Adding capacitance across the bus lines attenuates transients by providing a low-impedance path for high-frequency energy. If adding additional beads to improve the EMI performance, use the following recommendations:

• Add a differential capacitor (R2 to R1) with values larger than 220pF and place as close as possible to the transceiver pins. Figure 4-1 presents simulation results with the bus capacitor (CAP_LOAD) from 20pF to 620pF.
• Add capacitors to ground on each bus line. Figure 4-2 presents the actual waveform after adding the bus capacitor of 390pF to GND each other.

This workaround can have slight impact on signal integrity, so TI recommends users test on boards to verify signal integrity. Figure 4-3 shows the rise and fall time increase from approximately 18ns to approximately 40ns at 620pF total, and 10Mbps of communication remains fully supported.

Figure 4-1 Simulation Results: Effect of CAP_LOAD from 20pF to 620pF

Figure 4-2 Test Results: No Glitch After Increasing Bus Capacitor

Figure 4-3 Simulation Results: Effect of Increasing CAP_LOAD (120pF and 620pF)