cs4412 Cirrus Logic, Inc., cs4412 Datasheet - Page 15

• Manufacturer Part Number: cs4412
• Description: 30 W Quad Half-bridge Digital Amplifier Power Stage Logic
• Manufacturer: Cirrus Logic, Inc.

DS749A1
4.4
4.4.1
Output Filters
The 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 LC filter).
Half-Bridge Output Filter
Figure 5
(snubber circuit) is comprised of a resistor (20 Ω, ¼ W) and capacitors (220 pF) and should be placed as
close as possible to the corresponding PWM output pin to 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) impedances of 4 Ω, 6 Ω, and 8 Ω. This capacitor should also
be chosen to have a ripple current rating above the amount of current that will passed through it.
shows the output filter for a half-bridge configuration. The transient-voltage suppression circuit
Output
PWM
Table 3. Low-Pass Filter Components - Half-Bridge
Load
4 Ω
6 Ω
8 Ω
Table 4
Figure 5. Output Filter - Half-Bridge
220 pF
20 Ω
shows the component values for C2 based on corner frequency
22 µH
33 µH
47 µH
L1
VP
*Diode is Zetex
ZHCS400 or
equivalent
L1
Table 3
0.68 µF
0.47 µF
1.0 µF
C1
shows the component values for
+
C1
C2
-
CS4412
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