UG-400 Datasheet, PDF (5/20 Pages) Analog Devices – Plug and play system evaluation

Hardware User Guide
UG-400
ISOLATED RS-485 AND RS-422
The isolated RS-485 and RS-422 port is implemented using the
ADM2587E signal and power isolated CAN transceiver. The
ADM2587E connects to UART2 of the ADSP-BF548 and is capable
of functioning at data rates of up to 500 kbit/sec. Figure 4 shows
a circuit diagram of the implementation of the ADM2587E on
the ezLINX hardware.
The RS-485/RS-422 node can be configured using Jumpers JP3,
JP4, JP19, and JP40. To configure the node as a half-duplex RS-485
node, connect JP3, JP4, and JP40. When JP3 and JP4 are fitted,
A to Y are connected and B to Z are connected. When JP3 and
JP4 are removed, the node is configured as a full-duplex RS-422
node. When JP19 is fitted, the A and B pins are terminated with
120 Ω. If termination is not required, remove JP19. When JP40
is connected, a pull-up resistor of 10 kΩ is connected to the
RxD pin (Pin 4) of the ADM2587E. Table 4 shows jumper
configurations for all the interfaces on ezLINX.
3.3V
The 3.3 V supply is connected to the VCC pins (Pin 2 and Pin 8)
to power the isoPower isolated power supply and the iCoupler
signal isolation of the ADM2587E. This generates an isolated
3.3 V on the VISOOUT pin (Pin 12) of the ADM2587E, which is
connected to the VISOIN pin (Pin 19).
A 6-pin screw terminal connector, J7, is used for easy access to the
A (Pin 2 of J7), B (Pin 3 of J7), Z (Pin 4 of J7), Y (Pin 5 of J7), and
RS-485_ISO_GND (Pin 1 and Pin 6 of J7) signals.
The AN-960 Application Note, RS-485/RS-422 Circuit Imple-
mentation Guide, provides more information about implementing
RS-485 and RS-422 circuits.
The ADM2587E contains isoPower technology that uses high
frequency switching elements to transfer power through the
transformer. Special care must be taken during PCB layout to
meet emissions standards. Refer to the AN-0971 Application
Note, Recommendations for Control of Radiated Emissions with
isoPower Devices, for details on board layout considerations.
UART2TX
UART2RX
#RE
DE
R111
10K
3.3V
JP40
U16
2
8 ^VCC
VCC
7
4 ^TxD
RxD
5
6 ^RE
DE
1
3 ^GND1
9 ^GND1
10 ^GND1
GND1
ADM2587E
RS485_ISO_3.3V
12
VISOOUT
19
VISOIN
13
Y ₁₅
Z
18
A ₁₇
B
11
GND2 ₁₄
GND2 ₁₆
GND2 ₂₀
GND2
JP19
R66
120R
GND
RS485_ISO_GND
JP3
++
JUMPER
JP4
++
JUMPER
J7
1
2
3
4
5
6
SCREW_6
RS485_ISO_GND
3.3V
RS485_ISO_3.3V
C151
10uF
C150 C155 C149
0.1uF 0.1uF 0.01uF
C154
10uF
C153 C156 C152
0.1uF 0.1uF 0.01uF
GND
RS485_ISO_GND
Figure 4. ADM2587E Isolated RS-485 and RS-422 Implementation
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