7 Detailed Description

7.1 Overview

The THVD1400 is a low-power, half-duplex RS-485 transceiver suitable for data transmission up to 500 kbps.

The THVD1420 is a low-power, half-duplex RS-485 transceiver suitable for data transmission up to 12 Mbps.

7.2 Functional Block Diagrams

R

D

DE

RE

B

A

GND

V

CC

7.3 Feature Description

Internal ESD protection circuits protect the transceiver against Electrostatic Discharges (ESD) according to IEC

61000-4-2 of up to ±12 kV (Contact Discharge), ±15 kV (Air Gap Discharge) and against electrical fast transients

(EFT) according to IEC 61000-4-4 of up to ±4 kV.

7.4 Device Functional Modes

When the driver enable pin, DE, is logic high, the differential outputs A and B follow the logic states at data input

D. A logic high at D causes A to turn high and B to turn low. In this case, the differential output voltage defined

negative.

When DE is low, both outputs turn high-impedance. In this condition, the logic state at D is irrelevant. The DE

pin has an internal pull-down resistor to ground; thus, when left open, the driver is disabled (high-impedance) by

A turns high and B turns low.

Table 7-1. Driver Function Table

INPUT

ENABLE

OUTPUTS

FUNCTION

D

DE

A

B

H

H

H

L

Actively drive bus high

L

H

L

H

Actively drive bus low

X

L

Z

Z

Driver disabled

X

OPEN

Z

Z

Driver disabled by default

OPEN

H

H

L

Actively drive bus high by default

When the receiver enable pin, RE, is logic low, the receiver is enabled. When the differential input voltage

are irrelevant. Internal biasing of the receiver inputs causes the output to go failsafe-high when the transceiver is

disconnected from the bus (open-circuit), the bus lines are shorted (short-circuit), or the bus is not actively driven

(idle bus).

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THVD1400, THVD1420

SLLSF78B – DECEMBER 2020 – REVISED OCTOBER 2021

Copyright © 2021 Texas Instruments Incorporated

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Product Folder Links: THVD1400 THVD1420