Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Line Driver with 3-STATE Outputs

Status
Not open for further replies.

Imanuel Shalti Ayele

Newbie level 2
Joined
Nov 12, 2014
Messages
2
Helped
0
Reputation
0
Reaction score
0
Trophy points
1
Activity points
21
Hi guys,

I'm new here and want to be a pro in board design..(need alot of job for that)
I need something to understand here, did I need to put a pull-up/down resistors to this line driver inputs? and maybe 33R serial resistor for termination?

https://www.fairchildsemi.com/datasheets/74/74AC244.pdf

I need to work with RS-422 and want to split 1 input to 4 output with this driver.
Somebody have another idea for that?

Thx thx!!!
 

aruipksni

Full Member level 6
Joined
May 23, 2013
Messages
346
Helped
68
Reputation
136
Reaction score
66
Trophy points
1,308
Activity points
3,004
you need to have a rs422 transciver - this buffer is not suitable.
 
Last edited:

D.A.(Tony)Stewart

Advanced Member level 5
Joined
Sep 26, 2007
Messages
7,061
Helped
1,721
Reputation
3,441
Reaction score
1,720
Trophy points
1,413
Location
Richmond Hill, ON, Canada
Activity points
51,829
Read the design guidelines

https://focus.ti.com/lit/an/slla070d/slla070d.pdf

RS-485 compliant drivers can be used for Rs-422 multidrop with one driver.

THe termination resistors at each end of the bus match the differential impedance of the pair with active terminators ( ie. pull up/down or series to Vth
 

Imanuel Shalti Ayele

Newbie level 2
Joined
Nov 12, 2014
Messages
2
Helped
0
Reputation
0
Reaction score
0
Trophy points
1
Activity points
21
Hi guys and thanks!
I forget to mention that i've got a diff. Tx & Rx from outside world(host,PLC etc.) and this 4 wires get into a MAX3490 transceiver.
https://www.sos.sk/a_info/resource/c/max/MAX3485CPA+.pdf

The two lines regarding the transceiver output, one of them i need to split 1 to 4(Tx), and the other one i need to merge 4 to 1(Rx).
I did it with the line driver i mention yesterday.


Thank u again guys!!!!
 

FvM

Super Moderator
Staff member
Joined
Jan 22, 2008
Messages
49,418
Helped
14,441
Reputation
29,146
Reaction score
13,239
Trophy points
1,393
Location
Bochum, Germany
Activity points
284,384
To avoid talking on cross purposes, you better sketch the intended connection of RS-422 transceiver, 3-state driver and lines.
 

dick_freebird

Advanced Member level 5
Joined
Mar 4, 2008
Messages
7,570
Helped
2,186
Reputation
4,378
Reaction score
2,080
Trophy points
1,393
Location
USA
Activity points
60,487
If you pin one of the RS422 inputs to midrail then the receiver
will "work" with a single ended input. Not to expected specs.
And you'd then probably lose the input failsafe function if that
matters, unless the "live" output is also pulled to that center
point.

You could throw true and complement out the '244 outputs
using two of the available channels, plus a preceding inversion
somewhere for one. Keep the 100 ohms cross-output termination.
Then the only thing you lose is the reverse current protection
(cold sparing etc. is compromised).
 
Status
Not open for further replies.

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top