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Design Notes

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  RS485 Transceivers Reduce Power and EMI &mdash DN102
  PDF, 80 Kb, File published: Apr 1, 1995
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  RS485 Transceivers Reduce Power and EMI – Design Note 102
  Dave Dwelley, Teo Yang Long, Yau Khai Cheong and Bob Reay
  Recent innovations in process and circuit design have
  enabled the release of three new RS485 transceivers:
  the LTC В®1481, LTC1483 and LTC1487. These devices
  share an improved receiver circuit which features 80ОјA
  quiescent current operation (driver disabled) with no
  loss in AC performance relative to standard RS485
  devices, and a new 1ОјA shutdown mode (Figure 1). All
  three new devices are pin compatible with the industry
  standard LTC485 pinout, and feature Linear Technology’s exclusive ±10kV ESD protection (Human Body
  Model) at the line I/O pins, eliminating the need for
  external ESD protection in most cases. LTC1483
  The LTC1483 is a reduced EMI version of the LTC1481
  intended for use in systems where electromagnetic
  interference concerns take precedence over high data
  rates. The LTC1483 driver slew rate is deliberately limited
  to reduce the high frequency electromagnetic emissions
  (Figures 2a and 2b) while improving signal п¬Ѓdelity by
  reducing reflections due to misterminated cables. The
  maximum operating frequency of the LTC1483 driver is
  limited to 250kbaud. All other performance parameters
  are unchanged from the LTC1481, including the low …

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  Low Power CMOS RS485 Transceiver &mdash DN39
  PDF, 137 Kb, File published: Sep 1, 1990
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  Low Power CMOS RS485 Transceiver – Design Note 39
  Robert Reay
  Introduction
  The EIA RS485 data transmission standard has become
  popular because it allows for balanced data transmission in a party line configuration. Users are able to
  configure inexpensive local area networks and multidrop communication links using twisted pair wire and
  the protocol of their choice.
  Previous RS485 transceivers have been designed using
  bipolar technology because the common mode range
  of the device must extend beyond the supplies and be
  immune to ESD damage and latchup. Unfortunately, the
  bipolar devices draw a large amount of supply current
  and are unacceptable for low power applications. The
  LTC В®485 is the п¬Ѓrst CMOS RS485 transceiver featuring ultra low power consumption (ICC = 500ОјA max.)
  without sacrificing ESD and latchup immunity.
  Proprietary Output Stage
  The LTC485 driver output stage of Figure 1 features
  a common mode range that extends beyond the supplies while virtually eliminating latchup and providing excellent ESD protection. Two Schottky diodes SD3
  and SD4 are added to a conventional CMOS inverter
  output stage. The Schottky diodes are fabricated by a
  proprietary modification to a standard N-well CMOS
  process. When the output stage is operating normally,
  the Schottky diodes are forward biased and have a …

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Manufacturer's Classification

• Interface > RS485/RS422 Transceivers
• Space & Harsh Environment > Military Hermetic (M)