AN-330: 77V1264 PHY, Cable Length & Jitter Guide



Category: Telephone, cellular phone and intercom
Manufacture: Integrated Device Technology, Inc.
Datasheet: Download this application note


Description:
Transmission Distance and Jitter Guide
IDT77V1264L200 Application Note AN-330
September 27, 2001: Initial publication.
Cable Length Guide for the 77V1264L200 Over view
The purpose of this document is to demonstrate the signal quality of TX and RX signals over 10m of UTP5 cable when using the IDT77v1264L200 ATM PHY. For comparison purposes, results of some simulations done with 10m of RG174 coax cable are also shown. Signal quality simulations for 1.5m of traces on an FR4 material PCB, including connectors, are shown for backplane applications.
Several tests were run over 10m of UTP5 cable where one port of the 77v1264L200 transmitted or received data to / from another 77v1264L200 ATM PHY. The BER test was run for extended periods of times (up to 72 hours). No Bit errors were seen and the signals showed a clean open eye diagram. Simulations were done for RG174 cable and showed clean eye opening waveforms. Simulations for backplane applications, where signals are expected to run through approximately 1.5 meters of trace length and through connectors, also showed clean eye opening waveforms.
These tests were performed to verify that no bit errors are seen for all line rates that the IDT77V1264L200 ATM PHY is recommended for. At the time this document is written, the ATM forum specifies that BER should not exceed 1E-10 at data rates of 25.6Mbps. There is no specification for higher data rates.
An ATM generator / analyzer (Adtech) was used as the data source. The maximum data output of this generator is limited to 150Mbps. The data rate was adjusted based on the multiplier set in the Enhanced control register 2 of the IDT77V1264L200. In order to separate the data between different ports of the PHY, different VCIs were sent to each port. Two SwitchStar motherboards were used -- each with a separate 77v1264L200 line card.
2001 Integrated Device Technology, Inc.
IDT77V1264L200 Application Note AN-330
Through 10m UTP5 cable Figure 1 Configuration for Bit Error rate tests
In the above configuration, only one port was active when the line rate was 256Mbps. For 32Mbps and 64Mbps, more than one port was active. Using the same configuration, different lengths of UTP5 cable ranging from 1m to 10m were used. Refer to signal quality and jitter measured in the next section.
Bit Error Rate Test Results
The 256Mbps bit error test was run for 72 hours. All other tests were run for more than 24 hours. No errors were seen in any of these tests, and all data transmitted was properly received. The test configuration for these tests is shown in Figure 1.
Jitter and Signal Integrity Tests
This test was done to ensure that the signal quality is acceptable when data is sent or received over 10m of UTP5 cable. This test was run with all line rates that the IDT77V1264L200 ATM PHY can operate with. Both Phys have fixed but separate oscillators (FOX 1100E).
The test configuration used was same as shown in Figure 1. The UTP5 cable connecting one system to another was changed for different lengths.
Bit error rate limit 1E-10 Pass / Fail Pass Pass Pass Pass Pass Pass Pass Pass
Cable Length 10m 10m 10m 10m 10m 10m 9m 9m
Oscilla tor 32Mhz 32Mhz 32Mhz 64Mhz 64Mhz 64Mhz 32Mhz 32Mhz
Multiplier 1x 2x 4x 1x 2x 4x 1x 2x
Line Rate 32Mbps 64Mbps 128Mbps 64Mbps 128Mbps 256Mbps 32Mbps 64Mbps
Jitter Spec Limit 4ns Pass / Fail Pass Pass Pass Pass Pass Pass Pass Pass
1.2ns 1.32ns 920ps 1.2ns 1.04ns 680ps 1ns 1.2ns

 
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