I know common use of RS485 is top wiring diagram. But in my project we need to use RS485 for extend range and reliability connection but connection will be bottom wiring diagram.
Can I use a single RS485 transceiver IC? Are there any problems with this approach? I'm not sure.
Assuming every device has the same baudrate.
Both of these will work providing you apply the modifications in red: -
Both distant ends of the cable need a suitable termination resistor to protect data reflections causing corruption of the data messages.
Can I use single RS485 transceiver IC ?
The same RS-485 interface IC can be used for master and slaves alike. You can even take the cable interface onto your PCB like this: -
It makes no difference where the master is (middle or end) providing it's using an RS-485 line interface chip. The same interface chip can be used for interfacing the master or the slaves. It makes no difference because RS-485 outputs a current drive signal to the line.
What you propose is the simplest star topology in existence.
RS-485 specifically advises against going for a star topology (mostly due to basically making it ambiguous where termination should be, and there's no "good" answer to that question); but at three full devices on the bus, things might be OK. What you need to realize is that there's 100m of cable between Device 1 and Device 2.
Your devices will have to be able to drive 100m of cable, and you'll need to find the sweet spot between having too little load at each node, and too much load overall in termination to avoid problematic echoes. You're building a frequency-selective channel here. Assuming the E-field change travels at \$\frac23 c_0=2\cdot10^8\frac{\text{m}}{\text{s}}\$, it needs 0.5 µs to travel the from Device 1 to Device 2 (100m), and 0.75 µs to travel back to the Master in the middle if it's reflected at the end. Now, if these 0.75 µs happen to be an odd multiple of half a signal period, you'll have destructive interference there. Uh oh. That means you'll lose signal integrity for some signalling frequencies (including subharmonics introduced through repeating bit patterns), and get amplifications for others. That's why termination is important!
Also: If you have some "collision avoidance" scheme where access to the shared bus can only be asserted when there's been silence for a specific amount of time, then you'll need to account for the travel time when calculating the minimum amount of wait-before-send.
If we are talking about just 2 devices it shouldn't be a problem if you terminate both ends, however, if you use a star architecture (which is essentially what you are doing although with just 2 slaves) with more devices, you will need more terminations, and that will excessively load the driver, the other option is not to put terminations which can screw up the signal due to reflections.
As Marcus says, star architectures in rs485 are specifically advised against, yet in this particular case it should work, whenever you need multiple terminations be sure to calculate the load to not exceed 32 ul, which is the load any rs485 driver should be able to handle
