CS35L32 datasheet(16/51 Pages) CIRRUS

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DS963F5

CS35L32

4.3 Speaker Amplifier

To clear any status bits set due to the initiation of a path or block, all interrupt status bits should be read after reset and

before normal operation begins. Otherwise, unmasking these previously set status bits causes INT to assert.

4.3 Speaker Amplifier

The CS35L32 features a high-efficiency mono Class D audio amplifier, shown in Fig. 4-2, with an advanced closed-loop

architecture that achieves low levels of output distortion. Automatic Class G operation, using a boosted supply to the

amplifier, allows louder speaker performance with high crest factor.

Figure 4-2. Speaker Amplifier Block Diagram

4.3.1

Class G Operation with LEDs Off

The boost converter output is the supply to the speaker amplifier. Audio operation can be programmed to have one of the

following supply modes (See Section 7.12 for programming details.):

• Class G where the boost converter is in Bypass Mode for audio input signals below a threshold VIN1THON and in

5-V Boost Mode for audio signal inputs above a threshold VIN1THOFF. These thresholds are specified in Table 3-4

for the given conditions. The corresponding equations are shown below.

• Class G disabled, boost converter is in Bypass Mode, and VBST = VP. In this mode, thresholds are ignored.

• Class G disabled, boost converter is in Boost Mode, and VBST = 5 V. In this mode, thresholds are ignored.

The Class G equations for the audio input signal thresholds are as follows:

VBST is the boost converter output voltage (whether in Bypass or Boost Mode), and gain is audio gain expressed as a

unitless real ratio (nonlogarithmic). K = 1 if MCLK is 6 or 12 MHz; K = 1.024 if MCLK is 6.144 or 12.288 MHz. MCLKINT

should be configured as described in Section 4.13.1 and Section 7.7.

Table 4-1. Interrupt Status Registers and Corresponding Mask Registers

Status Registers

Mask Registers

Interrupt Status 1 (Audio) (Section 7.19)

Interrupt Status 2 (Monitors) (Section 7.20)

Interrupt Status 3 (LEDs and Boost Converter) (Section 7.21)

Interrupt Mask 1 (Section 7.16)

Interrupt Mask 2 (Section 7.17)

Interrupt Mask 3 (Section 7.18)

and

Hybrid Class D Audio Amplifier

(PDN_AMP = 0)

Hybrid Class D Modulator

-Class D

Modulator

9–18 dB

Short

Circuit

Protection

SPKOUT+

SPKOUT–

Hybrid Class D

Power Stage

VBST

IN+

IN–

AMP_GAIN p. 39

GAIN_CHG_ZC p. 39

AUDIOGAIN_MNG p. 38

IN1THOF

------K





VBST

Gain

-----------------







IN1THON

---K





VBST

Gain

-----------------







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