CS44800 datasheet(35/81 Pages) CIRRUS

35 / 81 page

DS632PP1

CS44800

4.5.10

Power Supply Rejection (PSR) Real-Time Feedback

Inherent to most Class D power amplifier solutions is the requirement for a clean and well-regulated high

voltage power supply. Any noise or tones present on the power rail will couple through each channel’s

power MOSFET output device. These spurious distortion components on the output signal consist of dis-

crete tones, which can be audible from the speaker, and tones that modulate around the audio signal be-

ing played.

To remove the requirement for a well-regulated power supply, and therefore reduce overall system costs,

the rejection of harmonic distortion from the power supply and tones coupled onto the power rail is ac-

complished by the patented power supply rejection realtime feedback. By using the CS4461 and associ-

ated attenuation circuitry, the scaled AC and DC components of the power supply rail are fed back into

the PWM modulator. All delays through the feedback path have been minimized such that the noise can-

cellation is accomplished in real-time allowing for substantial noise rejection within the output audio signal.

See “Typical Connection Diagrams” on page 22 for examples on how to connect the external ADC

(CS4461) to the CS44800 for PSR feedback, “Recommended PSR Calibration Sequence” on page 44,

and the CS4461 datasheet.

CS44800 Datasheet(PDF) 35 Page - Cirrus Logic