Current consumption for RS485 transceivers?

Question

I am building a prototype that uses a RS485 BUS to communicate many devices and current consumption is a crucial part in this project. In order to set the communication up, I have been looking at several manufacturers. However, I haven't been able to find the current consumption while sending or receiving data in the datasheet specifications of any of the products. I also didn't find a graphic showing Icc(mA) vs. Datarate(Mbps) like i found in some other Maxim Integrated products. Do you know where is this information available?

This is an example of the table i was talking about.

In particular, I have identified the following products to be valid for my solution:

• Analog Devices:

  • ADM485E
  • ADM1487E
  • ADM3486E
  • ADM4852
• Texas Instruments:
  • DS1487
  • DS481
  • SN65HVD3085E
  • DS485
• Maxim Integrated:
  • MAX1487
  • MAX1487E
  • MAX485
  • MAX485E
  • MAX481
  • MAX481E

Thank you in advance.

Edit: First of all, thanks for your answers and comments.

As some of you have answered, the current consumption could be negligible in most cases due to the short ammount of time the transceiver is transmitting. In my case I have to send images and it takes roughly 2.5 seconds for every image sensor on the bus, which in total takes up about 14.4 % of the total time, thus not beeing negligible.

Most of you have poined out the average powed dissipation section on the datasheets of the transceivers, so I will look into that for the devices I have asked for and post here the results I come up with.

Answer 1

Did you estimate the proportion of time your system will actually be transmitting data? In most applications, this is very small, proabably less than 1%. Most of the time, transceivers are just idle. That is why it isn't really specified, because it doesn't account for much in the total power consumption.

Also note that I saw it is actually specified for SN65HVD3085E in the datasheet: there is a line in chapter 6.7: P(avg) mentioning 205mW max when transmitting "a 50% duty cycle square wave at max specified signal rate". This makes about 40mA, which is a lot compared to the idle consumption, but, once again, when multiplied by the proportion of time you actually have to transmit data, certainly become negligible.

I didn't check the datasheets of all other transceivers you're referencing, but I saw it was indeed unmentioned on a few others. Anyway, it most certainly is in the same range, and seems to be in check with the graph you provided in your question, too.

In short: if you need to conserve power, you should focus on the protocol so you transmit a minimum amount of data, and only when absolutely necessary (avoid polling at frequent intervals). This is your best bet.