Cirrus Logic CS35L00 - Manual (Page 15)

CS35L00
DS906PP1 15
5. APPLICATIONS
5.1 MODE Descriptions
The CS35L00 device 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
ΔΣ 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)