• Manufacturer Part Number: 6B21
• Manufacturer: Analog Devices Inc

Specifications of 6B21

• Lead Free Status / RoHS Status: Not Compliant

GENERAL DESCRIPTION
The 6B21 is a single-channel signal-conditioning module which
provides a digitally-controlled isolated current loop output to a
resolution of 12 bits. The output range can be selected to either
a 0 to 20 mA or 4 mA to 20 mA process current. It is electrically
and mechanically compatible with the 6B Series input modules
and backplanes. The 6B21 takes a command from the host
computer and converts it into an isolated process current
suitable for interfacing with valves and actuators. The 6B21
offers a normal mode output protection of 240 V rms as well as
1500 V rms CMV isolation. In addition the actual current
flowing in the current loop is read back by an on-board isolated
V/F (voltage-to-frequency) converter.
The 6B21 can be software-configured for address, output range,
baud rate, data format, checksum status, slew rate, and start-up
value. All programmable parameters are stored in the
nonvolatile memory of the module.
An on-board microcontroller communicates with the host
.
Rev. 0 | Page 2 of 8
Figure 2
through an RS-485 port to exchange command and status
information. An included EEPROM stores calibration constants
as well as configuration information. The microcontroller also
controls the output DAC through an optically-isolated serial
interface. The D/A converter drives the current loop through a
protective V/I (voltage-to-current) converter. The output
monitor is a V/F converter whose frequency is proportional to
the loop current. This variable signal frequency is fed back to
the microcontroller through an optical isolator. The
microcontroller then scales the frequency signal and returns the
current read-back data to the host computer. A DC/DC
converter generates 25 VDC from the +5 VDC power supply to
power the current loop and output circuitry.
.
6B21