提供3.3V电压的RS485收发器.我可以接收什么电压电平? [英] RS485 transceiver supplied with 3.3V. What voltage levels can I receive?

问题描述

我正在使用 LTC2854 收发器.我不知道它将处于何种情况.所以我不知道其他设备将在什么电压水平上进行通信.我将为收发器提供3.3V电压，并在0V和+ 3.3V电压下进行通信.

I'm designing a print for RS485 with the LTC2854 transceiver. I don't know what situation it will be placed in. So I don't know what voltage levels the other devices will communicate on. I will supply the transceiver with 3.3V and communicate on 0V and +3.3V.

这是否意味着我仍然可以接收总线上其他设备的-7V-+ 12V的整个电压范围?还是这意味着它只能在0V-+ 3.3V电平系统上实现?

Does this mean I can still receive the full range of voltages -7V - +12V of other devices on the bus? Or does this mean that it can only be implemented on 0V - +3.3V level systems?

根据我的理解，只要收发器的a-b差至少为+/- 200mV，我就应该能够检测到零与一之间的差.我不会使用偏置，并且可以使用LTC2854打开或关闭终端电阻.您能解释一下我的理解是否正确吗?

In my understanding I should be able to detect difference between a zero and one, as long as the difference a-b of the transceiver is at least +/- 200mV. I won't be using biasing and the termination resistor can be turned on or off with LTC2854. Could you explain if my understanding is correct?

推荐答案

您的理解是正确的.

当总线上的所有设备都符合RS485标准时，您不必担心电压(在收发器的RS485侧).您的设备将能够与任何其他RS485兼容设备进行通话.

When all devices on your bus comply with the RS485 standard you don't have to worry about voltages (on the RS485 side of the transceiver). Your device will be able to talk to any other RS485-compatible device.

要进一步详细说明:请注意，任何收发器都充当一种转换器，它将一侧的电子层转换为另一侧.例如，在您的情况下，一侧有3.3V逻辑，另一侧有RS485.收发器负责将单侧3.3V逻辑转换为RS485总线所需的差分电平.

To elaborate a bit more: note that any transceiver acts as a kind of translator, it converts the electrical layer on one side to the other. For instance, in your case, you have 3.3V logic on one side and RS485 on the other. The transceiver takes care of converting the single-side 3.3V logic to the differential levels required by the RS485 bus.

您将无法使用相同的LTC2854将TTL 5V逻辑设备连接到RS485.为此，您需要一个不同的收发器，例如， LTM2881-5 .

What you would not be able to do is use the same LTC2854 to interface a TTL 5V logic device to RS485. To do that you need a different transceiver, for instance, a LTM2881-5.

上面提到的一般R485通用兼容性有些细微差别，例如总线偏置或阻抗(与终端电阻有关)有时可能会出现错误(大多数情况下，当您必须覆盖很长的距离或处于嘈杂的工业环境中时)头疼，但只要有足够的时间，耐心和巧思，您就应该能够解决这些问题.

There are some nuances to the general R485 universal compatibility stated above, like bus biasing or impedance (related to the terminating resistors) that can be sometimes (mostly when you have to cover long distances or you are in a noisy industrial environment) a headache but you should always be able to solve those given enough time, patience and ingenuity.

这篇关于提供3.3V电压的RS485收发器.我可以接收什么电压电平?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！