CRD4412 Cirrus Logic, Inc., CRD4412 Datasheet - Page 16

• Manufacturer Part Number: CRD4412
• Description: 60 W Quad Half-bridge Digital Amplifier Power Stage
• Manufacturer: Cirrus Logic, Inc.

16
4.4
4.4.1
Output Filter
The RC filter placed after the PWM outputs can greatly affect the output performance. The filter not only
reduces radiated EMI (snubber filter) but also filters high-frequency content from the switching output before
going to the speaker (low-pass filter).
Half-Bridge Output Filter
Figure 5
(snubber circuit) is comprised of a resistor (5.6 Ω , 1/8 W ) and capacitor (560 pF) and should be placed as
close as possible to the corresponding PWM output pin. This will greatly reduce radiated EMI.
The inductor, L1, and capacitor, C1, comprise the low-pass filter. Along with the nominal load impedance
of the speaker, these values set the cutoff frequency of the filter.
L1 and C1 based on nominal speaker (load) impedance for a corner frequency (-3 dB point) of approxi-
mately 35 kHz.
C2 is the DC-blocking capacitor.
3 dB point) and a nominal speaker (load) impedance of 4 Ω . This capacitor should also be chosen to have
a ripple current rating above the amount of current that will pass through it.
shows the output filter for a half-bridge configuration. The transient-voltage suppression circuit,
Output
PWM
Table 3. DC-Blocking Capacitors Values - Half-Bridge
Table 2. Low-Pass Filter Components - Half-Bridge
Figure 5. Output Filter - Half-Bridge
560 pF
4 Ω
6 Ω
8 Ω
5.6 Ω
Corner Frequency
Load
Table 3
110 Hz
36 Hz
54 Hz
shows the component values for C2 based corner frequency (-
22 µH
33 µH
47 µH
VP
*Diode is Zetex
L1
ZHCS400 or
equivalent
1000 µF
680 µF
330 µF
0.68 µF
0.47 µF
L1
1.0 µF
C2
C1
Table 2
+
C1
C2
-
shows the component values for
CS44130
DS690PP1