I need to design repeater for RS 485 with speed up to 1.5 Mbps.
My application is to just boost/amplify the data signal coming from master device to slave.

Here are some details about the data bus:
Communication rate : 1.5 Mbps data rate using Manchester II encoding.

Can you suggest the design for repeater circuit using Texas RS 485 Transreceiver-SN65HVD3082E?
If not SN65HVD3082E IC, Can you suggest some different RS 485 high speed trans receiver designs too?

Thanks alot.

 

Please provide us with more information.

1. What kind of cable are you using?
2. How long is your cable?
3. Is this single ended termination between two devices or are there any stubs along the cable?
4. Is this half duplex or full duplex RS-485?

 

"... The SN65HVD3082E device is optimized for signaling rates up to 200 kbps ..."
You need 1.5 Mbps ?

An EXAMPLE Repeater - ONLY 100 Kbps - Dual Isolated Half-Duplex RS-485 Repeater
http://www.ti.com/lit/ug/tidu590/tidu590.pdf

Isolated RS-485 Repeater with Automatic Direction Control
https://www.analog.com/media/en/technical-documentation/application-notes/AN-1458.pdf

How Far and How Fast Can You Go with RS-485?
https://www.maximintegrated.com/en/app-notes/index.mvp/id/3884

 

Please provide us with more information.

1. What kind of cable are you using?
2. How long is your cable?
3. Is this single ended termination between two devices or are there any stubs along the cable?
4. Is this half duplex or full duplex RS-485?

Thank you for your reply
Here is the information you need
Ans:
1. I am using shielded cable.
2. In my application the distance between master and slave will be quite long(Around 20 to 30m). And i require repeater irrespective of distance between master and slave.
3. No single ended termination or stub along the cable,
there is termination at both the ends(master and slave) as shown in picture attached


Thank you.

 

"... The SN65HVD3082E device is optimized for signaling rates up to 200 kbps ..."
You need 1.5 Mbps ?

An EXAMPLE Repeater - ONLY 100 Kbps - Dual Isolated Half-Duplex RS-485 Repeater
http://www.ti.com/lit/ug/tidu590/tidu590.pdf

Isolated RS-485 Repeater with Automatic Direction Control
https://www.analog.com/media/en/technical-documentation/application-notes/AN-1458.pdf

How Far and How Fast Can You Go with RS-485?
https://www.maximintegrated.com/en/app-notes/index.mvp/id/3884

Thank you pointing that out, i will instead use SN65HVD3088E.

Also can you help me with the schematic layout for the same?
Referring to the schematic of Isolated RS-485 repeater with Automatic Direction Control, Will this schematic work for every bus which is based on RS 485 logical levels? For example: Profibus, MVB(Multi-Function Vehicle Bus)?
Can you let me know the differences if any required for designing for different buses based on RS 485 logical levels?

Thank you

 

1. I am using shielded cable.
2. In my application the distance between master and slave will be quite long(Around 20 to 30m). And i require repeater irrespective of distance between master and slave.
3. No single ended termination or stub along the cable,
there is termination at both the ends(master and slave) as shown in picture attached.

1) We need more information than that. What is the product number of the cable? What is the characteristic impedance? Is it twisted pair? How many pairs?

2) For 30m at 1.5Mbps you should not need a repeater.

3) Your diagram shows stubs off the line which makes repeater implementation more difficult.
Also you need termination at both ends but DC bias at one end. I would select higher Ru and Rd values.

4) Full duplex repeater on single pair is going to be more difficult. I would go either one-way half duplex on one pair or two pair full duplex. However, see answer (2).

 

I agree with MrChips.
30M should be ok without a repeater. RS485 is good for 1KM or more so 30M is a short run.
More importantly, at those speeds, is to have good quality cable of the correct impedance and a correctly terminated network to avoid reflections.