LVDS vs TTL

LVDS and TTL are two common names for signaling that are quite common nowadays. “TTL” stands for “Transistor-Transistor Logic” but usually is used to refer to TTL compatible signaling. On the other hand, “LVDS” stands for “Low Voltage Differential Signaling,” and is a rather accurate description of the manner that it transmits information. This is also the main difference between LVDS and TTL. LVDS uses two wires with the voltage difference between the two determining whether it’s a “0”or a “1.” In contrast, TTL uses the presence or absence of a voltage with respect to a ground to indicate a “1” and a “0” respectively.

The voltage level that TTL uses is based on the supply that the transistor uses. Over time, this has become standardized to about five volts. This is much higher compared to the roughly 350mV used by LVDS. Thus, LVDS consumes much less power than TTL.

Another advantage that LVDS has is its inherent resistance to interference. One contributing factor is the use of twisted pairs which creates a tight electromagnetic field coupling. Even with voltage spikes, the wires will experience the same so the differential voltage will still be the same. With TTL, a voltage spike while transmitting a “0” may erroneously result in a “1” at the receiver.

In ordinary devices, there are also a couple of differences between those that use LVDS and those that use TTL. Devices that use LVDS are able to utilize longer wires due in part to its resistance to interference. This is beneficial if the devices you are connecting are not very close to each other as you will probably not need to use a repeater. Another difference is the number of wires needed. Devices that use TTL often transmit information in parallel. This requires a considerable number of wires as each signal requires a separate wire. Because LVDS is serial and congregates multiple signals into one stream, it uses fewer wires than what TTL needs.

Although LVDS and TTL are different signaling methods, there are special circuits that are able to convert one to the other. These are used in order to connect an LVDS device to a TTL device.

Summary:

1.TTL uses ground as reference while LVDS doesn’t.
2.LVDS can use lower voltage levels than TTL.
3.LVDS is a lot more resistant to interference than TTL.
4.Devices that use LVDS can have longer wires than devices that use TTL.
5.Devices that use LVDS typically have fewer wires than devices that use TTL.
6.LVDS and TTL are not compatible but can be converted.

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