Will ST485CDR/ ST485BDR work at 3.3V Vcc Supply

[DBhut.1]

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[Peter BENSCH]

The ST485CDR and ST485BDR work only with 5V supply.

For 3.3V supply you could use e.g. the pin compatible ST3485ECDR/ST3485EBDR.

Does it answer your question?

Regards

/Peter

[DBhut.1]

We have used 30 qty of ST485CDR on 3.3 V Product and all are working fine since last 6 months, and recently we found that, it will work on 5V, So Will there be any issue in performance, or any thing else?

Due to non availability or longer lead time of ST3485ECDR/ST3485EBDR, we have to use ST485CDR for our next product at 3.3V. Should we use it, or suggest any other alternative which is easily available in market.

[Peter BENSCH]

The function of ST485B and ST485C is only guaranteed when operating at 5V±5%, at 3.3V they operate out of specification and STMicroelectronics can no longer guarantee proper function. The possible effects are unpredictable and may (but need not) include anything up to complete failure.

Regards

/Peter

[DBhut.1]

Hello @Peter BENSCH​ 

what's the difference between ST485CDR at 5V and  ST3485ECDR at 3.3V in terms of Performance, communication distance(range), reliability, data fault tolerance, no of device working on same bus, etc.

Thank You

[Peter BENSCH]

Well, you can find all the information on this in the data sheets and in the description of RS-485, e.g. in Wikipedia.

The number of bus participants is determined, for example, by the input resistance of the receiver, which is 24k for both types, so that a maximum of 64 participants is typically assumed (receivers with 6k, for example, only allow 16 participants).

The range is determined less by the supply voltage than by the transmission rate, since RS-485 uses differential signalling.

For further and deeper technical discussions, it may be advisable to contact your local distributor.

Regards

/Peter

[sreejithrnair]

Hi @Peter BENSCH ,

Could you kindly confirm whether the ST RS 485 transceiver part ST485EBDR is compatible with 3.3V?

 

 

Regards,
Sreejith

[Peter BENSCH]

@sreejithrnair If you mean the supply voltage with your question "compatible with 3.3V", then the ST485EB data sheet clearly states on page 1: "It operates from a single 5 V supply". Otherwise, the above also applies here.

Regards
/Peter