THVD1551DGKR Interface IC

THVD1551DGKR Description

The THVD15xx range of noise-immune RS-485/RS-422 transceivers is designed to function in harsh industrial settings. The bus pins on these devices are protected against ESD and fast electrical transients (EFT) per the IEC. No more protection mechanisms at the system level are necessary.

One supply of 5 V is required to operate any of these devices. These devices belong to a family that has a broad common-mode voltage range, which qualifies them for use in multi-point applications even when the cable runs are very long.

Applications with limited space can use the THVD15xx family of devices because they are offered in compact VSSOP packages. These devices are characterized throughout a temperature range of –40 to 125 degrees Celsius while exposed to ambient free-air temperatures.

Features for the THVD1551

• meets or exceeds the TIA/EIA-485A Standard’s requirements.
• Supply voltage of 4.5 to 5.5 volts.
• Protection for the integrated bus I/O.
• 30 kV HBM ESD is -.

-± 18 kV ESD Contact Discharge, IEC 61000-4-2.

IEC 61000-4-2 ESD Air-Gap Discharge at 25 kV.

-± 4 kV Electrical Fast Transient, IEC 61000-4-4.

• Operational Common-mode in Extended: 15 V.
• 500 kbps and 50 Mbps Data Rates with Low EMI.
• Longer Temperature Range: -40 to 125 degrees Celsius.
• For noise rejection, a large receiver hysteresis is used.
• Power usage is minimal.
• 1 A is the low standby supply current.

– Operating Current: 1 mA.

• Glitch-Free Power-Up/Down for the Ability to Plug in Hot.
• A Short, Idle, and Open Bus Failsafe.
• Options for 1/8-unit loads (Up to 256 Bus Nodes).
• Compact VSSOP Packages For drop-in compatibility, save board space or SOIC.

Detailed Description

Overview Both the THVD1510 and the THVD1550 are low-power, half-duplex RS-485 transceivers. They are offered in two different speed categories, each appropriate for transferring data at up to 500 kbps or 50 Mbps, respectively. The THVD1551 does not require additional external enabling pins as it is already fully activated. The THVD1512 and THVD1552 have driver enables set to active-high, while the receiver enables are set to active-low. By turning off the driver and the receiver, it is possible to reduce the current drawn by the device to less than one microampere.

Feature Description

Internal ESD protection circuits protect the THVD15xx transceivers from electrostatic discharges (ESD) in accordance with IEC 61000-4-2 up to 18 kV and from fast electrical transients (EFT) in accordance with IEC 61000-4-4 up to 4 kV. These protection levels are in accordance with the International Electrotechnical Commission’s 61000-4-2 and 61000-4-4 standards, respectively. These standards adhere to the criteria in the IEC 61000-4-2 and the IEC 61000-4-4 documents, respectively. One can satisfice the 4 kV EFT Criterion A if the system architecture has been thoughtfully considered (no data loss when transient noise is present).

The THVD15xx device family offers internal biasing of the receiver input thresholds and a large amount of input threshold hysteresis. External failsafe biasing resistors are not required because the receiver output maintains its logic high state regardless of whether the bus is idle or shorted. The functionality of the device is characterized by being able to operate in a broad temperature range, ranging from -40 degrees Celsius to 125 degrees Celsius.

Device Functional Modes

The THVD1510 and THVD1550 have their unique set of functional device modes. When the driver enables pin DE to be set to the logic high position, the differential outputs A and B will follow the logic states of the data input, D. When the logic level at D is high, it forces A and B to switch places, making them both high. In this particular scenario, the differential output voltage, which may be written as VOD = VA – VB, has a positive value. When D is not high, the output states are inverted, with B becoming high, A becoming low, and VOD becoming negative.

When DE is at a low level, both outputs will change into a high-impedance state. Under these circumstances, the logical state at D is completely immaterial. Because the DE pin incorporates an inbuilt pull-down resistor that connects to the ground, the driver will be deactivated (high-impedance) by default if this pin is left open. Because the D pin contains an internal pull-up resistor connected to VCC, when the driver is enabled, and the D pin is left open, the output A becomes high while output B becomes low.

Application and Implementation

● Application Information

Half-duplex and full-duplex RS-485 transceivers are typically utilized for asynchronous data transmissions. These transceivers are included in the THVD15xx family of products. The driver enables pins, and the receiver enables pins on half-duplex devices, making it possible to configure various alternative operating modes. The implementation of full duplex communication calls for two signal pairs (four wires), enabling each node to send data over one pair of wires while simultaneously receiving data over the other pair of wires.

● Design Requirements

RS-485 is a strong electrical standard that is suited for long-distance networking. It can be used in various applications with various requirements, such as the distance between nodes, the data rate, and the number of nodes.

● Receiver Failsafe

The differential receivers that make up the THVD15xx series are designed to be failsafe in the event of invalid bus states brought on by the following factors:

• Conditions of an open bus, such as a connector, have become disconnected.
• Situations that cause the bus to be shorted, such as damage to the cables that causes the twisted pair to become connected.
• Idle bus conditions are those that take place aboard a bus when there is no driver actively operating the vehicle.

In any of these circumstances, the differential receiver will provide an output of a failsafe logic high state to ensure that the receiver’s output is not ambiguous. Receivers can be made failsafe by shifting the thresholds of the receivers in such a way that the indeterminate input range does not contain zero volts differential. To comply with the RS-422 and RS-485 standards, the receiver output must produce a high when the differential input VID is greater than 200 mV in a positive direction, and it must output a low when the VID is greater than –200 mV in a negative direction. The failsafe mechanism’s performance depends on three-receiver parameters: VTH+, VTH–, and VHYS (the distance that separates VTH+ and VTH–).

Conclusion

Each supply should have a 100 nF ceramic capacitor isolated from it and placed as close to the supply pins as possible. This will ensure that the device will operate reliably regardless of the data rate or supply voltage. This helps to compensate for the resistance and inductance of the PCB power planes, along with lowering the ripple voltage found on the outputs of switched-mode power sources.

If you need additional information or wish to order THVD1551DGKR, you’ve come to the correct place. Give us a call at ICRFQ, your leading electronic distributor in China, and we will ensure you receive the best goods at a reasonable price.

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