CN-0313 Datasheet, PDF (1/5 Pages) Analog Devices – EMC Compliant RS-485 Transceiver Protection Circuits

Circuit Note
CN-0313
Circuits from the Lab™ reference circuits are engineered and
tested for quick and easy system integration to help solve today’s
analog, mixed-signal, and RF design challenges. For more
information and/or support, visit www.analog.com/CN0313.
Devices Connected/Referenced
ADM3485E
±15 kV ESD-Protected, 3.3 V,12 Mbps,
EIA RS-485 Transceiver
EMC Compliant RS-485 Transceiver Protection Circuits
EVALUATION AND DESIGN SUPPORT
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CN-0313 Circuit Evaluation Board (EVAL-CN0313-SDPZ)
Design and Integration Files
Schematics, Layout Files, Bill of Materials
CIRCUIT FUNCTION AND BENEFITS
The circuits shown in Figure 1 demonstrate proven and tested
electromagnetic compatibility (EMC) compliant solutions for
three protection levels for popular RS-485 communication ports
using the ADM3485E transceiver. Each solution was tested and
characterized to ensure that the dynamic interaction between
the transceiver and the protection circuit components functions
correctly together to protect against the electrostatic discharge
(ESD), electrical fast transients (EFT), and surge immunity
specified in IEC 61000-4-2, IEC 61000-4-4, and IEC 61000-4-5,
respectively. The circuits offer proven protection for RS-485
interfaces using the ADM3485E to the ESD, EFT, and surge
levels often encountered in harsh environments.
V_CC
V_CC
ADM3485E
RO
B
RE
120Ω
A
DI
DE
TVS
CDS0T23-SM712
PROTECTION SCHEME 1. TVS
ADM3485E
RO
B
TBU
TBU-CA065-200-WH
RE
120Ω
A
DI
DE
TISP
TISP4240M3BJR-S
TVS
CDS0T23-SM712
PROTECTION SCHEME 2. TVS/TBU/TISP
V_CC
ADM3485E
RO
B
TBU
TBU-CA065-200-WH
RE
120Ω
A
GDT
DI
2038-15-SM-RPLF
DE
TVS
CDS0T23-SM712
PROTECTION SCHEME 3. TVS/TBU/GDT
Figure 1. Three EMC Compliant ADM3485E Protection Circuits (Simplified Schematic, All Connections Not Shown)
Rev. 0
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