19-3204; Rev 1; 11/08
MAX13487E Evaluation Kit
General Description
The MAX13487E evaluation kit (EV kit) is a fully assem-
bled and tested PCB that contains a half-duplex RS-
485/RS-422 AutoDirection-controlled transceiver with
ESD protection. The EV kit circuit features a differential
driver and receiver. The circuit’s receiver is a 1/4-unit
load for the RS-485 bus and can communicate up to
500kbps. The MAX13487E AutoDirection and reduced-
driver slew-rate features are demonstrated on the EV kit
circuit. The EV kit can also be used to evaluate the
MAX13488E IC, which can communicate up to 16Mbps.
Power for the transceiver circuit is provided by a MAX256
H-bridge DC/DC converter, which powers the isolated
section of the MAX13487E RS-485/RS-422 circuit. Input-
ripple current and radiated noise are minimized by using
an H-bridge design. The isolated H-bridge DC-DC con-
verter operates at 420kHz. Input power to the EV kit
circuit can be supplied by a +5V DC source.
The DC-DC converter circuit uses a surface-mount
transformer to provide galvanic isolation and a full-wave
rectifier, and provides a regulated +5V to the
MAX13487E. A MAX1659 linear low dropout (LDO) reg-
ulator provides the regulated output and up to 300mA
of current. The output current limit and thermal shut-
down provide for a robust isolated RS-485/RS-422
transceiver circuit and power supply. The transceiver
and power circuits and PCB are designed for
2500V
RMS
isolation.
o
Designed for 2500V
RMS
Isolation
o
1/4 RS-485 Unit Loading
o
500kbps Half-Duplex RS-485/RS-422
Communication
o
+5V DC Input Range
o
Isolated +5V Output
o
Center-Tapped Full-Wave Rectifier Output
o
420kHz Switching Frequency
o
Output Current Limit and Thermal Shutdown
o
Low-Cost Integrated-FET H-Bridge Design
o
Also Evaluates MAX13488E (After IC
Replacement)
o
Fully Assembled and Tested
Features
o
Demonstrates MAX13487E AutoDirection Feature
Evaluates: MAX13487E/MAX13488E
Ordering Information
PART
MAX13487EEVKIT#
TYPE
EV Kit
#Denotes
RoHS compliant.
Component List
DESIGNATION
C1
QTY
1
DESCRIPTION
10µF ±10%, 10V X7R ceramic
capacitor (1206)
Murata GRM31CR71A106K
0.47µF ±10%, 16V X7R ceramic
capacitor (0805)
Murata GRM219R71C474K
0.1µF ±10%, 16V X7R ceramic
capacitors (0603)
Murata GRM188R71C104K
1µF ±10%, 16V X7R ceramic
capacitor (0805)
Murata GRM21BR71C105K
30V, 1A Schottky diodes (SOD123)
Diodes Inc. B130LAW
15V, 350mW ±5% zener diode
(SOT-23)
Central Semiconductor CMPZ5245B+
DESIGNATION
JU1, JU3, JU4,
JU5, JU6
JU2
R1
R2, R9
R4, R5
R6, R8
R7
T1
QTY
5
1
1
2
2
2
1
1
DESCRIPTION
2-pin headers
3-pin header
39.2kΩ ±1% resistor (0603)
100kΩ ±5% resistors (0603)
270Ω ±5% resistors (0805)
220Ω ±5% resistors (0805)
120Ω ±5% resistor (0805)
500µH, 1.5W, 3:8-turn, 400kHz
transformer (6-pin Gull Wing)
HALO Electronics TGM-380NARL
Half-duplex, high-speed transceiver
(8 SO)
Maxim MAX13487EESA+
C2
1
C3, C5, C6, C7
4
C4
1
D1, D2
2
U1
1
D3
1
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim Direct 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
MAX13487E Evaluation Kit
Evaluates: MAX13487E/MAX13488E
Component List (continued)
DESIGNATION
U2
QTY
1
DESCRIPTION
Integrated primary-side controller
and H-bridge driver (8 SO-EP*)
Maxim MAX256ASA+
Linear regulator (8 SO)
Maxim MAX1659ESA+
15Mbps CMOS photocouplers
(5 SO)
CEL/NEC PS9151-A
Shunts (JU1–JU6)
Rubber bumpers
PCB: MAX13487E Evaluation Kit#
Component Suppliers
SUPPLIER
CEL/NEC
(California Eastern
Laboratories/NEC)
Central
Semiconductor
Corp.
