RS485 transceiver, 3.xV operation

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We use a lot of RS485 in our industrial controller operations.  Most apps use 8-pin SOIC, 5V, Vcc/Gnd/TxD/RxD/TE/~RE/A/B.  They cost about a buck.

 

I'm working on a new board that will use a 3.xV processor.  I thought it would be straightforward to find a corresponding RS485 transceiver that operates on 3V-5V; or failing that at 3.xV.  Yes, I'm finding some, but not many and not for a buck or two.

 

Am I searching incorrectly?  Or any other suggestions?

 

 

You can put lipstick on a pig, but it is still a pig.

I've never met a pig I didn't like, as long as you have some salt and pepper.

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I have design some PCBs for a client with these but not exactly in the price range. (0-70 deg) the SN65 series are a bit more expensive (-40 +85)

 

http://www.digikey.com/product-d...

John Samperi

Ampertronics Pty. Ltd.

www.ampertronics.com.au

* Electronic Design * Custom Products * Contract Assembly

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Exar and intersil have some budget devices.

Note that all RS485 transceivers are not equal! Some will output an idle on an unbiased bus (eg max485) but most will not. This might cause issues with protocols like modbus rtu.

Last Edited: Wed. Aug 12, 2015 - 10:45 PM
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Have just done some searching on exactly this.

 

Maxim has a bunch, of course. But no-where near the $1 cost point. OTOH, most of their recent ones have ESD protected on the 422/485 side. And, they are available in MUCH lower quiescent currents than when I was actively working with them (more than 10 years ago - my how time flies). They do have quite a batch spec'd in the 3.0V to 5.0V span. And, many that have defined states at bus-idle (but not all). Also, choice of slew-rate limiting (could be a plus for FCC/CE emissions). 
 

On the other hand, I have long been very cautious about using Maxim parts after some parts scarcity cycle when they allocated all their parts to big customers, leaving the small guys totally in the lurch. Have never forgotten that.

 

Jim

Jim Wagner Oregon Research Electronics, Consulting Div. Tangent, OR, USA http://www.orelectronics.net

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Look at this at DigiKey (Link).  231 devices in the list.

 

Here is the Intersil ISL83490IBZ (Link).

$1.44 ea @Qty 1 and $0.68 ea @Qty 100.

 

 

Last Edited: Thu. Aug 13, 2015 - 02:22 AM
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I have design some PCBs for a client with these but not exactly in the price range. (0-70 deg) the SN65 series are a bit more expensive (-40 +85)

 

That series is indeed what I found drilling down at DigiKey.  A few bucks.

Exar and intersil have some budget devices.

 

I started poking at Intersil.  They are indeed about a buck!  E.g.

http://www.digikey.com/product-s...

 

Look at this at DigiKey (Link).  231 devices in the list.

 

Here is the Intersil ISL83490IBZ (Link).

$1.44 ea @Qty 1 and $0.68 ea @Qty 100.

Indeed, they are out there. ;)  I must have taken a wrong path in my drill-down.  Certainly now I can find some parts, and proceed with proof-of-concept prototype.  Beyond that I'll work with the hardware designers to see if we want to use a 3.xV or 3V-5V part.

 

 

You can put lipstick on a pig, but it is still a pig.

I've never met a pig I didn't like, as long as you have some salt and pepper.