CS43131 datasheet(28/156 Pages) CIRRUS

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DS1155F1

CS43131

4 Functional Description

This section describes the general theory of operation of the CS43131, tracing the signal and control flow through the

various blocks within the device. It comprises the following sections:

• Section 4.1, “Overview”

• Section 4.2, “Analog Outputs”

• Section 4.3, “Class H Amplifier Output”

• Section 4.4, “Alternate Headphone Inputs”

• Section 4.5, “Headphone Presence Detect and Output Load Detection”

• Section 4.6, “Clocking Architecture”

• Section 4.7, “Clock Output and Fractional-N PLL”

• Section 4.8, “Filtering Options”

• Section 4.9, “Audio Serial Port (ASP)”

• Section 4.10, “DSD Interface”

• Section 4.11, “DSD and PCM Mixing”

• Section 4.12, “Standard Interrupts”

• Section 4.13, “Control Port Operation”

• Section 4.14, “Programmable Filter”

4.1 Overview

4.1.1

Analog Outputs

The analog output block includes separate pseudodifferential headphone Class H amplifiers output. An on-chip inverting

charge pump creates a positive and negative voltage equal to the input, allowing an adaptable, full-scale output swing

centered around ground. The resulting internal amplifier supply can be ±VCP, or ±VP_LDO (either ±3.0 V with HV_EN = 1

or ±2.6 V with HV_EN = 0).

The inverting architecture eliminates the need for large DC-blocking capacitors and allows the amplifier to deliver more

power to HP loads at lower supply voltages. This adaptive power supply scheme converts traditional Class AB amplifiers

into more power-efficient Class H amplifiers.

4.1.2

Alternate Headphone Inputs

The alternate headphone inputs provide an integrated selectable path to interface between the system codec output and

the headphone connector, which allows for lower-power operation in applications such as voice or compressed music

playback. These inputs eliminate the need for an external audio switch and prevent the high-fidelity headphone outputs of

CS43131 from degradation by the external audio switch.

4.1.3

Headphone Detection

The CS43131 detects the presence of a headphone and notifies the application processor to wake up through an interrupt

event.

4.1.4

Headphone Impedance Measurement

The CS43131 detects headphone impedance information at low frequencies, which can be used to adjust the system

properly to accommodate different load conditions. One example is to adjust signal chain gain to avoid distortion.

The CS43131 also provides impedance measurement functions to evaluate the headphone load within 20 Hz to 20 kHz.

A specific frequency is selected and the impedance measurement process is initiated by setting the register. Through a

series of interrupt events, the CS43131 notifies application processor to retrieve the impedance information after

completion.

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