Design Considerations for Analog Input Class D

Output power per channel ? The maximum output power mainly depends on the power supply (output voltage and current) and the impedance of the speaker. ? The typical efficiency of Class D amplifiers is between 80% and 0%, reducing the need for power supply design. ? The maximum input signal level specifies the required power amplifier gain to meet the required output power. ? In order to optimize the suppression of noise, the gain should be as small as possible. Output filter design ? When the speaker line is shorter than 10cm, most Class D amplifiers can operate without filters. ? When the speaker line is long, you can configure a second-order low-pass (LC) filter and make it as close as possible to the output pin of the filter. ? The filter must be designed for the specific speaker resistance, because the impedance of the load will affect the quality factor of the filter, the Q value. ? Ferrite beads can also eliminate UHF interference. Printed circuit board (PCB) wiring ? The decoupling capacitor and output filter should be placed as close as possible to the amplifier chip. ? When using a ferrite bead filter, the LC filter should be placed as close to the chip as possible. ? Always connect PowerPAD ? terminals to power ground ? When the PowerPAD packaged device in the amplifier system uses a central 'star' ground, only a single connection point should be used to connect the analog ground to the power ground