Cirrus Logic CS35L32 - Manual (Page 16)

16 DS963F4
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 V
IN1THON
and in
5-V Boost Mode for audio signal inputs above a threshold V
IN1THOFF
. 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. MCLK
INT
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
V
IN1THOF
4
15
------K
 
  VBST
Gain
-----------------
 
 
 =
V
IN1THON
2
3
---K
 
  VBST
Gain
-----------------
 
 
 =