TDA8932B Datasheet, PDF (24/48 Pages) NXP Semiconductors – Class-D audio amplifier

NXP Semiconductors
TDA8932B
Class-D audio amplifier
14.2 Output current limiting
The peak output current I_O(max) is internally limited above a level of 4 A (minimum). During
normal operation the output current should not exceed this threshold level of 4 A
otherwise the output signal is distorted. The peak output current in SE or BTL
configurations can be estimated using Equation 5 and Equation 6.
SE configuration:
I_O(max) ≤ -_R----_L----₊-----_R---_D---⁰-_S--^.-_o⁵--_n---^×-₊---^V--_R---^P-_s---₊-----_R----_E---_S---_R- ≤ 4 A
(5)
BTL configuration:
I_O(max) ≤ -_R----_L----₊----₂-----_×-----₍-^V-_R----^PD----_S--_o---_n----₊-----_R----_s--₎ ≤ 4 A
(6)
Where:
V_P = supply voltage V_DDP1 − V_SSP1 (V) or V_DDP2 − V_SSP2 (V)
R_L = load impedance (Ω)
R_DSon = on-resistance power switch (Ω)
R_s = series resistance output inductor (Ω)
R_ESR = equivalent series resistance SE capacitor (Ω)
Example:
A 4 Ω speaker in the BTL configuration can be used up to a supply voltage of 18 V without
running into current limiting. Current limiting (clipping) will avoid audio holes but it causes
a comparable distortion like voltage clipping.
14.3 Speaker configuration and impedance
For a flat frequency response (second-order Butterworth filter) it is necessary to change
the low-pass filter components Llc and Clc according to the speaker configuration and
impedance. Table 14 shows the practical required values.
Table 14. Filter component values
Configuration
SE
R_L (Ω)
4
6
8
BTL
4
6
8
Llc (µH)
22
33
47
10
15
22
Clc (nF)
680
470
330
1500
1000
680
14.4 Single-ended capacitor
The SE capacitor forms a high-pass filter with the speaker impedance. So the frequency
response will roll-off with 20 dB per decade below f_-3dB (3 dB cut-off frequency).
TDA8932B_4
Product data sheet
Rev. 04 — 18 December 2008
© NXP B.V. 2008. All rights reserved.
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