Altera's APEX True-LVDS Solution
Increases Data Transfer Rate to Industry-Leading 840 Mbps Per Channel
APEXTM 20KE and APEX 20KC devices offer a True-LVDSTM solution making these devices the industry's first system-on-a-programmable-chip (SOPC) solution to support data transfer rates up to 840 Mbps per channel. Altera's True-LVDS solution addresses the high bandwidth demands of communication applications. Figure 1 shows the waveform for the APEX EP20K400E LVDS data channel, toggling at 840 Mbps.
Figure 1. APEX EP20K400E LVDS I/O Performance at 840 Mbps
APEX True-LVDS Solution
The APEX True-LVDS solution not only provides a high data transfer rate of up to 840 Mbps per channel, but also offers high noise immunity, low power consumption, and low electromagnetic interference (EMI) benefits that are utilized by high-speed communication applications. The True-LVDS solution is made possible by the following innovative technology:
- Dedicated receiver and transmitter circuitry performing serial-to-parallel and parallel-to-serial conversions making the high toggle rates (840 Mbps) possible
- On-chip phase-locked loop (PLL) circuitry with 8x multiplication internally boosting the input clock to 840 MHz
- Dedicated deskew circuitry ensuring clock and data signals are internally aligned
- True differential I/O drivers enabling high noise immunity, low power consumption, and low EMI
Figure 2 shows the LVDS receiver and transmitter circuitry.
Figure 2. LVDS Receiver/Transmitter Circuitry
APEX 20KE True-LVDS Performance
When analyzing LVDS I/O performance, it is important to consider various specifications including channel skew on the output pins and the maximum receiver input skew margin. These specifications are required to determine LVDS system performance. The table below defines the specifications and provides the APEX 20KE LVDS values at 840 Mbps.
| Table 1. APEX 20KE True-LVDS Performance |
| Specification |
Definition |
APEX 20KE True-LVDS Values |
| f LVDSDR |
Maximum LVDS data transfer rate |
840 Mbps |
| TCCS |
Transmitter channel-to-channel-skew |
400 ps |
| SW |
Sampling window: required time that data must be stable for the LVDS receiver to capture it |
440 ps |
|
RSKM
|
Receiver input skew margin: allowable board skew, specified with de-skew feature engaged |
473 ps |
APEX True-LVDS Quality
An "eye diagram" is a visual representation of the jitter and output driver quality of an LVDS output signal. It is obtained by sending pseudo-random data over the LVDS channel and using a sampling oscilloscope to perform a persistence measurement. The transitions are captured and plotted over time. Horizontal eye closure is due to jitter, while vertical eye closure is due to signal attenuation or noise. Therefore, a larger "eye" indicates a better quality driver. (For details see the Eye Diagram page.) The "eye diagram" for the APEX EP20K400E device in Figure 3, was measured over 30 minutes in a noisy environment.
Figure 3. LVDS Eye Diagram at 840 Mbps
APEX True-LVDS Applications
The APEX True-LVDS solution is ideal for telecommunication and data communication applications such as switches, hubs, and routers. It is also useful for computing applications such as digital copiers, processor interface, imaging displays, audio and video digital signal processing (DSP), and MPEG stream processing.
The 840 Mbps data transfer rate provides full support for dense wave division multiplexing (DWDM) systems transmitting and receiving OC-12 data with Reed-Solomon forward error correction (FEC) encoding running at 666 Mbps per channel.
APEX LVDS Advantage
APEX devices with LVDS capability provide numerous benefits, including:
- High-frequency performance up to 840 Mbps per channel
- Low power dissipation
- Dedicated built-in LVDS circuitry
- 16 input and output channels
- Built-in data skew reduction circuitry
- Support for 1x, 4x, 7x, or 8x serializer and deserializer
- Low ratio of chip power and ground pins to I/O pins
- Support for multi-drop and point-to-point backplane architecture interfaces
- Support data transfer across cable and connectors
With the True-LVDS solution, APEX devices offer the highest performance, highest bandwidth, lowest power, SOPC solution for high-speed data transmission designs.
Related Links
|
Literature
> 