Diodes, Inc.
PHONE
WEBSITE
408-588-2247 www.cel.com
U3
1
631-435-1110 www.centralsemi.com
805-446-4800 www.diodes.com
U4, U5
—
—
—
2
6
4
1
HALO Electronics,
650-903-3800 www.haloelectronics.com
Inc.
Murata
Electronics North
America, Inc.
770-436-1300
www.murata-
northamerica.com
*EP
= Exposed pad.
Note:
Indicate that you are using the MAX13487E or
MAX13488E when contacting these component suppliers.
Quick Start
Required Equipment
Before beginning, the following equipment is needed:
• One +5V 550mA current-limited power supply with
a built-in current meter
•
•
•
One voltmeter
One logic signal generator
One oscilloscope with a differential probe
Note:
The +5V supply powering the MAX13487E EV kit
must be current-limited at 550mA and the output load
current for the output should be limited to less than
300mA.
Detailed Description of Hardware
The EV kit features a MAX13487E IC in an 8-pin SO sur-
face-mount package and demonstrates the ESD-
protected MAX13487E RS-485/RS-422 AutoDirection
transceiver. The differential driver and receiver are con-
figured for half-duplex operation and communicate up
to 500kbps. The transceiver circuit is a 1/4-unit load on
the receiver’s bus.
The EV kit features PCB pads to ease interfacing with
the driver/receiver logic signals on the non-isolated side
using the TXD, RXD, and PGND pads, respectively. The
MAX13487E IC is powered from the isolated VOUT
supply. Photocoupler U4 provides isolation for the
receiver’s RO signal (RXD pad) and U5 provides isola-
tion for the data-in DI signal (TXD pad).
The EV kit demonstrates the MAX13487E slew-rate
limited driver, which minimizes EMI radiation.
Photocouplers U4 and U5 are rated for up to 15Mbps.
The MAX13487E receiver signal is provided at the RO
pin. The RO pin will give a logic-high if A-B > +200mV.
A logic-low is given if A-B < -200mV. Refer to the
Transmitting and Receiving
sections in the
Function
Tables
in the MAX13487E/MAX13488E IC data sheet
for additional information on the AutoDirection circuitry
operation. Also see the
AutoDirection and Receiver
Enable Selection
section in this document for configur-
ing the AutoDirection and receiver operation.
Procedure
The MAX13487E EV kit is fully assembled and tested.
Follow the steps below to verify board operation.
Caution: Do not turn on the power supply until all
connections are completed.
1) Connect a voltmeter to the VOUT and GND PC pads.
2) Verify that a shunt is not installed across the pins of
jumper JU1 (U2 enabled).
3) Verify that a shunt is installed across pins 1-2 of
jumper JU2 (U1 enabled).
4) Verify that a shunt is installed across the pins of
jumpers JU3 (AutoDirection enabled), JU4 (pull-
down), JU6 (pullup), and JU5 (bus terminated).
5) Connect the +5V power supply to the VIN pad.
Connect the power supply’s ground to the PGND pad.
6) Turn on the power supply and verify that the volt-
meter at VOUT reads +5V.
7) Using the logic signal generator, apply a +5V logic
signal to the TXD PCB pad and PGND.
8) Using the oscilloscope and differential probes, verify
the signal at the A-B pads (isolated side).
