THVD1420: reference schematic for RS422

A single half-duplex transceiver is usually not used for bidirectional RS-422; you'd need separate devices for TX and RX. (In that case, DE and /RE would be always high or always low.)

Hi Clemens,

Let me modify my question.
Is it possible replace like below? 

Also, It is helpful if there is reference design for using THVD1420 as RS422. 

Best regards,

Goto

Your current system has eight unidirectional channels. Using the THVD1420 with the same signals would require eight chips in the module (four configured to always transmit, and four to always receive).

With full-duplex transceivers like the THVD1451, you would need only four chips.

Why do you want to replace the AM26LV31/DS26LV32AT?

Replace is because of reducing channels.
Actually, two drivers and one receiver are need, so I consider use three THVD1420s.
Also, system to be connected are different and half-duplex is enough.

Thank you.

Goto

Customer now uses half duplex AM26LV31 and DS26LV32 for RS422. This is not bidirectional.
Channel is reduced  and they would like replace device with minimum system change.
So, THVD1420 is selected.

Is this mistake?   

"Half duplex" means that the drivers and receivers are connected to the same bus lines, and that all modules control the driver enable signals so that at most one driver on the bus is active at the same time.

This is possible with the THVD1420.

Customer now considering design.

They seek reference design.
The constant in D/S and in RS-485 Half-Duplex EVM User's Guide are diffrent.

When usage is for RS-422, which design is better for referenece?

Best regards,
Goto

Those 50 Ω resistors are suitable only for a signal generator with a 50 Ω output; do not use them in a real circuit. The EVM is not a good example.

What protection components to use depends on what noise you expect on the bus. What components did the old design use? Are the reasons still known?