ISO1430DWR datasheet(25/49 Pages) TI2

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9.3 Feature Description

9.3.1 Electromagnetic Compatibility (EMC) Considerations

Many applications in harsh industrial environment are sensitive to disturbances such as electrostatic discharge

(ESD), electrical fast transient (EFT), surge and electromagnetic emissions. These electromagnetic disturbances

are regulated by international standards such as IEC 61000-4-x and CISPR 22. Although system-level

performance and reliability depends, to a large extent, on the application board design and layout, the ISO14xx

devices incorporate dedicated circuitry to protect the transceiver from ±16 kV ESD per IEC61000-4-2 and ±4 kV

EFT per IEC 61000-4-4. System designers can achieve the ±4-kV EFT Criterion A with careful system design

(data communication between nodes in the presence of transient noise with minimum to no data loss).

9.3.2 Failsafe Receiver

The differential receiver of the ISO14xx devices has failsafe protection from invalid bus states caused by:

• Open bus conditions such as a broken cable or a disconnected connector

• Shorted bus conditions such as insulation breakdown of a cable that shorts the twisted-pair

• Idle bus conditions that occur when no driver on the bus is actively driving

The differential input of the RS-485 receiver is 0 in any of these conditions for a terminated transmission line.

The receiver outputs a failsafe logic-high state so that the output of the receiver is not indeterminate.

The receiver thresholds are offset in the receiver failsafe protection so that the indeterminate range of the does

not include a 0 V differential. The receiver output must generate a logic high when the differential input (VID)

is greater than 200 mV to comply with the RS-485 standard. The receiver output must also generate a output

a logic low when VID is less than –200 mV to comply with the RS-485 standard. The receiver parameters that

determine the failsafe performance are VTH+, VTH–, and VHYS. Differential signals less than –200 mV always

cause a low receiver output as shown in the Electrical Characteristics table. Differential signals greater than 200

mV always cause a high receiver output. A differential input signal that is near zero is still greater than the VTH+

threshold which makes the receiver output logic high. The receiver output goes to a low state only when the

differential input decreases by VHYS to less than VTH+.

The internal failsafe biasing feature removes the need for the two external resistors that are typically required

with traditional isolated RS-485 transceivers as shown in Figure 9-3.

VCC1

GND1

GND2

VCC2

Galvanic

Isolation Barrier

VCC2

RS-485

Bus

Traditional

transceiver

ISO

Ground

VCC1

GND1

GND2

VCC2

Galvanic

Isolation Barrier

VCC2

RS-485

Bus

ISO1410

(R1 and R2 not needed)

ISO

Ground

Figure 9-3. Failsafe Transceiver

9.3.3 Thermal Shutdown

The ISO14xx devices have a thermal shutdown circuit to protect against damage when a fault condition occurs.

A driver output short circuit or bus contention condition can cause the driver current to increase significantly

which increases the power dissipation inside the device. An increase in the die temperature is monitored and

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ISO1450, ISO1452, ISO1410, ISO1412, ISO1430, ISO1432

SLLSF22H – APRIL 2018 – REVISED JUNE 2024

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