THVD1500 Datasheet, PDF (15/29 Pages) Texas Instruments – 300 kbps RS-485 Transceivers With 8-kV IEC ESD Protection

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9 Application and Implementation
THVD1500
SLLSEY4 – JULY 2017
NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
9.1 Application Information
The THVD1500 is a half-duplex RS-485 transceiver commonly used for asynchronous data transmissions. The
driver and receiver enable pins allow for the configuration of different operating modes.
9.2 Typical Application
An RS-485 bus consists of multiple transceivers connecting in parallel to a bus cable. To eliminate line
reflections, each cable end is terminated with a termination resistor, R_T, whose value matches the characteristic
impedance, Z₀, of the cable. This method, known as parallel termination, allows for higher data rates over longer
cable length.
R
R
RE
DE
DD
A
B ^RT
AB
AB
A
R_{T B}
R
R
RE
DE
DD
R
D
R
D
R RE DE D
R RE DE D
Copyright © 2017, Texas Instruments Incorporated
Figure 18. Typical RS-485 Network With Half-Duplex Transceivers
9.2.1 Design Requirements
RS-485 is a robust electrical standard suitable for long-distance networking that may be used in a wide range of
applications with varying requirements, such as distance, data rate, and number of nodes.
9.2.1.1 Data Rate and Bus Length
There is an inverse relationship between data rate and cable length, which means the higher the data rate, the
shorter the cable length; and conversely, the lower the data rate, the longer the cable length. While most RS-485
systems use data rates between 10 kbps and 100 kbps, some applications require data rates up to 300 kbps at
distances of 4000 feet and longer. Longer distances are possible by allowing for small signal jitter of up to 5 or
10%.
Copyright © 2017, Texas Instruments Incorporated
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