THVD1500 Datasheet, PDF (14/29 Pages) Texas Instruments – 300 kbps RS-485 Transceivers With 8-kV IEC ESD Protection

THVD1500
SLLSEY4 – JULY 2017
www.ti.com
When the receiver enable pin, RE, is logic low, the receiver is enabled. When the differential input voltage
defined as V_ID = V_A – V_B is positive and higher than the positive input threshold, V_IT+, the receiver output, R, turns
high. When V_ID is negative and lower than the negative input threshold, V_IT-, the receiver output, R, turns low. If
V_ID is between V_IT+ and V_IT- the output is indeterminate.
When RE is logic high or left open, the receiver output is high-impedance and the magnitude and polarity of V_ID
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).
Table 2. Receiver Function Table
DIFFERENTIAL INPUT
V_ID = V_A – V_B
V_IT+ < V_ID
V_IT- < V_ID < V_IT+
V_ID < V_IT-
X
X
Open-circuit bus
Short-circuit bus
Idle (terminated) bus
ENABLE
RE
L
L
L
H
OPEN
L
L
L
OUTPUT
R
H
?
L
Z
Z
H
H
H
FUNCTION
Receive valid bus high
Indeterminate bus state
Receive valid bus low
Receiver disabled
Receiver disabled by default
Fail-safe high output
Fail-safe high output
Fail-safe high output
14
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