2
_______________________________________________________________________________________
MAX13487E Evaluation Kit
The EV kit input power is typically a +5V DC source that
provides at least 450mA of current to the MAX256 inte-
grated primary-side controller and H-bridge driver cir-
cuit. The MAX256 contains an on-board oscillator, pro-
tection circuitry, and internal H-bridge FETs to provide
power to the primary of the transformer T1. The MAX256
prevents cross conduction of the H-bridge MOSFETs by
implementing break-before-make switching. The
MAX256 programmable oscillator is programmed to
420kHz by resistor R1. The switching-frequency duty
cycle is fixed at 50% to control energy transfer to trans-
former T1 isolated output.
The MAX256 IC includes UVLO for controlled startup
and provides controlled turn-on during power-up and
during brownouts. If the input voltage at VIN falls below
1.9V (typ), the MAX256 IC will shut down.
Surface-mount transformer T1 provides galvanic isola-
tion and the VOUT output is powered from a center-
tapped full-wave rectifier circuit (D1 or D2) to reduce
output-voltage ripple. It feeds a MAX1659 LDO regula-
tor configured for +5V output. The LDO output is
current limited and features thermal shutdown to pro-
vide for a robust isolated supply at VOUT, which can
provide up to 300mA of current.
The two-layer PCB is designed for 2500V
RMS
isolation,
with 300 mils spacing between the PGND and GND
planes. The bottom PCB PGND plane under U2 is uti-
lized as a thermal heat sink for power dissipation of the
MAX256 thermally enhanced SO package. Test points
TP1 (PGND) and TP2 (GND) are provided on the PCB
for probing the respective ground plane or to connect
the PGND to GND planes for nonisolated evaluation of
the circuit.
Evaluates: MAX13487E/MAX13488E
Jumper Selection
The MAX13487E EV kit features several jumpers to
reconfigure the receiver/driver enable circuits, and shut-
down for the MAX256 and MAX13487E ICs. Additionally,
PCB pads are provided for connecting an external load
to the isolated +5V output at VOUT and GND.
Shutdown Control
The MAX13487E EV kit features two jumpers that con-
figure the shutdown mode of the circuit. Jumper JU1
configures the MAX256 DC-DC converter and JU2 con-
figures the MAX13487E IC for shutdown mode. See
Table 1 for placing the EV kit circuit or the desired IC in
shutdown mode.
AutoDirection and Receiver Enable Selection
The MAX13487E EV kit features a 2-pin jumper (JU3) to
set the MAX13487E receiver mode of operation,
AutoDirection, or receiver output enabled. Refer to the
AutoDirection Circuitry
section in the MAX13487E/
MAX13488E IC data sheet for more information on the
MAX13487E
RE
pin modes of operation. See Table 2
for configuring the receiver mode of operation using
jumper JU3.
Table 1. JU1 and JU2 Shutdown Mode Control
JU1 SHUNT
POSITION
Not installed
Installed
Not installed
MAX256 MODE PIN
Connected to VIN through R2
Connected to PGND
Connected to VIN through R2
JU2 SHUNT
POSITION
1-2
2-3
2-3
MAX13487E
SHDN
PIN
Connected to VOUT
Connected to GND
Connected to GND
EV KIT OPERATION MODE
All ICs operational
Shutdown
MAX13487E shutdown, all other
ICs operational
Table 2. Driver and Receiver JU3 Functions
SHUNT POSITION
Installed
Not installed
RE
PIN
Connected to VOUT
Connected to GND through R9
MAX13487E AUTODIRECTION OR RECEIVER MODE
AutoDirection enabled*
Receiver RO output enabled
*To
avoid bus contention, ensure that only one driver has control of the bus at a time.
_______________________________________________________________________________________
3
MAX13487E Evaluation Kit
Evaluates: MAX13487E/MAX13488E
RS-485 Bus Pullup/Pulldown and
Termination Resistors Configuration
Jumpers JU6 and JU4 are provided for connecting the
mandatory pullup and pulldown resistors onto the RS-485
bus A and B lines, respectively. Pullup resistor R8 and
pulldown resistor R6 define the voltage on the A and B
lines in conjunction with R7 when the driver input (DI) is
high. See Table 3 for configuring the pullup and pulldown
resistors. R6 and R8 can be higher valued if the
differential terminal resistor (R7) is not used.
