RT

RT

R

A

B

R RE DE

D

D

R

A

B

R RE DE

D

D

R

D

R

RE

DE

D

A

B

R

D

R

RE

DE

D

A

B

15

THVD1500

www.ti.com

SLLSEY4A – JULY 2017 – REVISED NOVEMBER 2018

Product Folder Links: THVD1500

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Copyright © 2017–2018, Texas Instruments Incorporated

9 Application and Implementation

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, RT, 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.

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%.