Data Rate (bps)

10000

1000

100

10

100

1k

10 k

100 k

1M

10 M

100 M

Conservative

Characteristics

5%, 10%, and 20% Jitter

Figure 8-2. Cable Length vs Data Rate Characteristic

Even higher data rates are achievable (that is, 50Mbps for the THVD2450) in cases where the interconnect is

short enough (or has suitably low attenuation at signal frequencies) to not degrade the data.

8.2.1.2 Stub Length

When connecting a node to the bus, the distance between the transceiver inputs and the cable trunk, known as

the stub, should be as short as possible. Stubs present a non-terminated piece of bus line which can introduce

reflections of varying phase as the length of the stub increases. As a general guideline, the electrical length, or

round-trip delay, of a stub should be less than one-tenth of the rise time of the driver, thus giving a maximum

physical stub length as shown in Equation 1.

L(STUB) ≤ 0.1 × tr × v × c

(1)

where

• tr is the 10/90 rise time of the driver

• c is the speed of light (3 × 108 m/s)

• v is the signal velocity of the cable or trace as a factor of c

8.2.1.3 Bus Loading

The RS-485 standard specifies that a compliant driver must be able to drive 32 unit loads (UL), where 1 unit

load represents a load impedance of approximately 12kΩ. Because the THVD24xxV-EP devices consist of 1/8

UL transceivers, connecting up to 256 receivers to the bus is possible.

THVD2410V-EP, THVD2450V-EP, THVD2452V-EP

SLLSFQ9B – MAY 2024 – REVISED OCTOBER 2024

www.ti.com

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