Linear Technology DC1746A Demo Manual

DESCRIPTION
Demonstration circuit 1746A is an isolated RS485/RS422
μModule ® transceiver + power featuring the LTM
The demo circuit is a 2500V
RS485/RS422 transceiver interface. The demo circuit
features an EMI optimized circuit confi guration and printed
circuit board layout. All components are integrated into
the μModule transceiver. The demo circuit operates from
a single external supply on V
PERFORMANCE SUMMARY
SYMBOL PARAMETER
V Input Supply Range
CC
V Output Voltage
CC2
f Maximum Data rate
MAX
V Maximum Working Insulation Voltage
IORM
Common Mode Transient Immunity
OPERATING PRINCIPLES
The LTM2881 contains an isolated DC/DC converter, de-
livering power to V at 5V from the input supply, V
CC2
Isolation is maintained by the separation of GND and GND2
where signifi cant operating voltages and transients can
exist without affecting the operation of the LTM2881. The
logic side ON pin enables or shuts down the LTM2881.
RS485/RS422 signaling is controlled by the logic inputs
DE, DI, TE and RE. Connection to the transceiver pins (A,
B, Y and Z) allows full- or half-duplex operation on the
isolated side of the demo circuit. A full-/half-duplex switch
is included on the demo circuit to ease setting the system
confi guration. The SLO pin confi gures the slew rate of the
driver output pins Y and Z.
µModule Transceiver + Power
® 2881.
galvanically isolated
RMS
. The part generates the
CC
(T = 25°C)
A
CONDITIONS
LTM2881-5
LTM2881-3
I = 0mA to 100mA, DE = 0V
LOAD
SLO = V
CC2
GND to GND2
CC
DEMO MANUAL DC1746A
Isolated RS485/RS422
output voltage V
CC2
signaling across the isolation barrier using LTC's isolator
μModule technology.
Design fi les for this circuit board are available at
http://www.linear.com/demo
L, LT, LTC, LTM, μModule, Linear Technology and the Linear logo are registered trademarks of
Linear Technology Corporation. All other trademarks are the property of their respective owners.
Data is transmitted out the driver pins Y and Z from the
input DI with DE set on. Data is received through the dif-
.
ference in A and B to the output RO with RE set on.
The demo circuit has been designed and optimized for low
RF emissions. To this end some features of the LTM2881
are not available for evaluation on the demo circuit. The
logic supply voltage, V
All control signals are selectable by jumper programming
only, including ON, RE, DE, TE and SLO. The spare logic
channel D to D
IN OUT
LTM2881:
and communicates all necessary
MIN TYP MAX
4.5 5 5.5
3.0 3 3.6
4.7 5
20
560
400
30
, is tied to V on the demo circuit.
L CC
is not available.
UNITS
V
V
V
Mbps
V
DC
V
RMS
kV/μs
dc1746af
1