CS4525(2008) 查看數據表（PDF） - Cirrus Logic

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CS4525
(Rev.:2008)

30 W Digital Audio Amplifier with Integrated ADC

Cirrus Logic 

CS4525

6.4 Output Filters

The output filter configuration of the CS4525 can greatly affect device performance. These components re-

duce radiated EMI, protect the output transistors of the device, attenuate the high frequency content of the

output signal, and, in the half bridge configuration, block DC current from reaching the loudspeaker.

6.4.1

Half-Bridge Output Filter

Figure 26 shows the output filter for a half-bridge configuration. A transient voltage suppression circuit is

implemented as an RC snubber network comprised of a resistor Rs (5.6 Ω, 1/8 W) and a capacitor Cs

(680 pF). This should be placed as close as possible to the corresponding output pin. This circuit decreas-

es the slew rate of the output signal and reduces high frequency ringing which can lead to increased EMI.

The Schottky diodes protect the body diodes of the output devices by conducting load current during

switching transitions; these diodes must be present to ensure proper device operation.

VP

CS4525

OUTx

Cs

680 pF

Rs

5.6 Ω

D1*

L1

C2

D2*

* ROHM RB160 M-30 C1

or equivalent

Figure 26. Output Filter - Half-Bridge

The inductor L1 and capacitor C1 form a low-pass filter to remove high frequency switching content from

the output signal. These values combine with the nominal load impedance of the speaker to set the cut-

off frequency of the filter. Table 18 shows the component values for L1 and C1 based on nominal speaker

impedance for a corner frequency of approximately 35 kHz (-3 dB).

Load

4Ω

6Ω

8Ω

L1

22 µH

33 µH

47 µH

C1

1.0 µF

0.68 µF

0.47 µF

Table 18. Low-Pass Filter Components - Half-Bridge

C2 serves to block DC from the output. Table 19 shows the component values for C2 based on desired

corner frequency (-3 dB) and nominal speaker impedances of 4 Ω, 6 Ω, and 8 Ω. This capacitor should be

chosen to have a ripple current rating higher than the amount of current that will pass through it.

Load

4Ω

6Ω

8Ω

Corner Frequency

40 Hz

58 Hz

120 Hz

39 Hz

68 Hz

120 Hz

42 Hz

60 Hz

110 Hz

C2

1000 µF

680 µF

330 µF

680 µF

390 µF

220 µF

470 µF

330 µF

180 µF

Table 19. DC-Blocking Capacitors Values - Half-Bridge

DS726PP3

59

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