TDA8932B Datasheet, PDF (25/48 Pages) NXP Semiconductors – Class-D audio amplifier

NXP Semiconductors
TDA8932B
Class-D audio amplifier
The 3 dB cut-off frequency is equal to:
f _–3dB = -₂---_π-----_×----_R----¹_L----_×-----_C-----_s--_e-
(7)
Where:
f_-3dB = 3 dB cut-off frequency (Hz)
R_L = load impedance (Ω)
Cse = single-ended capacitance (F); see Figure 36
Table 15 shows an overview of the required SE capacitor values in case of 60 Hz, 40 Hz
or 20 Hz 3 dB cut-off frequency.
Table 15. SE capacitor values
Impedance (Ω)
Cse (µF)
f_-3dB = 60 Hz
4
680
6
470
8
330
f_-3dB = 40 Hz
1 000
680
470
f_-3dB = 20 Hz
2 200
1 500
1 000
14.5 Gain reduction
The gain of the TDA8932B is internally fixed at 30 dB for SE (or 36 dB for BTL). The gain
can be reduced by a resistive voltage divider at the input (see Figure 10).
audio in
R1
470 nF
R2
R3
470 nF
100
kΩ
001aad762
Fig 10. Input configuration for reducing gain
When applying a resistive divider, the total closed-loop gain G_v(tot) can be calculated by
Equation 8 and Equation 9:
G_v(tot) = G_v(cl) + 20log -_R---_E----_Q----₊-----^R₍---_R^E----^Q₁----₊-----_R----₂----₎
(8)
Where:
G_v(tot) = total closed-loop voltage gain (dB)
G_v(cl) = closed-loop voltage gain, fixed at 30 dB for SE (dB)
R_EQ = equivalent resistance, R3 and Z_i (Ω)
R1 = series resistor (Ω)
R2 = series resistor (Ω)
TDA8932B_4
Product data sheet
Rev. 04 — 18 December 2008
© NXP B.V. 2008. All rights reserved.
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