9.2.2.2 Boost Converter Passive Devices

The boost converter requires three passive devices that are labeled L1, C1 and C2 in and whose specifications are provided in Table 320. These specifications are based on the design of the TAS2564 and are necessary to meet the performance targets of the device. In particular, L1 should not be allowed to enter in the current saturation region. The saturation current for L1 should be > ILIM to deliver Class-D peak power.

Additionally, the ratio of L1/C2 (the derated value of C2 at 11.5 V should be used in this ratio) has to be lesser than 1/3 for boost stability. This 1/3 ratio should be maintained including the worst case variation of L1 and C2. To satisfy sufficient energy transfer, L1 needs to be ≥ 0.47 μH at the boost switching frequency (100 kHz to 4 MHz). Using a 0.47μH will have more boost ripple than a 1.0 μH or 2.2 μH but the high PSRR should minimize the effect from the additional ripple. Finally, the minimum C2 (derated value at programmed boost voltage) should be > 3.3 μF for Class-D power delivery specification.