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

as VOD = VA – VB is positive. When D is low, the output states reverse: B turns high, A becomes low, and VOD is

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

default. The D pin has an internal pull-up resistor to VCC, thus, when left open while the driver is enabled, output

A turns high and B turns low.

Table 7-1. Driver Function Table

INPUT

ENABLE

OUTPUTS

FUNCTION

D

DE

A/Y

B/Z

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

defined as VID = VA – VB is higher than the positive input threshold, VTH+, the receiver output, R, turns high.

When VID is lower than the negative input threshold, VTH-, the receiver output, R, turns low. If VID is between

VTH+ and VTH- the output is indeterminate.

When RE is logic high or left open, the receiver output is high-impedance and the magnitude and polarity of VID

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 to one another (short-circuit), or the bus is not

actively driven (idle bus).

Table 7-2. Receiver Function Table

DIFFERENTIAL INPUT

ENABLE

OUTPUT

FUNCTION

VID = VA – VB

RE

R

VTH+ < VID

L

H

Receive valid bus high

VTH- < VID < VTH+

L

?

Indeterminate bus state

VID < VTH-

L

L

Receive valid bus low

X

H

Z

Receiver disabled

X

OPEN

Z

Receiver disabled by default

Open-circuit bus

L

H

Fail-safe high output

Short-circuit bus

L

H

Fail-safe high output

Idle (terminated) bus

L

H

Fail-safe high output

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THVD2410V-EP, THVD2450V-EP, THVD2452V-EP

SLLSFQ9B – MAY 2024 – REVISED OCTOBER 2024

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