5b45-05 Analog Devices, Inc., 5b45-05 Datasheet - Page 2

• Manufacturer Part Number: 5b45-05
• Description: Isolated, Frequency Input
• Manufacturer: Analog Devices, Inc.

GENERAL DESCRIPTION
The 5B45 and 5B46 are single-channel isolated frequency input
modules that produce a 0 to +5V output proportional to input
frequency. Model 5B45 accepts full-scale inputs ranging from
500 Hz to 20 kHz. Model 5B46 accepts full-scale inputs ranging
from 20 kHz to 275 kHz. Both models allow the user to set the
threshold to either 0 V (for zero crossing signals) or +1.4 V (for
positive level signals), and the hysteresis to either +25 mV or
+400 mV (all input types).
The 5B45 and 5B46 protect the computer side from field-side
over-voltage faults. All models withstand 240 V rms at their
input terminals without damage, thereby shielding computer-
side circuitry from field-side over-voltage conditions. In
addition, all 5B45 and 5B46 models are mix-and match and hot-
swappable, so can be inserted or removed from any socket in
the same backplane without disrupting system power.
Inside 5B45 & 5B46 Modules – The 5B45/46 internal circuitry
compares the input signal to the user-selected threshold (V
and hysteresis (V
exceed the combined threshold and hystersis levels (V
+V
frequency. The comparator output is then transmitted across a
proprietary transformer-coupled isolation barrier and
converted to a high-level analog signal. This signal is then
filtered by a multi-pole low pass Butterworth filter and buffered
.
H
)will trigger a comparator at a rate determined by the input
H
). Signals of virtually any wave shape that
T
T
)
Rev. 0 | Page 2 of 8
Figure 2
to provide a low-noise, low-impedance output signal that is
accurately proportional to input frequency.
Simple Setup and Versatile Choices – Setting the threshold
and hysteresis values is a simple matter of externally wiring to
the backplane screw terminals. The threshold for measuring a
zero-crossing voltage waveform (such as sine waves) is set to 0
volts by connecting the input signal across screw-terminals 4
and 3. The threshold for a positive level signal (such as a TTL or
pulse train waveform) is set at +1.4V by connecting the input
signal across terminals 3 and 2. Hysteresis for both input signal
types is set at +400 mV but can be changed to +25 mV by
adding a jumper between screw terminals 1 and 4. Response
time is a function of a modules rated input frequency range.
(See the 5B45 and 5B46 Model Table).
The input circuit is fully floating and isolated from the output
and power commons. In addition, the output section acts as a
third floating port towards eliminating possible problems from
ground loops and power supply noise. The output common
must be held within +3V of power common.
A series output switch eliminates the need for external
multiplexing in many applications. The switch is turned on by
an active-low enable input. If the switch is to be on at all times,
the enable-input should be grounded to power common as it is
on the 5B01 and 5B08 backplanes..
5B45 / 5B46
.