The advantages of differential signaling and its positive impact on high-speed designs

With differential signals, the rise and fall times are generally shorter than single-ended signals. Therefore, data rates above 10 Gbps have become an achievable standard in current communication systems. A smaller signal swing can reduce the overall power budget of the system. LVPECL and CML differential signals have a higher output voltage swing, so the power consumption is slightly higher than that of LVDS and M-LVDS signals.

In this article, we will explore the advantages of differential signaling and how these advantages can have a positive impact ON your high-speed design.

Single-ended signals such as TTL, CMOS and their lower Voltage counterparts such as LVTTL and LVCMOS are common techniques in digital circuit design. However, the use of these types of signal transmission techniques has some shortcomings, which will ultimately limit high-speed designs. Due to different ground potentials and high slew rates, single-ended signals are very difficult to operate in long-distance communications. A single-ended driver that switches between positive and negative rails for each signal requires a high ΔV/Δt, which means that you need a variety of load currents (I = CΔV/Δt). Therefore, the limitations of rail-to-rail signals (large ΔV) are obvious: more power is needed to achieve a shorter conversion time (smaller Δt). So how do we get high-speed signals around digital design and avoid the loss of single-ended signals? Implement differential signaling!

Differential systems are generally three-wire systems (and possibly more), including non-inverted signals, inverted signals, and ground references. In an ideal differential system, V+ = -V- and |I+| = |I-| can produce balanced signals. In a balanced differential topology, the two wires are tightly coupled together, and the net ground current (IGND) is equal to zero. Implementing a differential signal topology in a system has various advantages, including higher signal transmission rates, high common-mode noise immunity, and lower power consumption.

With differential signals, the rise and fall times are generally shorter than single-ended signals. Therefore, data rates above 10 Gbps have become an achievable standard in current communication systems. A smaller signal swing can reduce the overall power budget of the system. LVPECL and CML differential signals have a higher output voltage swing, so the power consumption is slightly higher than that of LVDS and M-LVDS signals.

The second advantage of differential signal transmission is the immunity to common mode noise. Since the differential signal is composed of positive and negative signals of equal amplitude and opposite polarity, any common mode noise coupled to the transmission signal will be canceled by its interrogation. This is definitely a huge system advantage, because there are likely to be some switching regulators connected to the power and ground panels, which are just waiting to couple their energy to your clean signal. This may not seem like a big deal at first, but you will soon find that when a strict jitter budget is critical to a design, every picosecond is critical!

The following table is a summary of the most common differential signal topologies, which vary depending on power consumption, performance, and application areas:

The advantages of differential signaling and its positive impact on high-speed designs

An excellent example of a differential signal application is to connect a single-ended VCO output to an FPGA or serial deserializer that requires a differential LVDS clock input. To avoid meeting this requirement and destroying the already stable system clock architecture, you can implement a device (such as the SN65LVDS1 single-channel VDS transmitter, etc.) to perform single-ended to differential signal conversion between the VCO and the terminal device. SN65LVDS1 operates with a power supply voltage of 2.4V or higher, which is ideal for low-power applications without a 3.3V power rail.

In this article, we will explore the advantages of differential signaling and how these advantages can have a positive impact on your high-speed design.

Single-ended signals such as TTL, CMOS and their lower voltage counterparts such as LVTTL and LVCMOS are common techniques in digital circuit design. However, the use of these types of signal transmission techniques has some shortcomings, which will ultimately limit high-speed designs. Due to different ground potentials and high slew rates, single-ended signals are very difficult to operate in long-distance communications. A single-ended driver that switches between the positive and negative rails for each signal requires a high ΔV/Δt, which means that you need a variety of load currents (I = CΔV/Δt). Therefore, the limitations of rail-to-rail signals (large ΔV) are obvious: more power is required to achieve a shorter conversion time (smaller Δt). So how do we get high-speed signals around digital design and avoid the loss of single-ended signals? Implement differential signaling!

Differential systems are generally three-wire systems (and possibly more), including non-inverted signals, inverted signals, and ground references. In an ideal differential system, V+ = -V- and |I+| = |I-| can produce balanced signals. In a balanced differential topology, the two wires are tightly coupled together, and the net ground current (IGND) is equal to zero. Implementing a differential signal topology in a system has various advantages, including higher signal transmission rates, high common-mode noise immunity, and lower power consumption.

With differential signals, the rise and fall times are generally shorter than single-ended signals. Therefore, data rates above 10 Gbps have become an achievable standard in current communication systems. A smaller signal swing can reduce the overall power budget of the system. LVPECL and CML differential signals have a higher output voltage swing, so the power consumption is slightly higher than that of LVDS and M-LVDS signals.

The second advantage of differential signal transmission is the immunity to common mode noise. Since the differential signal is composed of positive and negative signals of equal amplitude and opposite polarity, any common-mode noise coupled to the transmission signal will be cancelled out by its interrogation. This is definitely a huge system advantage, because there are likely to be some switching regulators connected to the power and ground panels, which are just waiting to couple their energy to your clean signal. This may seem trivial at first, but you will soon find that when a strict jitter budget is critical to a design, every picosecond is critical!

The following table is a summary of the most common differential signal topologies, which vary depending on power consumption, performance, and application areas:

The advantages of differential signaling and its positive impact on high-speed designs

An excellent example of a differential signal application is to connect a single-ended VCO output to an FPGA or serial deserializer that requires a differential LVDS clock input. To avoid meeting this requirement and destroying the already stable system clock architecture, you can implement a device (such as the SN65LVDS1 single-channel VDS transmitter, etc.) to perform single-ended to differential signal conversion between the VCO and the terminal device. SN65LVDS1 operates with a power supply voltage of 2.4V or higher, which is ideal for low-power applications without a 3.3V power rail.

The Links:   AT070TN07-V2 https://www.slw-ele.com/lq150x1lgn2e.html“> LQ150X1LGN2E