THVD1500 Datasheet, PDF (13/29 Pages) Texas Instruments – 300 kbps RS-485 Transceivers With 8-kV IEC ESD Protection

THVD1500
www.ti.com
8 Detailed Description
SLLSEY4 – JULY 2017
8.1 Overview
The THVD1500 is a low-power, half-duplex RS-485 transceiver suitable for data transmission up to 300 kbps.
8.2 Functional Block Diagrams
V_CC
R
RE
A
DE
B
D
GND
Copyright © 2017, Texas Instruments Incorporated
8.3 Feature Description
Internal ESD protection circuits protect the transceiver against Electrostatic Discharges (ESD) according to IEC
61000-4-2 of up to ±8 kV (Contact Discharge), ±10 kV (Air Gap Discharge) and against electrical fast transients
(EFT) according to IEC 61000-4-4 of up to ±2 kV.
The THVD1500 provides internal biasing of the receiver input thresholds in combination with large input-
threshold hysteresis. With a positive input threshold of V_IT+ = –50 mV and an input hysteresis of V_HYS = 50 mV,
the receiver output remains logic high under a bus-idle or bus-short conditions without the need for external
failsafe biasing resistors. Device operation is specified over a wide temperature range from –40°C to 125°C.
8.4 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 V_OD = V_A – V_B is positive. When D is low, the output states reverse, B turns high, A becomes low, and V_OD 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 V_CC, thus, when left open while the driver is enabled, output
A turns high and B turns low.
INPUT
D
H
L
X
X
OPEN
ENABLE
DE
H
H
L
OPEN
H
Table 1. Driver Function Table
OUTPUTS
A
B
H
L
L
H
Z
Z
Z
Z
H
L
FUNCTION
Actively drive bus high
Actively drive bus low
Driver disabled
Driver disabled by default
Actively drive bus high by default
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