8 THVD1400 Capacitance Results

With the setup and conditions described previously, the waveforms with highest and lowest tested capacitance can be shown. Table 8-1 lists the voltage drop times for all single-ended and differential capacitance with D held at 0V.

For 50pF single-ended capacitance,Figure 8-1shows that the yellow nRE/DE line is switched from transmitting to receiving. The orange A-B line demonstrates the differential bus gradually pulling to a high voltage due to the RC constant. As a result, the R pin has a voltage drop that lasts 112ns.

Figure 8-1 THVD1400 50pF Single-ended Capacitance

Figure 8-2 shows that when a 1000pF single-ended capacitance is on the bus, a longer voltage drop of 189ns is seen. The A-B bus line requires more time to reach a steady voltage value.

Figure 8-2 THVD1400 1000pF Single-ended Capacitance

For differential capacitance of 50pF, the voltage drop lasts for 114ns in Figure 8-3.

Figure 8-3 THVD1400 50pF Differential Capacitance

For a differential capacitance of 1000pF, the voltage drop lasts for 284ns in Figure 8-4. Again, the A-B bus line can be seen taking more time to reach a voltage high. Hence, the longer voltage drop period.

Figure 8-4 THVD1400 1000pF Differential Capacitance

Table 8-1 shows that as the capacitance increases on the bus, the voltage drop time increases.