2 Results

During the load transient, the TPSM8A29 achieves an 84 mV peak-to-peak voltage transient with only 42 mV zero-to-peak (Figure 2-1) during the unload transient. The DCAP-3 control architecture featured in TPSM8A29 allows for a higher crossover frequency and lower overall output capacitance. Additionally, when the load is turned off, TPSM8A29 does not begin switching until the entire load has dropped to zero, minimizing the peak voltage to 40 mV.

By contrast, notice that TPS543B20 is not stable with 2 x 100-µF (Figure 2-2), and the superfluous switching during the unload step resulted in the zero-to-peak transient of 60 mV. This output is 20 mV higher than TPSM8A29 at the same position.

When the design was iterated to improve and the transient performance, increasing output capacitance to 3 x 100-µF finally allowed the TPS543B20 to achieve loop stability, but the load transient performance of -53 mV and +45 mV (Figure 2-3), with a total of 98 mV peak-to-peak was still greater than the TPSM8A29 with 2 x 100-µF.