For this test the PWM frequency was increased to 100kHz, with a corresponding PWM period of 10µs. A sinusoidal three-phase voltage with a frequency of 25Hz and a peak-to-peak PWM duty cycle of 10% was impressed, as shown in Figure 4-13. The phase-W voltage was measured with a pigtail voltage probe, the phase current with a current probe. The modulator clock frequency was 20MHz. The bitstream was filtered with a sync³, OSR64 filter, which has a sampling window of 9.6µs. The sampling window of the delta-sigma modulator is almost as wide as the PWM period. Therefore PWM switching always occurs during the sampling time. Figure 4-14 shows the AMC0106M05 phase current measurement. Again, there is no effect of the PWM switching visible.

Figure 4-13 Scope Plot of Infinite Persistence Measurement of the Phase W Voltage

Figure 4-14 AMC0106M05 Phase Current I_W with OSR 64 at 100kHz PWM