The MAX148X2 evaluation kit (EV kit) is a fully assembled
and tested PCB that demonstrates the functionality of the
MAX14855 isolated RS-485/RS-422 transceiver. The EV
kit operates from a single 3.3V supply and features an
on-board isolated power supply to power the secondary
side of the circuit.
The MAX148X2EVKIT may also be used to evaluate the
MAX14853, MAX14857, and MAX14859.
The EV kit is fully assembled and tested. Follow the steps
below to verify board operation.
Set the DC power supply to 3.3V and connect the
DC power supply between the EV kit’s VDDA and
GNDA connectors.
Ensure that J2 and J3 are in their default positions
(see
Table 1).
Turn on the power supply.
Set the signal/function generator to output a 1MHz
0-to-3V square wave.
NOTE: Set the signal/function
generator to operate with a high-impedance load. If the
function generator does not have that option, the R1 pad is
available to add a 50Ω impedance to ground.
Features
●
Operates from a Single 3.3V Supply
●
Terminal Block Connectors for Easy RS-485/RS-422
Evaluation
●
2750VRMS Isolation for 60s
●
Fully Assembled and Tested
5)
6)
Connect the signal/function generator to the TXD
test point.
Verify that the Y and Z outputs switch as the signal toggles.
Quick Start
Required Equipment
●
MAX148X2EVKIT
●
3.3V, 1A DC power supply
●
Signal/function generator
●
Oscilloscope
Ordering Information
appears at end of data sheet.
19-7567 ; Rev 2; 7/16
MAX148X2 Evaluation Kit
Evaluates: MAX14853/MAX14855/
MAX14857/MAX14859
Resistors R2–R4 Configuration
For end-of-the-line transceivers, close J4 and/or J7 to
connect a 120Ω termination resistor (R3) between the Y
and Z driver outputs and/or (R6) the A and B inputs on
the MAX14855.
Pullup and pulldown resistors are generally used on the
receiver inputs to guarantee a known state in the event
that all nodes on the bus are in receive mode, or the cable
becomes disconnected. The exact value for these resistors
will vary with the application. Pads are provided for pullup
(R2, R5) and pulldown (R4, R7) resistors, although the
use of these resistors is purely optional. Note that the
MAX14855 features true fail-safe receiver inputs, which
ensures that RXD is high when the receiver inputs are
shorted, open, or connected to an idle bus.
Detailed Description of Hardware
The MAX148X2 EV kit is a fully assembled and tested
circuit board for evaluating the MAX14855 isolated
RS-485/RS-422 transceiver (U1). The EV kit has been
designed to allow for evaluating the MAX14855 alone or
in a standard RS-485 configuration. The EV kit is powered
from a single 3.3V power supply.
External Power Supply
The power on the EV kit is derived from a single 3.3V
source. Connect an external supply to the VDDA test
point or the P1 connector to supply the 3.3V to the logic-
side (A) of the circuit. The integrated push-pull transformer
driver and external transformer, TX1, generate an isolated
supply for powering the isolated side (B) of the board.
Evaluating the Isolated RS-485/RS-422 Interface
Driver and Receiver Enable Selection
The MAX148X2 EV kit features three jumpers (J1, J2, and
J3) to enable/disable the driver and receiver outputs. Set
J1 to 2-3 to enable the receiver. Set J2 to 1-2 to enable
the driver. To actively control both enables, remove J1
and J2 and close J3, which connects DE and
RE
together.
Selecting a Transformer
Table 2
is a list of transformers designed to operate
with the MAX14855 family. Select the transformer that
best meets the performance requirements of the end
application. All transformers in
Table 2
can be used on the
MAX148X2 EV kit.
Table 1. Jumper Table (J1-J7)
JUMPER
J1
J2
J3
J4
J5
J6
J7
*Default position.
SHUNT POSITION
1-2
2-3*
1-2*
2-3
Open*
Closed
Open*
Closed
Open*
Closed
Open*
Closed
Open*
Closed
DESCRIPTION
Receiver is disabled. RXD is high impedance.
Receiver is enabled. RXD is active.
Driver is enabled.
Driver is disabled.
DE and
RE
are not connected together.
DE and
RE
are connected together.
Y and Z are not connected through the on-board 120Ω resistor.
Connects the on-board 120Ω resistor between Y and Z.
Z is not connected to B.
Z is connected to B (loopback mode).
Y is not connected to A.
Y is connected to A (loopback mode).
A and B are not connected through the on-board 120Ω resistor.
Connects the on-board 120Ω resistor between A and B.
www.maximintegrated.com
Maxim Integrated
│
2
MAX148X2 Evaluation Kit
Evaluates: MAX14853/MAX14855/
MAX14857/MAX14859
Table 2. Transformer Selection
MANUFACTURER/PART NUMBER
HALO TGMS-1455V6LF
HALO TGMS-1450V6LF
HALO TGMR-1455V6LF
HALO TGMR-1450V6LF
WURTH 750315227
WURTH 750315225
WURTH 750315231
WURTH 750315229
TURNS RATIO
1CT: 1.5CT
1CT:1CT
1CT:1.5CT
1CT:1CT
1CT:1.7CT
1CT:1.1CT
1CT:1.7CT
1CT:1.1CT
ISOLATION
VOLTAGE
(V
RMS
)
2750
2750
5000
5000
2750
2750
5000
5000
A-SIDE
SUPPLY (V)
3.3V
5V
3.3V
5V
3.3V
5V
3.3V
5V
CAN BE USED WITH
MAXIM PART NUMBERS
MAX14853, MAX14855
MAX14853, MAX14855
MAX14857,MAX14859
MAX14857,MAX14859
MAX14853, MAX14855
MAX14853, MAX14855
MAX14857,MAX14859
MAX14857,MAX14859
Component Information, PCB Layout,
and Schematic
●
MAX148X2 EV BOM
●
MAX148X2 EV PCB Layout
●
MAX148X2 EV Schematic
Ordering Information
PART
MAX148X2EVKIT#
#Denotes RoHS compliant.
TYPE
EV Kit
See the following links for component information, PCB
layout diagrams, and schematic:
www.maximintegrated.com
Maxim Integrated
│
3
MAX148X2 Evaluation Kit
Evaluates: MAX14853/MAX14855/
MAX14857/MAX14859
Revision History
REVISION
NUMBER
0
1
2
REVISION
DATE
3/15
2/16
7/16
Initial release
Removed MAX14859 part number
Added MAX14859 part number
DESCRIPTION
PAGES
CHANGED
—
1, 3
1, 3
Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses
are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time.
Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.
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