AM26C31: fault protection meaning in AM26C31 and other RS3485 transceivers

Zoe Yang

Part Number: AM26C31
Other Parts Discussed in Thread: AM26LV31, AM26LS31, SN75LBC172, AM26LS31M,

Hello dear:

I have a question about the features of RS485 transceivers. There is a character named FAULT PROTECTION. But I can't find the working principle corresponding to this item in the data sheet. Can anyone help to explain to me how does it mean? And the comparison data on it between AM26C31 AND AM26LV31?

over 3 years ago

0 Clemens Ladisch over 3 years ago

Guru 316510 points

The common-mode range specifies the bus voltages with which the device will work correctly. This should be specified in the recommended operating conditions table.

The fault-protection range specifies the bus voltages with which the device will not be damaged. This should be specified in the absolute maximum ratings table.

It appears that the datasheets for these devices call this value "differential input voltage"; this name does not make sense for a driver.

0 Zoe Yang over 3 years ago in reply to Clemens Ladisch

TI__Intellectual 2210 points

Thanks Clemens for your reply! I do notice the Vid character defined in AM26C31 data sheet ranging from -14V to 14V. But in other transceivers I could not find the parameter anymore, Which referring to my last question fault protection is ranging from -7V to 7V. My client has some questions on the definition of this character. He is looking for a compatible device compared with AM26LS31. And there is no definition of this Vid in it. Could you give more advice on this point? Thanks again!

0 Clemens Ladisch over 3 years ago in reply to Zoe Yang

Guru 316510 points

Devices like the AM26C31 or SN75LBC172 are compatible. What is the problem with the AM26LS31?

I cannot give more information about those devices; I do not know more than is written in the datasheet.

0 Hao L over 3 years ago in reply to Clemens Ladisch

TI__Mastermind 25705 points

Zoe,

Like Clemens said, the Vid of AM26C31 is not valid. This device is a quad line driver, whose input is TTL logic not RS-485. Therefore the input should not be specified with any common mode.

Clemens' comments about the fault voltage are correct and accurate.

0 Zoe Yang over 3 years ago in reply to Hao L

TI__Intellectual 2210 points

Thanks Hao! So can I use AM26c31 as Rs-485 transmitter? Client on my side was asking a replacement of AM26LS31, They want a device which is industrial grade. As far as I know AM26LS31 is commercial grade.

0 Zoe Yang over 3 years ago in reply to Clemens Ladisch

TI__Intellectual 2210 points

Clemens, the clients on my side want to replace AM26LS31 to industrial-grade one. SO is it compatible between these two devices,AM26LS31 and AM26C31?

0 Hao L over 3 years ago in reply to Zoe Yang

TI__Mastermind 25705 points

Yes, AM26C31 can be applied as the RS-485 transmitter, which can be the replacement of AM26LS31. I'm not sure what you meant by industrial grade. Are there any specific requirement?