Jumper JU5 is provided for terminating the A and B bus
lines when the MAX13487E EV kit is connected at the
end of an RS-485 bus. Resistor R7 provides 120Ω of ter-
mination when jumper JU5 is used. See Table 4 for con-
figuring the termination mode.
Table 3. JU6, JU4 Functions, Pullup, Pulldown Resistors
SHUNT POSITION
None
Installed
A AND B LINE SIGNAL
Not pulled up or down
A signal pulled up, connected to VOUT
B signal pulled down to GND
Table 4. JU5 Functions, Bus Termination
SHUNT POSITION
None
Installed
A-B PINS AND RS-485 BUS TERMINATION
Not terminated
Terminated
EV KIT BUS CONNECTION
Mid point
End of bus line
Evaluating the MAX13488E IC and
Other Transformer Configurations/Designs
MAX13488E Evaluation
The MAX13487E EV kit can also evaluate the
MAX13488E IC. To evaluate the MAX13488E, replace
IC U1 with the MAX13488E. Note that the MAX13488E
driver slew rate is not limited and allows transmission
speeds of up to 16Mbps. Refer to the MAX13487E/
MAX13488E IC data sheet for additional information.
Smaller Transformer and 2000V
RMS
Isolation Design
The EV kit’s two-layer PCB is designed for 2500V
RMS
isolation, with 300 mils spacing between the PGND and
GND planes. Additionally, transformer T1 is rated for
3000V
RMS
and is an integral part of the dielectric with-
stand voltage of the EV kit circuit. Photocouplers U4
and U5 are guaranteed to withstand 3750V
RMS
.
However, the circuit uses the isolated transformer to
transfer power from the primary side to the secondary
side and the withstand voltage of the transformer, as
well as photocouplers U4 and U5, so the PCB must be
considered when designing and testing the EV kit cir-
cuit. For example, if less than 2500V
RMS
isolation is
needed, a smaller 2000V
RMS
transformer may be used
to save board area, but then the entire circuit will have
only 2000V
RMS
of isolation.
4
_______________________________________________________________________________________
R1
39.2kΩ
1%
1
CK_RS
GND
GND
U2
6
MAX256
2
5
7
IN
MAX1659
GND
8
SET
1
GND
PGND
VIN
VOUT
C6
0.1μF
R4
270Ω
5
VDD
4
V0
GND
3
R9
100kΩ
2
RE
B
7
R7
120Ω
B
2
JU3
1
VIN
1
C7
0.1μF
2
3
JU2
3
SHDN
A
6
R8
220Ω
4
5
DI
GND
VOUT
JU6
R5
270Ω
1
5
ANODE VDD
U5
V0
CATHODE GND
2
3
4
VOUT
VOUT
U4 CATHODE
RO
V
CC
2
4
8
C5
0.1μF
R6
220Ω
1
ANODE
VOUT
GND
U3
3
D3
1
TP1
TP2
4
D2
5
3
4
MODE
ST2
1
JU1
2
C3
0.1μF
16V
C4
1μF
16V
IN
IN
OUT
1
T1
6
5
D1
3
2
SHDN
OUT
VOUT
4
7
6
ST1
VOUT
2
C1
10μF
10V
C2
0.47μF
16V
R2
100kΩ
VCC
3 VCC
8
VIN
VIN
PGND
Figure 1. MAX13487E EV Kit Schematic
JU4
GND
SHDN
RXD
PGND
U1
MAX13487E
JU5
A
Evaluates: MAX13487E/MAX13488E
_______________________________________________________________________________________
TXD
MAX13487E Evaluation Kit
5
单片机
京公网安备 11010802033920号
Copyright © 2005-2026 EEWORLD.com.cn, Inc. All rights reserved
电子工程世界
