Cirrus Logic CS35L03 - Manual (Page 15)

CS35L01/03
DS909F1 15
5. APPLICATIONS
5.1 MODE Descriptions
The CS35L01/03 devices can be operated in one of four operating modes, determined by the MODE pin
and the LFILT+ pin. The four modes of operation are Standard Class-D operation (SD), Reduced Frequency
Standard Class-D operation (FSD), Hybrid Class-D operation (HD), and Reduced Frequency Hybrid Class-
D operation (FHD). Each of these modes can be leveraged to optimize different performance criteria in an
array of applications.
Table 1. LFILT+ and MODE Operation Configurations
5.1.1 Standard Class-D Modes of Operation
5.1.1.1 SD Mode
Standard Class-D (SD) mode supports full audio bandwidth with very good SNR and THD+N perfor-
mance. This mode of operation is characterized by a traditional closed loop, analog
 modulated Class-
D amplifier. With an output switching frequency of 192 kHz, this mode ensures flat frequency response
across the entire audio frequency range.
5.1.1.2 FSD Mode
The Reduced Frequency Class-D (FSD) mode provides competitive audio performance and a reduction
in radiated emissions by decreasing the switching frequency of the output devices to 76 kHz. This reduc-
tion in switching frequency reduces the high-frequency energy being created by the output switching
events. Idle channel noise is slightly higher in this mode of operation than SD mode, with the trade-off
being better EMI performance and power consumption.
5.1.2 Hybrid Class-D Modes of Operation
Hybrid Class-D and Reduced Frequency Hybrid Class-D modes of operation allows the rail voltage for the
output devices to switch between a high voltage net and a low voltage net depending on the audio content
being amplified. This is explained in more detail in
Section 5.1.2.1 and Section 5.1.2.2 . Operation in these
modes requires that the voltage present on the VBATT pin be above the level listed as “VBATT Limit for
HD/FHD Mode (VB
LIM
)” in “Electrical Characteristics - All Operational Modes” on page 9 . If it is not, HD
and FHD modes of operation of the device will automatically be disabled and operation will be limited to
the SD mode of operation.
MODE connected to:
GND VBATT
LFI
L
T
+ co
nn
e
c
te
d
to
:
VBATT
Reduced Frequency Class-D Mode
(FSD)
Standard Class-D Mode
(SD)
Filter Cap to Ground
Reduced Frequency Hybrid Class-D Mode
(FHD)
Hybrid Class-D Mode
(HD)