TDA8933B 데이터 시트보기 (PDF) - NXP Semiconductors.

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TDA8933B

Class-D audio amplifer

NXP Semiconductors. 

NXP Semiconductors

TDA8933B

Class D audio amplifier

14.4 Single-ended capacitor

The SE capacitor forms a high-pass filter with the speaker impedance. This means that

the frequency response will roll off with 20 dB per decade below f−3dB and a cut-off

frequency of 3 dB.

The 3 dB cut-off frequency is equal to:

f –3dB = 2----π-----×----R----1L----×-----C-----S--E--

(7)

Where:

• f−3dB = 3 dB cut-off frequency (Hz)

• RL = load resistance (W)

• CSE = single-ended capacitance (F); see Figure 32

Table 15 shows an overview of the required SE capacitor values in the case of a 60 Hz,

40 Hz or 20 Hz 3 dB cut-off frequency.

Table 15. SE capacitor values

Impedance (Ω)

4

CSE (µF)

f−3dB = 60 Hz

680

6

470

8

330

f−3dB = 40 Hz

1000

680

470

f−3dB = 20 Hz

2200

1500

1000

14.5 Gain reduction

The gain of the TDA8933B is internally fixed at 30 dB for SE and 36 dB for BTL. The gain

can be reduced by a resistive voltage divider at the input (see Figure 9).

audio in

R1

470 nF

R2

R3

470 nF

Fig 9. Input configuration for reducing gain

100

kΩ

010aaa137

When applying a resistive divider, the total voltage gain Gv(tot) can be calculated using

Equation 8 and Equation 9:

Gv(tot) = Gv(cl) + 20log -R---E----Q----+-----R(---RE----Q1----+-----R----2----)

(8)

TDA8933B_1

Preliminary data sheet

Where:

• Gv(tot) = total voltage gain (dB)

• Gv(cl) = closed-loop voltage gain, fixed at 30 dB for SE (dB)

• REQ = equivalent resistance, R3 and Zi (Ω)

Rev. 01 — 23 October 2008

© NXP B.V. 2008. All rights reserved.

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