Table 13. Design Parameters

8.2.1.2.1 Audio Input/Output

The choice of digital or analog audio input is driven by system specific considerations. However, since a digital audio interface will typically be used to send current and voltage data from the TAS2552 to a system processor, using a bidirectional I²S interface is likely to be the best choice.

If a digital audio input is used, the analog inputs, IN+ and IN-, should be shorted together, and not tied to ground.

8.2.1.2.2 Mono/Stereo Configuration

In this application, the device is assumed to be operating in mono mode. See General I2C Operation for information on changing the I²C address of the TAS2552 to support stereo operation. Mono or stereo configuration does not impact the device performance.

8.2.1.2.3 Boost Converter Passive Devices

The boost converter requires three passive devices that are labeled L1, C1 and C2 in Figure 50 and whose specifications are provided in Table 12. These specifications are based on the design of TAS2552 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.

Specifically, the product of L1 and C2 (derated value at 8.5 V) has to be greater than 10e-12 for boost stability after accounting worst case variation of L1 and C2. To satisfy sufficient energy transfer, L1 needs to be > 2 µH at the boost switching frequency (~1.75 MHz). Minimum C2 (derated value at 8.5 V) should be > 4 µF for Class-D power delivery specification. The saturation current for L1 should be > ILIM to deliver Class-D peak power.

8.2.1.2.4 EMI Passive Devices

The TAS2552 supports edge-rate control to minimize EMI, but the system designer may want to include passive devices on the Class-D output devices. These passive devices that are labeled L2, L3, C3 and C4 in Figure 50 and their recommended specifications are provided in Table 12. If C3 and C4 are used, they must be placed after L2 and L3 respectively to maintain the stability of the output stage.

8.2.1.2.5 Miscellaneous Passive Devices

• VREG Capacitor: Needs to be 10 nF to meet boost and class-D power delivery and efficiency specs.
• BIAS Capacitor: Needs to be 1 µF to meet PSSR and noise performance.

Table 14. Design Parameters

8.2.2.2.1 Audio Input/Output

In this application, system considerations require the use of an analog audio input. Note that a digital audio interface, such as I²S, still needs to be connected to send current and voltage data from the TAS2552 to a system processor.

The analog inputs to TAS2552 should be ac-coupled to the device terminals to allow decoupling of signal source's common mode voltage with that of TAS2552's common mode voltage. The input coupling capacitor in combination with the selected input impedance of TAS2552 forms a high-pass filter.

Figure 56. Analog Input Connection

For high fidelity audio playback, it is desirable to keep the cutoff frequency of the high pass filter below the minimum reproducible frequency of the speaker. For example, a 1 µF capacitor connected to the differential analog inputs with input resistance 10 kΩ results in a cutoff frequency of 16 Hz.

Table 16. Design Parameters